JP3489533B2 - Optical head device and optical information recording / reproducing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device and an optical information recording / reproducing device, and more particularly to an optical head device and an optical device for performing recording / reproducing on an optical recording medium of a land / groove recording system. The present invention relates to a formula information recording / reproducing apparatus.

[0002]

2. Description of the Related Art As one of methods for increasing the density of an optical information recording / reproducing apparatus, recording / reproducing is performed on both a land, which is a concave portion of a groove, and a groove, which is a convex portion, of an optical recording medium. Performing land / groove recording is known.

In an optical information recording / reproducing apparatus for performing land / groove recording, when a land (or groove) of an optical recording medium is accessed, a focused spot is a land of the optical recording medium in order to prevent malfunction of track servo. It is desirable to perform the track servo pull-in operation after confirming that the track servo is positioned above (or the groove). For this reason,
A function (land / groove position detection function) of detecting whether the focused spot is located on the land or the groove of the optical recording medium is required.

FIG. 20 shows the structure of a conventional optical head device having a land / groove position detecting function. This optical head device is described in Japanese Patent Application Laid-Open No. 9-288831. The light emitted from the semiconductor laser 174 is collimated by a collimator lens 175, and split by a diffractive optical element 176 into three lights of 0th order light and ± 1st order diffracted light. These lights are incident as P-polarized light on the polarization beam splitter 177, almost 100% of them are transmitted, are transmitted through the quarter-wave plate 178, are converted from linearly polarized light to circularly polarized light, and are collected on the disc D1 by the objective lens 179. Be illuminated.

Further, the three reflected lights from the disk D1 are transmitted through the objective lens 179 in the opposite directions, and the quarter wave plate 1
After passing through 78, the circularly polarized light is converted into a linearly polarized light whose polarization direction is orthogonal to the forward path, is incident on the polarization beam splitter 177 as S-polarized light, and almost 100% thereof is reflected, and is transmitted through the cylindrical lens 181 and the spherical lens 182. The light is received by the photodetector 183. The photodetector 183 is installed in the middle of the two focal lines of the cylindrical lens 181 and the spherical lens 182.

FIG. 21 shows the arrangement of focused spots on the disk D1. Focused spots L185, L186, L18
7 is the 0th order light from the diffractive optical element 176, +1
It corresponds to the 1st-order diffracted light and the -1st-order diffracted light, and has a focused spot L18.
5 is on the track 184 (for example, land), the focused spot L186 is on the boundary between the track 184 and the track (groove) adjacent to the left side thereof, and the focused spot L187.
Are arranged on the boundary between the track 184 and the track (groove) adjacent to the right side thereof.

FIG. 22 shows the pattern of the light receiving portion of the photodetector 183 and the arrangement of light spots on the photodetector 183. The light spot L196 corresponds to the 0th-order light from the diffractive optical element 176, and is divided into four by a dividing line parallel to the tangential direction and a dividing line parallel to the radial direction of the disc D1 passing through the optical axis. The light is received at ˜191.

The light spot L197 is a diffractive optical element 176.
Disk D1 corresponding to the + 1st order diffracted light from
The light is received by the light receiving portions 192 and 193 which are divided into two by a dividing line parallel to the tangential direction. Light spot L
Reference numeral 198 corresponds to the −1st order diffracted light from the diffractive optical element 176, and the light receiving portions 194 and 195 are divided into two by a dividing line parallel to the tangential direction of the disc D1 passing through the optical axis.
Is received by.

Here, the focused spot L on the disk D1
Although the rows 185 to L187 are almost in the tangential direction, the light spot L19 is formed on the photodetector 183 by the action of the cylindrical lens 181 and the spherical lens 182.
6 to L198 are arranged substantially along the radial direction.

When the outputs from the light receiving sections 188 to 195 are represented by V188 to V195, the focus error signal is {(V188 + V191)-(V
189 + V190)}. The track error signal is {(V188 + V19
0)-(V189 + V191)}.

Further, the land / groove discrimination signal is
It is obtained from the calculation of {(V192 + V195)-(V193 + V194)}. Further, the reproduction signal from the focused spot L185 is (V188 + V189 + V190 + V19
It is obtained from the calculation of 1).

FIG. 23 shows various waveforms related to the track error signal and the land / groove discrimination signal. The horizontal axis represents the positional deviation amount between the focused spot L185 and the groove when the focused spot L185 traverses the groove of the disk D1 from the left side to the right side of FIG. 21, and a indicates that the focused spot L185 is located on the groove. The state, b is the state where the condensed spot L185 is located on the boundary between the groove and the land, c is the state where the condensed spot L185 is located on the land, and d is the state where the condensed spot L185 is the boundary between the land and the groove. It corresponds to each of the states located above.

A push-pull signal by the focused spot L185, that is, a track error signal {(V188 +
The waveform of (V190)-(V189 + V191)} is shown in FIG.
It becomes like (A).

The focused spot L186 is the focused spot L1.
2 for the 1/4 cycle of the groove of the disk D1 with respect to 85 in FIG.
Since it is arranged on the left side of 1, the focused spot L
186 is a push-pull signal (V192-V1
The waveform of (93) has a phase of π / with respect to the waveform of FIG.
It is delayed by 2 and becomes as shown in FIG.

The focused spot L187 is the focused spot L1.
2 for the 1/4 cycle of the groove of the disk D1 with respect to 85 in FIG.
Since it is arranged on the right side of 1, the focused spot L
187 push-pull signal (V194-V1
The waveform of (95) has a phase of π / with respect to the waveform of FIG.
It advances by 2 and becomes like FIG. 23 (C).

Since the waveforms in FIGS. 23B and 23C have opposite phases, the difference between the push-pull signals by the condensing spots L186 and L187, that is, the land / groove discrimination signal {(V192 + V195)- (V193 + V
The waveform of (194)} is as shown in FIG.

When the focused spot L185 is located on the groove of the disc D1, the track error signal shown in FIG. 23 (A) is 0, but the land / groove discrimination signal shown in FIG. 23 (D). Takes a positive value. On the other hand, when the focused spot L185 is located on the land of the disc D1, the track error signal shown in FIG. 23A is 0, but the land / groove discrimination signal shown in FIG. Takes a negative value. Therefore, it is possible to detect which of the land and the groove of the disc D1 the focused spot L185 is located on the basis of the sign of the land / groove discrimination signal.

[0018]

In the conventional optical head device shown in FIG. 20, since the land / groove positions are detected, the condensing spots L186 and L187 at both ends are compared with the condensing spot L185 at the center of the disk. The grooves of D1 are arranged so as to deviate from each other by ¼ cycle (half the land width or the groove width) in opposite directions. However, for a disc having a different track pitch from the disc D1, 3
Since the two condensing spots L185 to L187 cannot be arranged in this manner, the land / groove position cannot be detected.

On the other hand, as an optical head device capable of detecting the land / groove position on a disc having an arbitrary track pitch, there is an optical head device described in Japanese Patent Laid-Open No. 11-134677. However, in this optical head device, since the diffractive optical element divided into a plurality of regions by the dividing line is used, the diffractive optical element for aligning the dividing line at a predetermined position with respect to the optical axis of the incident light. It is extremely difficult to adjust the position within the plane.

[0020]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in a conventional optical head device having a land / groove position detection function, and to detect the land / groove position for a disc having an arbitrary track pitch. It is also possible to provide an optical head device and an optical information recording / reproducing device in which the position of an optical element can be easily adjusted.

[0021]

An optical head device and an optical information recording / reproducing device according to the present invention include a light source section for emitting a main beam and a sub beam, and an objective lens for converging each beam on an optical recording medium. , And a photodetector for receiving the reflected light from the optical recording medium.

Further, the light source section sets the distance from the objective lens of the main beam and the sub beam to the condensing point at least 0.1 to 1.0 [μ in the radial direction of the optical recording medium.
[m]] . This optical element shifts the focal point in the optical axis direction within the cross section including the optical axis and the radial direction, and does not shift the focal point position along the radial direction.

Further, the photodetector is provided with a light receiving portion for each of the main beam and the sub beam, and the light receiving portion for the sub beam individually receives the central portion and both end portions of the sub beam in the radial direction.

According to the above construction, since the focused spot of the main beam is focused on the optical recording medium, the focused spot is located on the land even when it is located on the groove of the optical recording medium. Even in this state, the intensity distribution in the radial direction of the main beam reflected by the optical recording medium is the same.

On the other hand, since the converging spot of the sub-beam is formed on the optical recording medium in a state where the converging point is deviated from the optical recording medium, the converging spot is on the land of the optical recording medium. The intensity distribution in the radial direction of the sub-beam reflected by the optical recording medium is different between the central portion and both end portions in the radial direction when the sub beam is reflected by the optical recording medium. That is, in a state in which the converging point is located far away or in front of the optical recording medium, the intensity of the peripheral portion becomes relatively stronger than the intensity of the central portion in the radial direction of the optical recording medium, or The strength of the peripheral portion becomes relatively weaker than the strength of the central portion in the radial direction. Therefore, a land / groove discrimination signal is obtained from the difference between the intensity of the central portion and the intensity of the peripheral portion of the sub beam reflected by the optical recording medium in the radial direction of the optical recording medium.

According to the above structure, it is not necessary to irradiate the sub beam by shifting the land width or the groove width by half in the radial direction as in the conventional case. For example, the main beam and the sub beam are irradiated on the same track. However, since the land / groove can be discriminated, it can be applied to various optical recording media regardless of the track pitch.

It should be noted that the above-mentioned sub-beams may have their light-converging points displaced at least in the radial direction as compared with the main beam, and the light-converging points in the tangential direction may coincide (for example, light-condensing). If the spot has astigmatic difference).

Further, in the optical information recording / reproducing apparatus having the optical head device having the above-mentioned structure, when the land (or groove) of the optical recording medium is accessed, the main beam is condensed in order to prevent runaway of the track servo. The track servo pull-in operation is performed after confirming that the spot is located on the land (or groove) of the optical recording medium.

Further, in the optical head device and the optical information recording / reproducing device of the present invention, a single area is used as an optical element for slightly defocusing the focused spot of the sub beam in the radial direction on the optical recording medium. Since it is possible to use an optical element made of, it is easy to adjust the position within the plane of the optical element.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS. 1 to 1
A first embodiment of the present invention will be described based on 2. Figure 1
FIG. 1 shows a block diagram of the optical information recording / reproducing apparatus 1 according to this embodiment. The optical information recording / reproducing apparatus 1 includes an optical head device 10, a head driving means (not shown) for performing focusing and tracking via the optical head device 10, and an operation control means 200 for the head driving means.
A signal processing circuit 201 for generating a track error signal, a focus error signal, a land / groove discrimination signal, and a reproduction signal based on the output of a photodetector 11 described later.

The optical head device 10 has a light source section 202 for emitting a main beam and a sub beam. The light source unit 202 includes a semiconductor laser 7 as a light source that emits a single laser beam, a collimator lens 2 that collimates the emitted light of the semiconductor laser 7, and a 0th order light that is the main beam of the collimated light. , And a diffractive optical element 3 which divides the light into three beams of ± first-order diffracted light which are sub-beams.

Further, the optical head device 10 converts the polarization beam splitter 4 for transmitting each beam and the transmission light of the polarization beam splitter 4 from linearly polarized light to circularly polarized light.
The 1/4 wavelength plate 5 and the transmitted light of the 1/4 wavelength plate 5 are recorded on the disk D.
1. An objective lens 6 for converging light on 1, a photodetector 11 for receiving the reflected light from the disc D1 on a light receiving surface divided into a plurality of predetermined light receiving portions, and outputting each light intensity, and in front of the photodetector. And a hologram optical element 8 which splits the reflected light and guides it to each light receiving portion of the photodetector 11.

With this configuration, each beam emitted from the light source unit 202 is incident on the polarization beam splitter 4 as P-polarized light and almost 100% thereof is transmitted, and is transmitted through the 1/4 wavelength plate 5 to be linearly polarized light to circularly polarized light. Is converted into a light beam and is condensed on the disk D1 by the objective lens 6. The three reflected lights from the disc D1 are transmitted through the objective lens 6 in opposite directions, and the 1/4 wavelength plate 5
Is transmitted to convert the circularly polarized light into linearly polarized light whose polarization direction is orthogonal to the outward path, is incident on the polarization beam splitter 4 as S-polarized light, and almost 100% is reflected, and most of the + 1st-order diffracted light is reflected by the hologram optical element 8. The light is diffracted, passes through the lens 9, and is received by the photodetector 11.

The diffractive optical element 3 will be described in detail with reference to FIGS. FIG. 2 is a plan view of the diffractive optical element 3.
The diffractive optical element 3 includes an objective lens 6 shown by a dotted circle in the figure.
The diffraction grating is formed in a region including the effective diameter of The direction of the grating in the diffraction grating is substantially parallel to the radial direction R (radial direction) of the disc D1 and the pattern of each grating is set in a concentric arc shape. The center of each arc is located outside the diffractive optical element 3 and below the tangential direction T (tangential direction) of the disc D1.

When the phase difference between the line portion and the space portion of the grating is, for example, 0.232π, the incident light is about 0 as 0th order light.
7.3% is transmitted, and about ± 5th order diffracted light is about 5.
1% is diffracted. If the light diffracted to the upper side of FIG. 2 is the + 1st order diffracted light and the light diffracted to the lower side of FIG. 2 is the −1st order diffracted light, the diffractive optical element 3 functions as a concave lens for the + 1st order diffracted light, It acts as a convex lens for the −1st order diffracted light.

FIG. 3 shows the arrangement of focused spots on the disk D1. 3A is a plan view seen from the direction of irradiating the disk D1 with laser light, and FIG. 3B is a side sectional view seen from the right side of FIG. 3A. Focused spots L12, L
Reference numerals 13 and 14 respectively correspond to the 0th-order light, the + 1st-order diffracted light, and the -1st-order diffracted light from the diffractive optical element 3, and FIG.
As shown in FIG. 3, the three focused spots L12 to L14 are arranged on the same track D2 (here, a groove). Since the diffractive optical element 3 has a lens power, the focused spot L12 which is the main beam is focused on the disk D1 as shown in FIG. 3B, but the focused spot L12 which is the sub-beam. L13 and L14 are slightly defocused on the disc D1.

That is, in the diffractive optical element 3 described above, the distance from the objective lens 6 to the focusing point when focusing each beam on the disk D1 is extended longer than the 0th order light for the + 1st order diffracted light. The -1st-order diffracted light has a function of being shorter than the 0th-order light. Therefore, the focused spot L1
3 is located in front of the condensing point when viewed from the incident side, and the condensing spot L14 is located farther than the condensing point when viewed from the incident side. The difference in distance between the main beam and each sub-beam from the objective lens 6 to the focal point is 0.1 in this embodiment.
It is about 1.0 [μm], preferably about 0.5 [μm]. In this way, since the distance from the objective lens 6 to the converging point is deviated, the converging spots L13 and L1 which are the sub-beams.
4 has a slightly larger diameter than the focused spot L12 that is the main beam.

As shown in FIG. 3A, the direction of the diffractive optical element 3 is set so that the respective focused spots L12, L13, L14 are lined up on the same track D2 of the disc D1. .

Next, the hologram optical element 8 described above will be described in detail. FIG. 4 is a plan view of the hologram optical element 8. The hologram optical element 8 has a configuration in which diffraction gratings are formed on both the surface on which light is incident (incident surface) and the surface on which light is emitted (emission surface). FIG. 4A is a plan view of the incident surface as seen from the light incident side. The diffraction grating formed on the incident surface includes the effective diameter of the objective lens 6 shown by a dotted circle in the figure, and is divided into two regions 15 and 16 by a dividing line parallel to the radial direction R of the disc D1. .

The direction of the grating in the diffraction grating is the region 15,
All of 16 are parallel to the tangential direction T of the disk D1, and the pattern of the lattice is a straight line at equal intervals in both regions 15 and 16. Further, the lattice intervals in the regions 15 and 16 are equal.

Further, the cross-sectional shape of the lattice is the regions 15 and 16.
In any of the above, it is serrated. When the phase difference between the upper and lower portions of the sawtooth is 2π, almost 100% of the incident light on each region is diffracted as + 1st order diffracted light. Area 15
The direction of the sawteeth is set so that the light diffracted to the left side of the figure becomes the + 1st order diffracted light, and the direction of the sawtooth in the area 16 is set so that the light diffracted to the right side of the figure becomes the + 1st order diffracted light. Has been done.

On the other hand, FIG. 4B is a plan view of the exit surface as seen from the side on which light is incident. The diffraction grating formed on the exit surface includes the effective diameter of the objective lens 6 shown by the dotted circle in the figure,
It is divided into four regions 17 to 20 by three dividing lines parallel to the tangential direction T of the disc D1.

The direction of the grating in the diffraction grating is from region 17 to
20 is parallel to the tangential direction T of the disk D1, and the grid pattern is a straight line at equal intervals in all of the regions 17 to 20. The regions 17 and 20 have the same lattice spacing, and the regions 18 and 19 have the same lattice spacing. And the former is narrower than the latter.

Further, the cross-sectional shape of the lattice is the regions 17 to 20.
In any of the above, it is serrated. If the phase difference between the upper and lower parts of these saw teeth is 2π, the incident light to each area is +1.
Almost 100% is diffracted as the secondary diffracted light. The directions of the saw teeth in the areas 17 and 18 are set so that the light diffracted to the left side of the figure becomes the + 1st order diffracted light, and the direction of the saw teeth in the areas 19 and 20 is the + 1st order of the light diffracted to the right side of the figure. It is set to be the best light. In addition,
The diffraction grating formed on the entrance surface and the diffraction grating formed on the exit surface of the hologram optical element 8 can be replaced with each other.

Next, the photodetector 11 described above will be described in detail. FIG. 5 shows the pattern of the light receiving portion of the photodetector 11 and the arrangement of the light spots on the photodetector 11.

Among the light receiving parts of the photodetector 11, the light receiving parts 21 to 21
Reference numeral 28 denotes a light receiving section for the main beam, and the light receiving sections 21 to 24
Is a light receiving section for the + 1st order diffracted light by the area 15 of the hologram optical element 8, and the light receiving sections 25 to 28 are light receiving sections for the + 1st order diffracted light by the area 16. Each of the light receiving portions 21 to 24 and the light receiving portions 25 to 28 is formed by being divided into four by a dividing line along the tangential direction T and a dividing line along the radial direction R in which rectangular light receiving portions intersect with each other. There is.

On the other hand, the light spot L41 is the + 1st-order diffracted light from the region 15 of the hologram optical element 8 out of the 0th-order light from the diffractive optical element 3 and the + 1st-order diffracted light from the region 17.
It corresponds to the next-order diffracted light and is condensed on the boundary line between the light receiving units 21 and 22.

The light spot L42 is the + from the region 15 of the hologram optical element 8 in the 0th order light from the diffractive optical element 3.
It is the first-order diffracted light and corresponds to the + 1st-order diffracted light from the region 18, and is condensed on the boundary line between the light receiving units 21 and 22.

The light spot L43 is + from the area 15 of the hologram optical element 8 in the 0th order light from the diffractive optical element 3.
It is the first-order diffracted light and corresponds to the + 1st-order diffracted light from the region 19, and is condensed on the boundary line between the light receiving portions 23 and 24.

The light spot L44 is + from the area 15 of the hologram optical element 8 in the 0th order light from the diffractive optical element 3.
It is the first-order diffracted light and corresponds to the + 1st-order diffracted light from the region 20, and is condensed on the boundary line between the light receiving portions 23 and 24.

The light spot L45 is the + from the region 16 of the hologram optical element 8 in the 0th order light from the diffractive optical element 3.
It is the first-order diffracted light and corresponds to the + 1st-order diffracted light from the region 17, and is condensed on the boundary line between the light receiving portions 25 and 26.

The light spot L46 is the + from the region 16 of the hologram optical element 8 in the 0th order light from the diffractive optical element 3.
The 1st-order diffracted light corresponds to the + 1st-order diffracted light from the region 18, and is condensed on the boundary line between the light receiving portions 25 and 26.

The light spot L47 is the + from the region 16 of the hologram optical element 8 in the 0th order light from the diffractive optical element 3.
The 1st-order diffracted light corresponds to the + 1st-order diffracted light from the region 19 and is condensed on the boundary line between the light receiving units 27 and 28.

The light spot L48 is + from the region 16 of the hologram optical element 8 in the 0th order light from the diffractive optical element 3.
It is the first-order diffracted light and corresponds to the + 1st-order diffracted light from the region 20, and is condensed on the boundary line between the light receiving portions 27 and 28.

Of the light receiving parts of the photodetector 11, the light receiving parts 29 to
Reference numeral 34 denotes a light receiving portion for the sub beam which is the + 1st order diffracted light by the diffractive optical element 3, light receiving portions 29 to 31 are light receiving portions for the + 1st order diffracted light by the area 15 of the hologram optical element 8, and light receiving portions 32 to 34 are the areas. It is a light receiving portion for + 1st order diffracted light by 16. Light receiving parts 29 to 31 and light receiving parts 32 to 34
Are formed by dividing both ends in the radial direction of the rectangular light receiving portion along the radial direction R by two dividing lines along the tangential direction T, respectively.

That is, the light receiving portion 30 receives the center portion of the + 1st order diffracted light divided by the region 15 in the radial direction, and the light receiving portions 29 and 31 individually receive both end portions in the radial direction. In addition, the light receiving unit 33 has the area 16
The + 1st-order diffracted light split by is further received in the central portion in the radial direction, and the respective light receiving portions 32 and 34 individually receive both end portions in the radial direction.

On the other hand, the light spot L49 is the diffractive optical element 3
Out of the + 1st order diffracted light from the area 15 of the hologram optical element 8 corresponding to the + 1st order diffracted light from the area 17, and is condensed on the light receiving section 29.

The light spot L50 is the + 1st-order diffracted light from the area 15 of the hologram optical element 8 and the + 1st-order diffracted light from the area 18 of the + 1st-order diffracted light from the diffractive optical element 3, and is collected on the light receiving section 30. Be illuminated.

The light spot L51 is the + 1st order diffracted light from the area 15 of the hologram optical element 8 out of the + 1st order diffracted light from the diffractive optical element 3 and corresponds to the + 1st order diffracted light from the area 19, and is collected on the light receiving section 30. Be illuminated.

The light spot L52 is the + 1st-order diffracted light from the region 15 of the hologram optical element 8 out of the + 1st-order diffracted light from the diffractive optical element 3 and corresponds to the + 1st-order diffracted light from the region 20, and is collected on the light receiving section 31. Be illuminated.

The light spot L53 is the + 1st order diffracted light from the area 16 of the hologram optical element 8 out of the + 1st order diffracted light from the diffractive optical element 3 and corresponds to the + 1st order diffracted light from the area 17, and is collected on the light receiving section 32. Be illuminated.

The light spot L 54 corresponds to the + 1st-order diffracted light from the area 16 of the hologram optical element 8 and the + 1st-order diffracted light from the area 18 of the + 1st-order diffracted light from the diffractive optical element 3, and is collected on the light receiving section 33. Be illuminated.

The light spot L55 is the + 1st-order diffracted light from the region 16 of the hologram optical element 8 out of the + 1st-order diffracted light from the diffractive optical element 3 and corresponds to the + 1st-order diffracted light from the region 19, and is collected on the light receiving portion 33. Be illuminated.

The light spot L56 is the + 1st-order diffracted light from the region 16 of the hologram optical element 8 and the + 1st-order diffracted light from the region 20 among the + 1st-order diffracted light from the diffractive optical element 3, and is collected on the light receiving section 34. Be illuminated.

Among the light receiving portions of the photodetector 11, the light receiving portions 35 to 35
Reference numeral 40 denotes a light receiving portion for the sub beam which is the −1st order diffracted light by the diffractive optical element 3, light receiving portions 35 to 37 are light receiving portions for the + 1st order diffracted light by the region 15 of the hologram optical element 8, and light receiving portions 38 to 40 are It is a light receiving portion for the + 1st order diffracted light by the region 16. Light receiving parts 35 to 37 and light receiving parts 38 to 40
Are formed by dividing both ends in the radial direction of the rectangular light receiving portion along the radial direction R by two dividing lines along the tangential direction T, respectively.

That is, the light receiving section 36 further receives the central portion in the radial direction of the -1st order diffracted light divided by the area 15, and the respective light receiving sections 35 and 37 individually receive both end portions in the radial direction. In addition, the light receiving unit 39 has the area 16
The -1st-order diffracted light divided by is further received in the central portion in the radial direction, and the respective light receiving portions 38 and 40 individually receive both end portions in the radial direction.

On the other hand, the light spot L57 is the diffractive optical element 3
Out of the −1st order diffracted light from the region 15 of the hologram optical element 8 corresponding to the + 1st order diffracted light from the region 17, and is condensed on the light receiving unit 35.

The light spot L58 corresponds to the + 1st-order diffracted light from the region 15 of the hologram optical element 8 and the + 1st-order diffracted light from the region 18 of the −1st-order diffracted light from the diffractive optical element 3 and corresponds to the light-receiving portion 36. Collected.

The light spot L59 is the + 1st-order diffracted light from the region 15 of the hologram optical element 8 and the + 1st-order diffracted light from the region 19 of the −1st-order diffracted light from the diffractive optical element 3, and corresponds to the + 1st-order diffracted light on the light receiving portion 36. Collected.

The light spot L60 is the + 1st order diffracted light from the area 15 of the hologram optical element 8 and the + 1st order diffracted light from the area 20 of the −1st order diffracted light from the diffractive optical element 3 and corresponds to the light receiving portion 37. Collected.

The light spot L61 corresponds to the + 1st-order diffracted light from the area 16 of the hologram optical element 8 and the + 1st-order diffracted light from the area 17 of the −1st-order diffracted light from the diffractive optical element 3 and corresponds to the light-receiving portion 38. Collected.

The light spot L62 corresponds to the + 1st-order diffracted light from the area 16 of the hologram optical element 8 and the + 1st-order diffracted light from the area 18 of the −1st-order diffracted light from the diffractive optical element 3, and is on the light receiving portion 39. Collected.

The light spot L63 is the + 1st-order diffracted light from the region 16 of the hologram optical element 8 and the + 1st-order diffracted light from the region 19 among the −1st-order diffracted light from the diffractive optical element 3 and corresponds to the light receiving portion 39. Collected.

The light spot L 64 is the + 1st-order diffracted light from the area 16 of the hologram optical element 8 and the + 1st-order diffracted light from the area 20 of the −1st-order diffracted light from the diffractive optical element 3, and corresponds to the + 1st-order diffracted light on the light receiving section 40. Collected.

Next, the signal processing circuit 201 will be described. Each of the light receiving units 21 to 40 of the photodetector 11 outputs a current according to the intensity of the received light. Each light receiving unit 21 to
If the outputs from 40 are represented by V21 to V40, respectively,
The signal processing circuit 201 uses the Foucault method to convert the focus error signal into (V21 + V23 + V26 + V28) − (V
22 + V24 + V25 + V27) and outputs it to the operation control means 200. In addition, the signal processing circuit 20
1 is a track error signal (V
21 + V22 + V25 + V26)-(V23 + V24 +
V27 + V28), and the operation control means 20
Output to 0. Further, the signal processing circuit 201 outputs the reproduction signal to V21 + V22 + V23 + V24 + V25 + V2.
It is calculated from the calculation of 6 + V27 + V28 and is output to, for example, a host device to which the optical information recording / reproducing device 1 is connected.

Further, the signal processing circuit 201 outputs from the diffractive optical element 3 on the disc D1 based on the output of each of the light receiving parts 29 to 40 of the ± first-order diffracted light (sub-beams) from the diffractive optical element 3 in the photodetector 11. The discriminant signal generator 203 for generating a discriminating signal indicating whether the focused spot L12 of the 0th-order light (main beam) is located on the land or the groove.

The land / groove discrimination signal is (V29
+ V31 + V32 + V34)-(V30 + V33),
(V35 + V37 + V38 + V40)-(V36 + V3
9) or (V29 + V31 + V32 + V34 + V36
+ V39)-(V30 + V33 + V35 + V37 + V3
8 + V40), but in the present embodiment, the discrimination signal generation unit 203
(V29 + V31 + V32 + V34 + V36 + V39)
-(V30 + V33 + V35 + V37 + V38 + V4
The land / groove discrimination signal is calculated from the calculation of 0).

The reason why the land / groove discrimination signal is obtained from the above equations will be described below with reference to FIGS. 6 to 12. FIG. 6 shows the positional relationship of the 0th-order light and the ± 1st-order diffracted light from the disc D1 with respect to the focused spot L12 on the disc D1, and FIG. 7 shows the focused spot L12 and the track D2.
3 shows changes in the phases of the 0th-order light and the ± 1st-order diffracted lights from the disk D1 due to the position shift of. The focused spot L12 is formed by the light beam L65 and is focused on the disc D1. Therefore, the wavefront (equal phase surface) of the 0th-order light and the ± 1st-order diffracted light is a flat surface.

In FIG. 7A, the light beam L65 is applied to the groove D3. At this time, as shown in FIG. 7B, when the phase of the 0th-order light is 0, the phases of the ± 1st-order diffracted lights are both −π / 2. In FIG. 7C, the light beam L65 is applied to the boundary between the groove D3 and the land D4. At this time, as shown in FIG.
The phase of the + 1st order diffracted light is delayed by π / 2 with respect to the state of (B),
The phase of the −1st order diffracted light advances by π / 2. Therefore, when the phase of the 0th order light is 0, the phase of the + 1st order diffracted light is π or −π, −
The phase of the first-order diffracted light becomes zero.

In FIG. 7E, the light beam L65 is applied to the land D4. At this time, as shown in FIG. 7F, the phase of the + 1st-order diffracted light is delayed by π / 2 and the phase of the −1st-order diffracted light is advanced by π / 2 with respect to the state of FIG. 7D. Therefore, when the phase of the 0th order light is 0, the phases of the ± 1st order diffracted lights are both π / 2. In FIG. 7G, the light beam L65 is applied to the boundary between the land D4 and the groove D3.
At this time, as shown in FIG. 7 (H), the phase of the + 1st-order diffracted light is delayed by π / 2 and the phase of the −1st-order diffracted light is advanced by π / 2 with respect to the state of FIG. 7 (F). Therefore, if the phase of the 0th-order light is 0, the phase of the + 1st-order diffracted light is 0, and the phase of the -1st-order diffracted light is π.
Alternatively, it becomes −π.

As described above, with the movement of the light beam L65, the intensities in the region L68 where the 0th order light and the + 1st order diffracted light overlap and the region L69 where the 0th order light and the −1st order diffracted light overlap (see FIG. 6) are as follows. become.

In the state of FIG. 7A, as shown in FIG. 7B, since the phase difference between the 0th order light and the ± 1st order diffracted lights is π / 2, the intensities in the regions L68 and L69 are equal. . In the state of FIG. 7C, as shown in FIG.
Since the phase difference between the second-order light and the + 1st-order diffracted light is π, they weaken each other by interference, and the phase difference between the 0th-order light and the -1st-order diffracted light is 0, which strengthen each other by interference. Therefore, the intensity in the region L68 is weaker than that in the region L69. .

In the state of FIG. 7 (E), as shown in FIG. 7 (F), the phase difference between the 0th order light and the ± 1st order diffracted lights is π / 2, so that the intensities in the regions L68 and L69 are equal. . In the state of FIG. 7 (G), as shown in FIG. 7 (H), 0
Since the phase difference between the second-order light and the + 1st-order diffracted light is 0, they strengthen each other by interference, and the phase difference between the 0th-order light and the -1st-order diffracted light weakens each other by π, so the intensity in the region L68 is stronger than that in the region L69. .

FIG. 8 shows a focused spot L1 on the disc D1.
3 shows the positional relationship between the 0th-order light and the ± 1st-order diffracted light from the disk D1 with respect to No. 3, and FIG.
The change in the phase of the second-order diffracted light is shown. The focused spot L13 is formed by the light beam L70, is slightly defocused on the disk D1, and is located in front of the focused point when viewed from the incident side. For this reason, the wavefronts (equal phase surfaces) of the 0th-order light and the ± 1st-order diffracted lights are downwardly convex paraboloids, and the phases of the 0th-order light and the ± 1st-order diffracted lights are advanced in the peripheral portion compared to the central portion.

In FIG. 9A, the light beam L70 is irradiated onto the groove D3. At this time, as shown in FIG. 9B, when the phase of the central part of the 0th-order light is 0, the phases of the central part of the ± 1st-order diffracted lights are both −π / 2. Figure 9
In (C), the light beam L70 is reflected by the groove D3 and the land D.
It is illuminated on the border of 4. At this time, as shown in FIG. 9D, the phase of the + 1st-order diffracted light is delayed by π / 2 and the phase of the −1st-order diffracted light is advanced by π / 2 with respect to the state of FIG. 9B. Therefore, when the phase of the central part of the 0th order light is 0, the phase of the central part of the + 1st order diffracted light is π or −π, and the phase of the central part of the −1st order diffracted light is 0.

In FIG. 9E, the light beam L70 is applied to the land D4. At this time, as shown in FIG. 9F, the phase of the + 1st-order diffracted light is delayed by π / 2 and the phase of the −1st-order diffracted light is advanced by π / 2 with respect to the state of FIG. 9D. Therefore, if the phase of the central part of the 0th order light is 0, the phases of the central part of the ± 1st order diffracted lights are both π / 2. In FIG. 9 (G),
The light beam L70 is irradiated onto the boundary between the land D4 and the groove D3. At this time, as shown in FIG.
The phase of the + 1st-order diffracted light is delayed by π / 2 and the phase of the −1st-order diffracted light is advanced by π / 2 with respect to the state of FIG. 9 (F). Therefore, when the phase of the central part of the 0th order light is 0, the phase of the central part of the + 1st order diffracted light is 0, and the phase of the central part of the −1st order diffracted light is π or −π.

As described above, with the movement of the light beam L70, the outer region L71 where the 0th-order light and the + 1st-order diffracted light overlap,
The intensities in the inner region L72, the inner region L73 where the 0th-order light and the −1st-order diffracted light overlap, and the outer region L74 are as follows.

In the state of FIG. 9A, as shown in FIG. 9B, the phase difference between the 0th-order light and the ± 1st-order diffracted lights is π outside.
/ 2, which are slightly weaker due to interference, and both are slightly smaller than π / 2, so that they are mutually strengthened due to interference. Therefore, the strength in the regions L71 and L74 is the regions L72 and L74.
It is slightly weaker than the strength at 73.

In the state of FIG. 9C, as shown in FIG. 9D, the phase difference between the 0th-order light and the + 1st-order diffracted light is slightly smaller than π on the outside and also slightly smaller than π on the inside. And the region L72 have substantially the same intensity, and the phase difference between the 0th-order light and the −1st-order diffracted light is slightly larger than 0 on the outside and also slightly larger than 0 on the inside, so that the region L73
And the intensities in the region L74 are almost equal.

In the state of FIG. 9E, as shown in FIG. 9F, the phase difference between the 0th-order light and the ± 1st-order diffracted lights is π outside.
The strength in the regions L71, L74 is slightly smaller than / 2 and slightly strengthens each other due to the interference, and both of them are slightly weaker than each other due to the interference slightly larger than π / 2.
A little stronger than the strength at 73.

In the state of FIG. 9G, as shown in FIG. 9H, the phase difference between the 0th-order light and the + 1st-order diffracted light is slightly larger than 0 on the outer side and slightly larger than 0 on the inner side. And the intensity in the region L72 are almost equal, and the phase difference between the 0th-order light and the −1st-order diffracted light is slightly smaller than π on the outer side and slightly smaller than π on the inner side.
And the intensities in the region L74 are almost equal.

FIG. 10 shows a focused spot L on the disc D1.
14 shows the positional relationship between the 0th-order light and the ± 1st-order diffracted lights from the disk D1 with respect to No. 14, and FIG.
The change in the phase of the ± first-order diffracted light is shown. Focused spot L14
Is formed by the light beam L75, is slightly defocused on the disk D1, and is located farther than the condensing point when viewed from the incident side. Therefore, the wavefronts (equal phase surfaces) of the 0th-order light and the ± 1st-order diffracted lights are paraboloids that are convex upward, and
The phase of the peripheral portion of the first-order diffracted light lags behind that of the central portion.

In FIG. 11A, the light beam L75 is applied to the groove D3. At this time, FIG. 11 (B)
As shown in, when the phase of the central part of the 0th order light is 0, ±
The phases of the central part of the first-order diffracted light are both -π / 2. Figure 1
In 1 (C), the light beam L75 is applied to the boundary between the groove D3 and the land D4. At this time, FIG.
As shown in FIG. 11D, the phase of the + 1st-order diffracted light is delayed by π / 2 with respect to the state of FIG.
Go 2 Therefore, if the phase of the central part of the 0th order light is 0,
The phase of the central part of the + 1st order diffracted light is π or −π, and the phase of the central part of the −1st order diffracted light is 0.

In FIG. 11E, the light beam L75 is applied to the land D4. At this time, as shown in FIG. 11F, the phase of the + 1st-order diffracted light is delayed by π / 2 and the phase of the −1st-order diffracted light is advanced by π / 2 with respect to the state of FIG. 11D.
Therefore, if the phase of the central part of the 0th order light is 0, the phases of the central part of the ± 1st order diffracted lights are both π / 2. FIG. 11 (G)
In, the light beam L75 is applied to the boundary between the land D4 and the groove D3. At this time, as shown in FIG. 11 (H), the phase of the + 1st-order diffracted light is delayed by π / 2 and the phase of the −1st-order diffracted light is advanced by π / 2 with respect to the state of FIG. 11 (F). Therefore, if the phase of the central part of the 0th-order light is 0, the phase of the central part of the + 1st-order diffracted light is 0, and the phase of the central part of the -1st-order diffracted light is π.
Alternatively, it becomes −π.

As described above, with the movement of the light beam L75, the outer region L76 where the 0th-order light and the + 1st-order diffracted light overlap,
The intensities in the inner region L77, the inner region L78 where the 0th-order light and the −1st-order diffracted light overlap and the outer region L79 are as follows. In the state of FIG. 11 (A), as shown in FIG. 11 (B), the phase difference between the 0th order light and the ± 1st order diffracted light is slightly smaller than π / 2 on the outside and slightly strengthened by interference, and both on the inside are π /. 2, the strengths in the regions L76 and L79 are slightly weakened by the interference due to the interference.
It is slightly stronger than the strength of L78. In the state of FIG. 11C, as shown in FIG. 11D, the phase difference between the 0th-order light and the + 1st-order diffracted light is slightly smaller than π on the outside and also slightly smaller than π on the inside, so that the regions L76 and L77. Since the intensities are substantially equal to each other and the phase difference between the 0th-order light and the −1st-order diffracted light is slightly larger than 0 on the outside and also slightly larger than 0 on the inside, the intensities in the regions L78 and L79 are almost equal.

In the state of FIG. 11 (E), as shown in FIG. 11 (F), the phase difference between the 0th-order light and the ± 1st-order diffracted light is slightly larger than π / 2 on the outer side and slightly weakened by the interference, and on the inner side. Since both are slightly smaller than π / 2 and strengthen each other by interference, the strength in the regions L76 and L79 is the region L77,
It is slightly weaker than the strength at L78. In the state of FIG. 11G, as shown in FIG. 11H, the phase difference between the 0th-order light and the + 1st-order diffracted light is slightly larger than 0 on the outer side and slightly larger than 0 on the inner side. Since the intensities are substantially equal to each other and the phase difference between the 0th-order light and the -1st-order diffracted light is slightly smaller than π on the outside and also slightly smaller than π on the inside, the intensities in the regions L78 and L79 are almost equal.

FIG. 12 shows various waveforms related to the track error signal and the land / groove discrimination signal. The horizontal axis represents the positional deviation between the focused spots L12 to L14 when the focused spots L12 to L14 traverse the groove of the disk D1 from the left side to the right side in FIG.
L14 is located on the groove, b is the focused spots L12 to L14 located on the boundary between the groove and the land, and c is the focused spot L12 to L14 located on the land. , D are focused spots L12 to L
14 corresponds to the state of being located on the boundary between the land and the groove. That is, a to d are shown in FIGS.
11 corresponds to the states (A) to (D).

Due to the hologram optical element 8 described above, the area L68 in FIG.
The light is received by 2, 25, and 26, and the area L69 is the photodetector 11.
The light is received by the light receiving units 23, 24, 27, and 28 of. At this time, (V21 + V22 + V25 + V26)-(V23 +
The value of (V24 + V27 + V28) is 0 according to FIG. 7B, is negative according to FIG. 7D, is 0 according to FIG. 7F, and is positive according to FIG. The signal is (V21 + V22 + V25 + V26)-(V23 + V
The waveform of 24 + V27 + V28) is as shown in FIG.

By the hologram optical element 8 described above, the area L71 in FIG.
The area L72 and the area L73 are received by the light receiving sections 30 and 33 of the photodetector 11, and the area L74 is received by the light receiving sections 31 and 34 of the photodetector 11. At this time,
(V29 + V31 + V32 + V34)-(V30 + V3
The value of 3) is negative according to FIG. 9 (B), almost 0 according to FIG. 9 (D), positive according to FIG. 9 (F), and almost 0 according to FIG. 9 (H). First land / groove discrimination signal (V29 + V31 + V32 + V34)-(V30 +
The waveform of V33) is as shown in FIG.

Due to the hologram optical element 8 described above, the area L76 in FIG.
38, regions L77 and L78 are the light receiving parts 36 and 39 of the photodetector 11, and region L79 is the light receiving part 3 of the photodetector 11.
It corresponds to 7 and 40 respectively. At this time, (V35
The value of + V37 + V38 + V40)-(V36 + V39) is positive according to FIG. 11 (B), almost 0 according to FIG. 11 (D), negative according to FIG. 11 (F), and almost 0 according to FIG. 11 (H). Therefore, the second land / groove discrimination signal is (V35 + V37 + V38 + V40) − (V36 +
The waveform of V39) is as shown in FIG.

Since the waveforms of FIGS. 12B and 12C have opposite phases, they are the difference between the first and second land / groove discrimination signals, that is, the third land / groove discrimination signal. (V29 + V31 + V32 + V34 + V36 + V3
9)-(V30 + V33 + V35 + V37 + V38 + V
The waveform of 40) is as shown in FIG.

The focused spots L12 to L14 are the disk D.
12 (A) when it is located on the groove 1 of FIG.
The track error signal shown in FIG.
The first to third land / groove discrimination signals shown in FIG. 12D have negative, positive, and negative values, respectively. On the other hand, in the state where the focused spots L12 to L14 are located on the land of the disc D1, the track error signal shown in FIG. 12 (A) is 0, but the track error signals shown in FIG. 12 (B) to FIG. 12 (D). The first to third land / groove discrimination signals shown are positive,
Takes negative and positive values. Therefore, it is possible to detect which of the land and the groove of the disc D1 the focused spots L12 to L14 are located on by the sign of the land / groove discrimination signal.

The light receiving portions 30 and 33 of the photodetector 11 have the disc D1 other than the regions L72 and L73 in FIG.
From the disk D1
Since the area of only the ± 1st-order diffracted light from is outside the range of the effective diameter of the objective lens 6, the light receiving portions 29 and 32 of the photodetector 11 are
8 includes only the region L71 in FIG. 8, and the light receiving portions 31 and 34 of the photodetector 11 include only the region L74 in FIG.

Therefore, the first land / groove discrimination signal shown in FIG. 12B has a negative DC component, and the absolute value of the signal at the land becomes smaller than the absolute value of the signal at the groove. The margin for position detection on the land is narrower than the margin for position detection on the groove.

Further, the light receiving portions 36 and 39 of the photodetector 11 include not only the regions L77 and L78 in FIG. 10 but also the region of only the 0th order light from the disc D1, but the ± 1st order diffracted light from the disc D1. The only area is the objective lens 6
Is outside the range of the effective diameter of the light detector 3 of the photodetector 11.
Reference numerals 5 and 38 include only the area L76 in FIG. 10, and the light receiving portions 37 and 40 of the photodetector 11 include only the area L79 in FIG.

Therefore, the second land / groove discrimination signal shown in FIG. 12C has a negative DC component, and the absolute value of the signal in the groove becomes smaller than the absolute value of the signal in the land. The margin for position detection in the groove is narrower than the margin for position detection in the land.

On the other hand, the third land / groove discrimination signal shown in FIG. 12D does not have a DC component because the DC components of the first and second land / groove discrimination signals cancel each other out. In addition, a sufficient margin for position detection can be obtained in both the land and the groove.

Next, the operation control means 200 will be described. In this operation control means 200, the head drive means is driven according to the value of the focus error signal or the track error signal output from the signal processing circuit 201 described above, and focusing and tracking are performed.

Further, the operation control means 200 has a track servo circuit (not shown), and this track servo circuit controls the operation of the head drive means so that the focused spot L12 follows a desired track of the disk D1. .

Further, the operation control means 200 uses the disk D
When the track 1 is accessed, the judgment advance function 20 for performing the track servo pull-in operation after receiving the land / groove judgment signal from the signal processing circuit 20
Have four. Therefore, it is known in advance whether the focused spot is located on the land or on the groove, so that the track servo pull-in operation can be stably performed, and the track servo runaway can be effectively avoided. Is possible.

As described above, the optical information recording / reproducing apparatus 1
Then, when the focused spot L12 of the 0th-order light is focused on the disk D1, the focused spot L13 of the ± 1st-order diffracted light,
Since the diffractive optical element 3 for defocusing L14 on the disc D1 is provided, the focused spot L13 of the ± 1st-order diffracted light depends on whether the focused spots L12 to L14 are located on the land or the groove. A phase difference between the 0th-order light and the ± 1st-order diffracted light from the disc D1 can be produced in the central portion and both end portions of the reflected light of L14, and accordingly, a difference in light intensity is produced between them. It is possible.

On the other hand, according to the present invention, since the photodetector is provided with the light receiving portions for individually receiving the reflected light of the sub-beam at the central portion and both end portions in the radial direction, the central portion and the both end portions of the reflected light of the sub-beam are provided. It is possible to observe the difference in light intensity between the part and the part, and based on this, it is possible to determine whether the focused spot of the sub beam is on the land or on the groove. Also, by setting the relative positional relationship between the sub beam and the main beam in advance, it is possible to obtain a determination signal for determining whether the focused spot of the main beam is on the land or the groove from the determination of the sub beam. Is possible.

On the other hand, in the optical information recording / reproducing apparatus 1, the photodetector 11 is provided with the light receiving portions for individually receiving the reflected light of the ± 1st-order diffracted light from the diffractive optical element 3 at the center and both ends in the radial direction. Since it has, it is possible to observe the difference in the light intensity between the central portion and both end portions of the reflected light of the ± 1st-order diffracted light, and based on this, each focused spot L12 ...
It is possible to determine whether L14 is on the land or on the groove.

In the light source section 202, the diffractive optical element 3
Has its orientation set so that the respective focused spots L12 to L14 are aligned on the same track D2 of the disk D1, so that the positional relationship between the main beam and the sub beam is set according to the track pitch as in the conventional case. No need to
It is possible to identify the land / groove for various optical recording media having different track pitches.

Further, since the above-mentioned judgment can be realized by the diffractive optical element 3 in which the incident surface is composed of a single area, the lens power is very weak, and the grating pattern is close to straight lines at substantially equal intervals, Such a diffractive optical element divided into a plurality of regions is not essential, and therefore the position of the optical element can be easily adjusted.

In the optical information recording / reproducing apparatus 1 described above, the photodetector 11 has a light receiving section for receiving both the ± first-order diffracted light from the diffractive optical element 3, and the signal processing circuit 201 detects both of them. The discrimination signal is generated from the result, but the present invention is not limited to this. For example,
The photodetector has only a light receiving part for receiving one of the ± first-order diffracted lights from the diffractive optical element 3 (for example, the photodetector 11 without the light receiving parts 35 to 40), and in the signal processing circuit ( V29 + V31 + V32 + V34)-(V3
0 + V33) may be used to generate the discrimination signal. In this case, although the margin of the land or groove becomes low, it is possible to sufficiently generate the discrimination signal.

(Second Embodiment) Next, the second embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 13 and 14. It should be noted that, of the components shown in the present embodiment, the same components as those of the optical information recording / reproducing apparatus 1 described above are designated by the same reference numerals, and a duplicate description will be omitted.

FIG. 13 shows a block diagram of an optical information recording / reproducing apparatus 1A according to the second embodiment. In this optical information recording / reproducing apparatus 1A, a cylindrical lens 80 is provided at the same position in place of the hologram optical element 8 described above, and the photodetector 11
In place of the photodetector 81 having a small number of light receiving parts, and further has various optical signals generated based on the output of the photodetector 81 in place of the signal processing circuit 201. The optical information recording / reproducing apparatus 1 is different from the optical information recording / reproducing apparatus 1 in that it has a signal processing circuit 201A for performing the same. Therefore, the arrangement of the focused spot on the disc D1 by the light emitted from the light source unit 202 is the same as that of the optical information recording / reproducing apparatus 1 (see FIG. 3).

The two focal lines of the cylindrical lens 80 and the lens 9 are set at different positions in the direction along the optical axis, and the photodetector 81 is installed between the two focal lines. .

FIG. 14 shows the pattern of the light receiving portion of the photodetector 81 and the arrangement of the light spots on the photodetector 81. The photodetector 81 includes a dividing line parallel to the radial direction of the disc D1 passing through the optical axis on the light receiving surface for receiving the 0th order light from the diffractive optical element 3 and a dividing line parallel to the tangential direction intersecting the dividing line. Four light receiving parts 82, 8 separated by and
3, 84, 85 and three light receiving portions 86, 8 formed by partitioning the light receiving surface for receiving the + 1st order diffracted light with two dividing lines parallel to the tangential direction of the disk D1 passing through the optical axis.
7, 88 and three light receiving portions 89, 90, 91 formed by partitioning the light receiving surface for receiving the −1st order diffracted light with two dividing lines parallel to the tangential direction of the disk D1 passing through the optical axis.
It has and.

The light spot L92 corresponds to the 0th order light from the diffractive optical element 3 and is received by each of the light receiving sections 82 to 85. The light spot L93 corresponds to the + 1st order diffracted light from the diffractive optical element 3 and is received by the light receiving units 86 to 88. Light spot L
Reference numeral 94 corresponds to the −1st order diffracted light from the diffractive optical element 3 and is received by the light receiving units 89 to 91. Three light spots L9
The light spots L92, L93, and L94 are arranged in a line in the same direction as the condensing spots L12, L13, and L14 on the disc D1.
By the action of the cylindrical lens 80 and the lens 9 individually.
The light is received by the photodetector 81 in a state of being rotated by 0 degree. Therefore, as described above, the ± first-order diffracted light has a light-receiving surface which is parallel to the tangential direction of the disc D1 passing through the optical axis.
The light is received by the three light receiving sections that are separated by one dividing line. Therefore, the ± first-order diffracted light is individually received at the central portion and both end portions in the radial direction.

Next, the signal processing circuit 201A will be described. Each of the light receiving units 82 to 91 of the photodetector 81 outputs a current corresponding to the intensity of the received light. Each light receiving unit 82
When the outputs from ˜91 are represented by V82 to V91, respectively, the signal processing circuit 201A calculates the focus error signal by (V82 + V85) − (V83 + V8) by the astigmatism method.
It is calculated from the calculation of 4) and output to the operation control means 200. Further, the signal processing circuit 201A uses the push-pull method to calculate the track error signal by (V82 + V84)-(V8
3 + V85) and outputs it to the operation control means 200. Further, the signal processing circuit 201A calculates a reproduction signal from the calculation of V82 + V83 + V84 + V85, and outputs it to, for example, a host device to which the optical information recording / reproducing device 1A is connected.

Further, the signal processing circuit 201A causes the diffractive optical element 3 on the disc D1 to output from the diffractive optical element 3 in the photodetector 81 based on the outputs of the respective light receiving portions 86 to 91 of the ± first-order diffracted light (sub beams). The discriminant signal generation unit 203A that generates a discriminant signal indicating whether the focused spot L12 of the 0th-order light (main beam) is located on the land or the groove.

The land / groove discrimination signal is (V86
+ V88) -V87, (V89 + V91) -V90, or (V86 + V88 + V90)-(V87 + V89 + V
Although it can be calculated from any of the calculation of 91),
In the present embodiment, the determination signal generation unit 203A uses (V86
The land / groove discrimination signal is calculated from the calculation of + V88 + V90)-(V87 + V89 + V91).

The disk D described in FIGS. 6 to 11 above.
The relationship between the positional deviation between the focused spots L12 to L14 on the first track and the track D2 and the change in the phase of the 0th-order light and the ± 1st-order diffracted light from the disc D1 that accompanies this is as follows.
The same applies to 94.

That is, the area L68 in FIG. 6 is received by the light receiving portions 82 and 84 of the photodetector 81, and the area L69 is received by the light receiving portions 83 and 85 of the photodetector 81. At this time,
The value of (V82 + V84)-(V83 + V85) is shown in FIG.
0 in (A), negative in FIG. 7 (C), 0 in FIG. 7 (E),
Since it is positive in FIG. 7G, the waveform of the track error signal (V82 + V84) − (V83 + V85) is shown in FIG.
It becomes like 2 (A).

The area L71 in FIG. 8 is received by the light receiving section 86 of the photodetector 81, the areas L72 and L73 are received by the light receiving section 87 of the photodetector 81, and the area L74 is received by the light receiving section 88 of the photodetector 81. Is received by. At this time, (V
The value of (86 + V88) -V87 is negative in FIG.
Since it is almost 0 in (C), positive in FIG. 9 (E), and almost 0 in FIG. 9 (G), the waveform of (V86 + V88) −V87 which is the first land / groove discrimination signal is shown in FIG.
It becomes like (B).

A region L76 in FIG. 10 is a photodetector 81.
The light is received by the light receiving portion 89 of the area L77 and the area L78.
Is received by the light receiving section 90 of the photodetector 81, and the region L79 is received by the light receiving section 91 of the photodetector 81. At this time,
The value of (V89 + V91) -V90 is positive in FIG. 11 (A), almost 0 in FIG. 11 (C), negative in FIG. 11 (E), and almost 0 in FIG. 11 (G). The waveform of the groove discrimination signal (V89 + V91) -V90 is as shown in FIG. 12 (C). 12 (B) and FIG.
Since the waveform of (C) is in opposite phase, the first and second lands /
The difference between the groove discrimination signals, that is, the third land / groove discrimination signal (V86 + V88 + V90)-
The waveform of (V87 + V89 + V91) is as shown in FIG.

The focused spots L12 to L14 are the disk D.
12 (A) when it is located on the groove 1 of FIG.
The track error signal shown in FIG.
The first to third land / groove discrimination signals shown in FIG. 12D have negative, positive, and negative values, respectively. On the other hand, in the state where the focused spots L12 to L14 are located on the land of the disc D1, the track error signal shown in FIG. 12 (A) is 0, but the track error signals shown in FIG. 12 (B) to FIG. 12 (D). The first to third land / groove discrimination signals shown are positive,
Takes negative and positive values. Therefore, it is possible to detect which of the land and the groove of the disc D1 the focused spots L12 to L14 are located on by the sign of the land / groove discrimination signal.

The light-receiving portion 87 of the photodetector 81 includes not only the regions L72 and L73 in FIG. 8 but also the region of 0th-order light from the disc D1, but the region of only ± 1st-order diffracted light from the disc D1. Since it is outside the range of the effective diameter of the objective lens 6, the light receiving portion 86 of the photodetector 81 includes only the area L71 in FIG. 8, and the light receiving portion 88 of the photodetector 81 includes only the area L74 in FIG. I'm out. Therefore, the first land / groove discrimination signal shown in FIG. 12B has a negative DC component, and the absolute value of the signal at the land becomes smaller than the absolute value of the signal at the groove, and the position at the land The detection margin is narrower than the position detection margin in the groove.

The light receiving portion 90 of the photodetector 81 is shown in FIG.
In addition to the areas L77 and L78 in FIG.
The disc D includes the area of 0th-order light from 1
Since the area of only the ± 1st-order diffracted light from 1 is outside the range of the effective diameter of the objective lens 6, the light receiving portion 89 of the photodetector 81 includes only the area L76 in FIG.
The light receiving unit 91 of No. 1 includes only the region L79 in FIG. Therefore, the second land / shown in FIG.
The groove discrimination signal has a negative DC component, the absolute value of the signal in the groove becomes smaller than the absolute value of the signal in the land, and the margin for position detection in the groove becomes narrower than the margin for position detection in the land. .

On the other hand, the third land / groove discrimination signal shown in FIG. 12D has no DC component because the DC components of the first and second land / groove discrimination signals cancel each other out. In addition, a sufficient margin for position detection can be obtained in both the land and the groove.

In the second embodiment, the optical element for slightly defocusing the focused spot of the sub-beam on the disc in the radial direction is shown in FIG.
The diffractive optical element 3 shown in is used. The diffractive optical element 3 is composed of a single region, the lens power is very weak, and the grating pattern can be regarded as straight lines at substantially equal intervals, so that in-plane position adjustment is unnecessary.

As described above, the optical information recording / reproducing apparatus 1
A can achieve the same effect as the optical information recording / reproducing apparatus 1 described above.

(Third Embodiment) Next, the third embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 15 and 16. It should be noted that, of the components shown in the present embodiment, the same components as those of the optical information recording / reproducing apparatus 1 described above are designated by the same reference numerals, and a duplicate description will be omitted. FIG. 15 shows a block diagram of the optical information recording / reproducing apparatus 1B according to the present embodiment.

The optical information recording / reproducing apparatus 1B includes an optical head device 10B, a head driving means (not shown) for focusing and tracking via the optical head device 10B, and an operation control means 20 for the head driving means.
0 and a signal processing circuit 201.

The optical head device 10B includes a light source section 202B for emitting a main beam and a sub beam. The light source unit 202B includes a semiconductor laser 96 as a light source that emits a single laser beam, and the semiconductor laser 9
The collimator lens 2 for collimating the emitted light of No. 6 into parallel light, and the polarizing diffractive optical element 98 for splitting the parallel light into three lights of the 0th order light which is the main beam and the ± 1st order diffracted lights which are the sub beams. ing.

Further, the optical head device 10B has a polarizing hologram optical element 99 for directly transmitting the transmitted light of the polarizing diffractive optical element 98, and the transmitted light from the polarizing hologram optical element 99 from linearly polarized light to circularly polarized light. Convert 1 /
The four wavelength plate 5 and the transmitted light of this quarter wavelength plate 5 are recorded on the disc D1.
It includes an objective lens 6 that collects light on the upper side, and a photodetector 97 that receives the reflected light from the disc D1 on a light receiving surface divided into a plurality of predetermined light receiving portions and outputs each light intensity.

In the optical head device 10B, the above-mentioned components are arranged in a line between the semiconductor laser 96 and the disk D1, and therefore the above-mentioned polarization beam splitter 4 is unnecessary. . Further, the semiconductor laser 96 and the photodetector 97 are integrally installed in the module 95.

In the above-mentioned polarizing diffractive optical element 98, the light emitted from the semiconductor laser 96 is partly diffracted as extraordinary light, and reflected light from the disk D1 which has passed through the quarter-wave plate 5 in the forward path and the backward path. Transmits almost 100% of ordinary light. In addition, the polarization hologram optical element 99 transmits almost 100% of the emitted light from the semiconductor laser 96 as ordinary light, and the reflected light from the disk D1 that has passed through the quarter-wave plate 5 in the forward and backward paths is abnormal light. Diffract most. The reflected light diffracted by the polarization hologram optical element 99 passes through the collimator lens 2 and is received by the photodetector 97.

A plan view of the polarizing diffractive optical element 98 is as follows.
It is the same as the plan view of the diffractive optical element 3 shown in FIG. Therefore, in the following description, the same reference numerals are used for the respective regions of the diffractive optical element 3. However, the polarizing diffractive optical element 98
In the region including the effective diameter of the objective lens 6 shown by the dotted line in FIG. 2, for example, a two-layer diffraction grating composed of a proton exchange region and a dielectric film is formed on a lithium niobate substrate having birefringence. It is a composition. By properly designing the depth of the proton exchange region and the thickness of the dielectric film, the phase difference between the line portion and the space portion of the lattice can be independently defined for ordinary light and extraordinary light. For abnormal light on the outward path, the phase difference between the line portion and the space portion of the grating is, for example, 0.232.
When π is set, about 87.3% of the incident light is transmitted as 0th-order light, and about 5.1% is diffracted as ± 1st-order diffracted light. On the other hand, with respect to the ordinary light on the return path, if the phase difference between the line portion and the space portion of the grating is 0, almost 100% of the incident light is transmitted as the 0th order light.

The arrangement of the focused spot on the disc D1 by the laser beam divided by the polarizing diffractive optical element 98 is as shown in FIG.
This is the same as the arrangement of 2, L13 and L14.

The plan view of the polarizing hologram optical element 99 is the same as the plan view of the hologram optical element 8 shown in FIG. Therefore, in the following description, the same reference numerals as those of the respective areas of the hologram optical element 8 are used for description. However, in the polarization hologram optical element 99, the proton is formed on the lithium niobate substrate having birefringence, for example, on both the surface on which light is incident (incident surface) and the surface on which light is emitted (emission surface). This is a configuration in which a two-layer diffraction grating including an exchange region and a dielectric film is formed. The cross-sectional shape of the grating in the diffraction grating formed on the entrance surface is a two-layer sawtooth shape in both regions 15 and 16, and the cross-sectional shape of the grating in the diffraction grating formed on the exit surface is one of regions 17 to 20. Also in 2
The layers are serrated. By properly designing the depth of the proton exchange region and the thickness of the dielectric film, the phase difference between the upper and lower portions of the sawtooth can be independently defined for ordinary light and extraordinary light. With respect to the ordinary light on the outward path, assuming that the phase difference between the upper and lower portions of the sawtooth is 0, almost 100% of the incident light to each region is transmitted as 0th-order light. On the other hand, for extraordinary light on the return path, if the phase difference between the upper and lower parts of the sawtooth is 2π,
The incident light to each area is almost 1 as + 1st order diffracted light.
00% is diffracted. The diffraction grating formed on the entrance surface and the diffraction grating formed on the exit surface of the polarization hologram optical element 99 can be replaced with each other.

Next, the photodetector 97 described above will be described in detail. FIG. 16 shows the pattern of the light receiving portion of the photodetector 97 and the arrangement of the light spots on the photodetector 97.

Of the light receiving parts of the photodetector 97, the light receiving part 101
Denoted at 108 are main beam light-receiving portions, and the light-receiving portion 101
˜104 are light receiving parts for the + 1st order diffracted light by the region 15 of the polarizing hologram optical element 99, and the light receiving parts 105 to 1
Reference numeral 08 is a light receiving portion for the + 1st order diffracted light by the region 16. Each of the light receiving units 101 to 104 and the light receiving units 105 to 108 is formed by being divided into four by a dividing line along the tangential direction T and a dividing line along the radial direction R where the rectangular light receiving units intersect with each other. There is.

On the other hand, the light spot L121 is the + 1st-order diffracted light from the region 15 of the polarizing hologram optical element 99 and the + 1st-order diffracted light from the region 17 of the 0th-order light from the polarizing diffractive optical element 98. Corresponding to the light receiving unit 101,
The light is focused on the boundary line of 102.

The light spot L122 is a polarization hologram optical element 99 of the 0th order light from the polarization diffractive optical element 98.
The + 1st-order diffracted light from the area 15 and the + 1st-order diffracted light from the area 18 are condensed on the boundary line between the light receiving portions 101 and 102.

The light spot L123 is a polarization hologram optical element 99 of the 0th order light from the polarization diffractive optical element 98.
The + 1st-order diffracted light from the area 15 and the + 1st-order diffracted light from the area 19 are condensed on the boundary line between the light receiving portions 103 and 104.

The light spot L124 is a polarization hologram optical element 99 of the 0th order light from the polarization diffractive optical element 98.
The + 1st-order diffracted light from the area 15 and the + 1st-order diffracted light from the area 20 are condensed on the boundary line between the light receiving portions 103 and 104.

The light spot L125 is a polarization hologram optical element 99 of the 0th order light from the polarization diffractive optical element 98.
The + 1st-order diffracted light from the area 16 and the + 1st-order diffracted light from the area 17 are condensed on the boundary line between the light receiving portions 105 and 106.

The light spot L126 is a polarization hologram optical element 99 of the 0th order light from the polarization diffractive optical element 98.
Corresponding to the + 1st-order diffracted light from the area 16 and the + 1st-order diffracted light from the area 18, and is condensed on the boundary line between the light receiving portions 105 and 106.

The light spot L127 is a polarization hologram optical element 99 of the 0th order light from the polarization diffractive optical element 98.
The + 1st-order diffracted light from the area 16 and the + 1st-order diffracted light from the area 19 are condensed on the boundary line between the light receiving portions 107 and 108.

The light spot L128 is a polarizing hologram optical element 99 of the 0th order light from the polarizing diffractive optical element 98.
The + 1st-order diffracted light from the area 16 and the + 1st-order diffracted light from the area 20 are condensed on the boundary line between the light receiving portions 107 and 108.

Of the light receiving parts of the photodetector 97, the light receiving part 109
Denoted at 114 are sub-beam light-receiving units that are the + 1st-order diffracted light from the polarizing diffractive optical element 98, and light-receiving units 109 to 11 are provided.
1 is due to the region 15 of the polarizing hologram optical element 99 +
The light receiving portions for the first-order diffracted light, and the light-receiving portions 112 to 114 are light-receiving portions for the + 1st-order diffracted light by the region 16. Light receiving part 1
09 to 111 and the light receiving parts 112 to 114 are formed by dividing both ends in the radial direction of the rectangular light receiving part along the radial direction R by two dividing lines along the tangential direction T, respectively. .

That is, the light receiving section 110 receives the center portion in the radial direction of the + 1st order diffracted light divided by the region 15, and the respective light receiving sections 109 and 111 individually receive both end portions in the radial direction. Further, the light receiving unit 113 receives the center portion in the radial direction of the + 1st order diffracted light divided by the region 16, and the respective light receiving units 112 and 114 individually receive both end portions in the radial direction.

On the other hand, the light spot L129 is the + 1st-order diffracted light from the region 15 of the polarizing hologram optical element 99 out of the + 1st-order diffracted light from the polarizing diffractive optical element 98 and corresponds to the + 1st-order diffracted light from the region 17, The light is collected on the light receiving unit 109.

The light spot L130 is the + 1st order diffracted light from the region 15 of the polarization holographic optical element 99 out of the + 1st order diffracted light from the polarization diffractive optical element 98, and is the region 18
Corresponding to the + 1st order diffracted light from and is condensed on the light receiving unit 110.

The light spot L131 is the + 1st order diffracted light from the region 15 of the polarization holographic optical element 99 out of the + 1st order diffracted light from the polarization diffractive optical element 98 and is the region 19
Corresponding to the + 1st order diffracted light from and is condensed on the light receiving unit 110.

The light spot L132 is the + 1st order diffracted light from the region 15 of the polarizing hologram optical element 99 out of the + 1st order diffracted light from the polarizing diffractive optical element 98, and is the region 20.
Corresponding to the + 1st order diffracted light from and is condensed on the light receiving unit 111.

The light spot L133 is the + 1st order diffracted light from the region 16 of the polarization holographic optical element 99 out of the + 1st order diffracted light from the polarization diffractive optical element 98 and is the region 17
Corresponding to the + 1st-order diffracted light from and is condensed on the light receiving unit 112.

The light spot L134 is the + 1st order diffracted light from the region 16 of the polarization holographic optical element 99 among the + 1st order diffracted light from the polarization diffractive optical element 98, and is the region 18
Corresponding to the + 1st order diffracted light from and is condensed on the light receiving unit 113.

The light spot L135 is the + 1st order diffracted light from the region 16 of the polarization holographic optical element 99 out of the + 1st order diffracted light from the polarization diffractive optical element 98, and is the region 19
Corresponding to the + 1st order diffracted light from and is condensed on the light receiving unit 113.

The light spot L136 is the + 1st order diffracted light from the region 16 of the polarization holographic optical element 99 out of the + 1st order diffracted light from the polarization diffractive optical element 98, and is the region 20.
Corresponding to the + 1st order diffracted light from and is condensed on the light receiving unit 114.

Of the light receiving portions of the photodetector 97, the light receiving portion 115
Denoted at 120 are sub-beam light receiving portions that are the -1st order diffracted light beams from the polarizing diffractive optical element 98, and light receiving portions 115 to 11
7 is due to the region 15 of the polarization hologram optical element 99+
The light receiving portions for the first-order diffracted light, and the light-receiving portions 118 to 120 are light-receiving portions for the + 1st-order diffracted light by the region 16. Light receiving part 1
15 to 117 and the light receiving portions 118 to 120 are formed by dividing both ends in the radial direction of the rectangular light receiving portion along the radial direction R by two dividing lines along the tangential direction T, respectively. .

That is, the light receiving section 116 receives the center portion of the −first-order diffracted light divided by the region 15 in the radial direction, and the light receiving sections 115 and 117 individually receive both end portions in the radial direction. Further, the light receiving section 119 receives the center portion of the −first-order diffracted light divided by the region 16 in the radial direction, and the light receiving sections 118 and 120 individually receive both end portions in the radial direction.

On the other hand, the light spot L137 is the + 1st order diffracted light from the region 15 of the polarizing hologram optical element 99 out of the −1st order diffracted light from the polarizing diffractive optical element 98 and corresponds to the + 1st order diffracted light from the region 17. The light is condensed on the light receiving unit 115.

The light spot L138 is the + 1st order diffracted light from the region 15 of the polarizing hologram optical element 99 out of the −1st order diffracted light from the polarizing diffractive optical element 98, and is the region 18
Corresponding to the + 1st-order diffracted light from and is condensed on the light receiving unit 116.

The light spot L139 is the + 1st order diffracted light from the region 15 of the polarizing hologram optical element 99 out of the −1st order diffracted light from the polarizing diffractive optical element 98, and is the region 19
Corresponding to the + 1st-order diffracted light from and is condensed on the light receiving unit 116.

The light spot L140 is the + 1st order diffracted light from the region 15 of the polarizing holographic optical element 99 out of the −1st order diffracted light from the polarizing diffractive optical element 98, and is the region 20.
Corresponding to the + 1st order diffracted light from and is focused on the light receiving unit 117.

The light spot L141 is the + 1st order diffracted light from the region 16 of the polarizing hologram optical element 99 out of the −1st order diffracted light from the polarizing diffractive optical element 98, and is the region 17
Corresponding to the + 1st order diffracted light from and is condensed on the light receiving unit 118.

The light spot L142 is the + 1st order diffracted light from the region 16 of the polarizing hologram optical element 99 among the −1st order diffracted light from the polarizing diffractive optical element 98, and is the region 18
Corresponding to the + 1st-order diffracted light from and is condensed on the light receiving unit 119.

The light spot L143 is the + 1st order diffracted light from the region 16 of the polarizing holographic optical element 99 out of the −1st order diffracted light from the polarizing diffractive optical element 98 and is the region 19
Corresponding to the + 1st-order diffracted light from and is condensed on the light receiving unit 119.

The light spot L144 is the + 1st order diffracted light from the region 16 of the polarizing holographic optical element 99 in the −1st order diffracted light from the polarizing diffractive optical element 98, and is the region 20.
Corresponding to the + 1st-order diffracted light from and is condensed on the light receiving unit 120.

A semiconductor laser 96 and a mirror 100 are installed in the center of the front surface of the photodetector 97. Light emitted from the semiconductor laser 96 is reflected by the mirror 100 and travels toward the disk D1.

When the outputs from the light receiving units 101 to 120 are represented by V101 to V120, respectively, the signal processing circuit 20
1 is (V1
01 + V103 + V106 + V108)-(V102 +
It is calculated from the calculation of (V104 + V105 + V107) and output to the operation control means 200. In addition, the signal processing circuit 20
1 is a track error signal (V
101 + V102 + V105 + V106)-(V103
+ V104 + V107 + V108),
It is output to the operation control means 200. Further, the signal processing circuit 201 outputs the reproduction signal to V101 + V102 + V103.
+ V104 + V105 + V106 + V107 + V108
From the calculation of, for example, the optical information recording / reproducing apparatus 1
B is output to the connected upper device.

Further, the land / groove discrimination signal is
(V109 + V111 + V112 + V114)-(V1
10 + V113), (V115 + V117 + V118 +
V120)-(V116 + V119), or (V109
+ V111 + V112 + V114 + V116 + V11
9)-(V110 + V113 + V115 + V117 + V
118 + V120), but the determination signal generator 20 of the signal processing circuit 201
3 is (V109 + V111 + V112 + V114 + V
116 + V119)-(V110 + V113 + V115
+ V117 + V118 + V120) to calculate land /
A groove discrimination signal is calculated.

Focused spots L12 to L on the disc D1
Changes in the phases of the 0th order light and the ± 1st order diffracted lights from the disk D1 due to the positional deviation between the track 14 and the track D2 are as shown in FIGS.

In the optical information recording / reproducing apparatus 1B,
By the same method as the method described with reference to FIGS.
It is possible to detect which of the land and the groove of the disk D1 the 2-L14 are located on.

In the third embodiment, the polarizing diffractive optical element 98 is used as an optical element for slightly defocusing the focused spot of the sub beam in the radial direction on the disc. The polarizing diffractive optical element 98 is composed of a single region, the lens power is very weak, and the pattern of the grating can be regarded as straight lines at substantially equal intervals, so that in-plane position adjustment is unnecessary.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 17 to 19. It should be noted that, of the components shown in the present embodiment, the same components as those of the optical information recording / reproducing apparatus 1B described above are designated by the same reference numerals, and a duplicate description will be omitted.

FIG. 17 shows a block diagram of an optical information recording / reproducing apparatus 1C as the fourth embodiment. In this optical information recording / reproducing apparatus 1C, another polarizing hologram optical element 147 is arranged at the same position in place of the above-mentioned polarizing hologram optical element 99, and a photodetector 97 is replaced with a photodetector having a small number of light receiving portions. Optical head device 1 in which devices 146 are arranged at the same position
0C, and is different from the optical information recording / reproducing apparatus 1B in that it further includes a signal processing circuit 201C that generates various signals based on the output of the photodetector 146 instead of the signal processing circuit 201. The configuration is the same. Therefore, the arrangement of the focused spot on the disc D1 by the light emitted from the light source unit 202B is the same as that of the optical information recording / reproducing apparatus 1B (see FIG. 3). Further, the semiconductor laser 96 and the photodetector 146 are integrally installed in the module 145.

The above-mentioned polarizing hologram optical element 147.
Is approximately 1 as the ordinary light emitted from the semiconductor laser 96.
The reflected light from the disk D1 which is transmitted by 00% and transmitted through the quarter wavelength plate 5 in the forward path and the backward path is mostly diffracted as extraordinary light. The reflected light diffracted by the polarization hologram optical element 147 passes through the collimator lens 2 and is received by the photodetector 146. The photodetector 146 is installed in the middle of the two focal lines of the polarizing hologram optical element 147 and the collimator lens 2.

FIG. 18 shows a polarizing hologram optical element 147.
FIG. The polarizing hologram optical element 147 is
In the area including the effective diameter of the objective lens 6 shown by the dotted line in the figure,
For example, a two-layer diffraction grating including a proton exchange region and a dielectric film is formed on a lithium niobate substrate having birefringence. The direction of the grating in the diffraction grating is substantially parallel to the tangential direction (tangential direction) of the disc D1, and the pattern of the grating is a hyperbola whose asymptote is the tangential direction (tangential direction) and the radial direction (radial direction) of the disc D1. It is a state.

By properly designing the depth of the proton exchange region and the thickness of the dielectric film, the phase difference between the line portion and the space portion of the lattice can be independently defined for ordinary light and extraordinary light. With respect to the ordinary light on the outward path, assuming that the phase difference between the line portion and the space portion of the grating is 0, almost 100% of the incident light is transmitted as 0th-order light. On the other hand, with respect to extraordinary light on the return path, assuming that the phase difference between the line portion and the space portion of the grating is π, the incident light is ± 4th-order diffracted light of about 40.5%, respectively.
Is diffracted. Polarizing hologram optical element 147 is ± 1
A cylindrical lens acts on the diffracted light of the second order, and the generatrix of the diffracted light of the + 1st order and the generatrix of the diffracted light of the −1st order are + 45 ° and −, respectively, with respect to the radial direction of the disk D1.
It makes an angle of 45 °.

Next, the photodetector 146 described above will be described in detail. FIG. 19 shows the pattern of the light receiving portion of the photodetector 146 and the arrangement of the light spots on the photodetector 146.

The light receiving sections 148 to 151 of the photodetector 146 are the 0th order light of the polarizing diffractive optical element 98 and the light receiving section of the light spot L168 which is the + 1st order diffracted light by the polarizing hologram optical element 147. The portions 152 to 155 are light receiving portions of the light spot L169 which is the 0th order light of the polarizing diffractive optical element 98 and the −1st order diffracted light by the polarizing hologram optical element 147. These light receiving parts 148-15
1 and the light receiving portions 152 to 155 are formed by dividing each of the square light receiving surfaces into four by a dividing line along the tangential direction T and a dividing line along the radial direction R of the disc D1 passing through the optical axis. There is.

In addition, the light receiving portions 156 to 1 of the photodetector 146.
Reference numeral 58 denotes a light receiving portion of the light spot L170 which is the + 1st order diffracted light of the polarizing diffractive optical element 98 and the + 1st order diffracted light by the polarizing holographic optical element 147.
Reference numerals 9 to 161 are light receiving portions of the light spot L171 which is the + 1st order diffracted light of the polarizing diffractive optical element 98 and the −1st order diffracted light by the polarizing holographic optical element 147. Each of the light receiving portions 156 to 158 and the light receiving portions 159 to 161 is formed by dividing a square light receiving surface into two parts by two dividing lines parallel to the tangential direction T of the disc D1 passing through the optical axis.

Further, the light receiving parts 162 to 1 of the photodetector 146.
Reference numeral 64 denotes a light receiving portion of the light spot L172 which is the −1st order diffracted light of the polarizing diffractive optical element 98 and the + 1st order diffracted light by the polarizing holographic optical element 147.
Reference numerals 5 to 167 are the light receiving portions of the light spot L173 which is the −1st order diffracted light of the polarizing diffractive optical element 98 and the −1st order diffracted light by the polarizing hologram optical element 147. Each of the light receiving portions 162 to 164 and the light receiving portions 165 to 167 is formed by dividing a square light receiving surface into three by two dividing lines parallel to the tangential direction T of the disc D1 passing through the optical axis.

The light spots L168 to L17 described above are used.
3 is individually received by the photodetector 146 in a state of being rotated 90 degrees by the action of the polarization hologram optical element 147 and the collimator lens 2. Therefore, each ± first-order diffracted light (light spots L170 to L170) by the polarizing diffractive optical element 98 is
As described above, the light receiving surface 173) is received by the three light receiving portions formed by partitioning the light receiving surface in parallel with the tangential direction of the disc D1 passing through the optical axis. Therefore, each of the ± first-order diffracted lights is individually received at the central portion and both end portions in the radial direction.

Further, since the two generatrixes of the ± 1st-order diffracted light of the polarizing hologram optical element 147 are orthogonal to each other, the light spots L168, L170, L172 and the light spots L169, L171, L173 have vertical and horizontal intensities. The distributions are opposite to each other.

A semiconductor laser 96 and a mirror 100 are installed in the center of the front surface of the photodetector 97. Light emitted from the semiconductor laser 96 is reflected by the mirror 100 and travels toward the disk D1.

When the outputs from the light receiving sections 148 to 167 are represented by V148 to V167, respectively, the signal processing circuit 20
1C shows the focus error signal by (V
148 + V151 + V153 + V154)-(V149
+ V150 + V152 + V155),
It is output to the operation control means 200. In addition, the signal processing circuit 2
01C is a push-pull method for the track error signal,
(V148 + V150 + V153 + V155)-(V1
49 + V151 + V152 + V154), and outputs it to the operation control means 200. Further, the signal processing circuit 201C outputs the reproduction signal to V148 + V149 + V.
150 + V151 + V152 + V153 + V154 + V
It is calculated from the calculation of 155, and is output to a higher-level device to which the optical information recording / reproducing device 1C is connected, for example.

Further, the land / groove discrimination signal is
(V156 + V158 + V159 + V161)-(V1
57 + V160), (V162 + V164 + V165 +
V167)-(V163 + V166), or (V156
+ V158 + V159 + V161 + V163 + V16
6)-(V157 + V160 + V162 + V164 + V
165 + V167), but the discrimination signal generator 2 of the signal processing circuit 201C can be calculated.
03C is (V156 + V158 + V159 + V161
+ V163 + V166)-(V157 + V160 + V1
The land / groove discrimination signal is calculated from the calculation of (62 + V164 + V165 + V167).

Focused spots L12 to L on the disc D1
The phase changes of the 0th-order light and the ± 1st-order diffracted lights from the disk D1 due to the positional deviation between the track 14 and the track D2 are as shown in FIGS.

In the optical information recording / reproducing apparatus 1C,
By the same method as the method described with reference to FIGS.
It is possible to detect which of the land and the groove of the disk D1 the 2-L14 are located on.

In the fourth embodiment, the polarizing diffractive optical element 98 is used as an optical element for slightly defocusing the focused spot of the sub beam in the radial direction on the disc. The polarizing diffractive optical element 98 is composed of a single region, the lens power is very weak, and the pattern of the grating can be regarded as straight lines at substantially equal intervals, so that in-plane position adjustment is unnecessary.

Each of the above-mentioned optical information recording / reproducing devices 1, 1
In A, 1B, and 1C, a diffractive optical element or a polarizing diffractive optical element that functions as a concave lens for + 1st-order diffracted light and a convex lens for −1st-order diffracted light corresponds to + 1st-order diffracted light. The condensing spot is formed in front of the condensing point when viewed from the incident side, and the condensing spot corresponding to the −1st order diffracted light is formed farther from the condensing point when viewed from the incident side.

On the other hand, for the + 1st order diffracted light, the generatrix acts as a cylindrical concave lens parallel to the tangential direction of the disc, and for the -1st order diffracted light, the generatrix is a cylinder whose parallel to the tangential direction of the disc. +1 by a diffractive optical element or a polarizing diffractive optical element that functions as a convex lens
A focused spot corresponding to the diffracted light of the second order is formed in front of the focused line parallel to the tangential direction of the disc when viewed from the incident side, and a focused spot corresponding to the -1st order diffracted light is viewed from the incident side of the disc. It is also conceivable that the light beam is formed farther than the condensing line parallel to the direction.

Such a diffractive optical element or a polarizing diffractive optical element, which is an optical element for slightly defocusing the focused spot of the sub-beam in the radial direction on the disc, is composed of a single region and has a lens power. Is very weak, and the pattern of the lattice can be regarded as straight lines at substantially equal intervals, so that in-plane position adjustment is unnecessary.

In each of the above-mentioned optical information recording / reproducing devices 1, 1A, 1B and 1C, the light emitted from the semiconductor laser is made to be 0 by the diffractive optical element or the polarizing diffractive optical element.
The light is divided into three lights, that is, the primary light and the ± first-order diffracted light, and the 0th-order light is used as the main beam and the ± first-order diffracted light is used as the sub-beam. On the other hand, the emitted light from the semiconductor laser is divided into two lights of 0-order light and + 1st-order diffracted light or -1st-order diffracted light by a diffractive optical element or a polarizing diffractive optical element.
A mode in which only one of the primary light and the + 1st-order diffracted light or the -1st-order diffracted light is used as the sub-beam is also considered.

Further, the emitted light from one semiconductor laser is divided into two or three by a diffractive optical element or a polarizing diffractive optical element.
Instead of splitting into one light and using it as a main beam and a sub beam, it is also possible to consider the form which uses the emitted light from two or three semiconductor lasers as a main beam and a sub beam, respectively.

In this case, slightly defocusing the focused spot of the sub-beam on the disk in the radial direction means that the position of the semiconductor laser of the sub-beam is shifted to the front or the rear of the focus of the collimator lens, or to the collimator lens. In the optical path of the sub-beam between the objective lenses,
It can be realized by a configuration in which a concave lens or a convex lens, or a cylindrical concave lens or a cylindrical convex lens whose generatrix is parallel to the tangential direction of the disc is further inserted.

As described above, when the position of the sub-beam semiconductor laser is shifted to the front or rear of the focal point of the collimator lens, an optical element for slightly defocusing the focused spot of the sub-beam on the disk in the radial direction is not necessary. is there. On the other hand, when further inserting a concave lens or a convex lens or a cylindrical concave lens or a cylindrical convex lens whose generatrix is parallel to the tangential direction of the disc in the optical path of the sub-beam between the collimator lens and the objective lens, the focused spot of the sub-beam on the disc Such a concave lens or a convex lens, which is an optical element for slightly defocusing in the radial direction, or a cylindrical concave lens or a cylindrical convex lens, is composed of a single region, and the lens power is very weak, and the surface is almost flat. Therefore, it is not necessary to adjust the position within the plane.

[0204]

The optical head device and the optical information recording / reproducing device according to the present invention generate the main beam and the sub beam from the light emitted from the light source, and when the focused spot of the main beam is focused on the disk. Since it has an optical element for defocusing the focused spot of the sub-beam on the disc, depending on whether the focused spot is located on the land or on the groove, the central portion and both end portions of the reflected light of the sub-beam are And the 0th order light from the disk
It is possible to cause a phase difference between the first-order diffracted lights, and it is possible to cause a difference in light intensity between them.

On the other hand, according to the present invention, since the photodetector is provided with the light receiving portions for individually receiving the reflected light of the sub-beam at the central portion and both end portions in the radial direction, the central portion and the both end portions of the reflected light of the sub-beam are provided. It is possible to observe the difference in light intensity between the part and the part, and based on this, it is possible to determine whether the focused spot of the sub beam is on the land or on the groove. Also, by setting the relative positional relationship between the sub beam and the main beam in advance, it is possible to obtain a determination signal for determining whether the focused spot of the main beam is on the land or the groove from the determination of the sub beam. Is possible.

Further, according to the present invention, if the relative positional relationship between the main beam and the sub beam is clear, it is not necessary to set the positional relationship between the main beam and the sub beam in accordance with the track pitch as in the conventional case. It is possible to perform land / groove identification for a wide variety of optical recording media having different pitches.

Further, since the present invention can be realized by an optical element which provides a predetermined difference in the distance from the objective lens of the main beam and the sub beam to each condensing point, the diffraction divided into a plurality of regions as in the conventional case. The optical element is not essential, and thus it is possible to eliminate the difficulty of adjusting the position of the optical element.

Further, in the case of the optical information recording / reproducing apparatus according to the present invention, the operation control means is provided with a judgment advance function for performing the track servo pull-in operation after receiving the land / groove judgment signal. Since it is known in advance whether the focused spot is located on the land or on the groove, the track servo pull-in operation can be performed stably, and the track servo runaway can be effectively avoided. Is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a plan view of the diffractive optical element disclosed in FIG.

3A and 3B show an arrangement of focused spots on a disc by the optical head device disclosed in FIG. 1, FIG. 3A is a view seen from the disc surface, and FIG. 3B is FIG. ) Is a view seen from a line of sight along the radial direction.

4 (A) is a plan view of the hologram optical element disclosed in FIG. 1, and FIG. 4 (B) is a rear view.

5 is a front view showing the arrangement of light spots with respect to the photodetector disclosed in FIG. 1 and its light receiving portion. FIG.

FIG. 6 is a diagram showing a 0th-order light beam from a disc for a main beam,
It is explanatory drawing which shows the positional relationship of +/- 1st order diffracted light.

FIG. 7 is a diagram showing changes in the phases of 0th-order light and ± 1st-order diffracted light from the disc due to the position shift of the focused spot of the main beam on the disc and the track, and FIG. Fig. 7 shows a state in which the groove is illuminated on the groove.
FIG. 7B is a cross-sectional view perpendicular to the disk surface of the 0th-order light and ± 1st-order diffracted light at that time and along the radial direction, and FIG. 7C shows the light beam at the boundary between the groove and the land. FIG. 7 (D) shows a state of being irradiated, and FIG. 7 (D) shows a sectional view perpendicular to the disk surface of the 0th-order light and the ± 1st-order diffracted light at that time, which is perpendicular to the disk surface, and FIG. Shows a state in which the light beam is applied to the land, and FIG.
FIG. 7F shows a cross-sectional view of the 0th-order light and the ± 1st-order diffracted light at that time, which is perpendicular to the disk surface of the equiphase surface and along the radial direction, and FIG. 7G shows the light beam at the boundary between the land and the groove. FIG. 7 (H) is a cross-sectional view perpendicular to the disk surface of the equiphase surface of the 0th-order light and the ± 1st-order diffracted lights and along the radial direction.

FIG. 8 is an explanatory diagram showing a positional relationship of 0th-order light and ± 1st-order diffracted light from a disc with respect to one sub-beam.

FIG. 9: Zero-order light from the disc due to the displacement of the focused spot of one sub-beam on the disc and the track, ±
FIG. 9A is a diagram showing a change in the phase of the first-order diffracted light and is shown in FIG.
Indicates a state where the light beam is applied to the groove,
FIG. 9B is a cross-sectional view of the 0th-order light and the ± 1st-order diffracted lights at that time, which is perpendicular to the disk surface of the equiphase surface and along the radial direction, and FIG. FIG. 9D shows a state in which the boundary is illuminated, and FIG. 9D is a cross-sectional view perpendicular to the disk surface of the equal phase plane of the 0th order light and the ± 1st order diffracted lights at that time and along the radial direction.
FIG. 9E shows a state in which the light beam is irradiated onto the land, and FIG. 9F shows a state in which the 0th-order light and the ± 1st-order diffracted light at that time are perpendicular to the disk surface of the equiphase surface and along the radial direction. FIG. 9 (G) shows a cross-sectional view, and FIG. 9 (G) shows a state in which the light beam is applied to the boundary between the land and the groove, and FIG. 9 (H) shows the equiphase surfaces of the 0th-order light and the ± 1st-order diffracted lights at that time. FIG. 3 is a cross-sectional view perpendicular to the disc surface and along the radial direction.

FIG. 10: 0 from the disc for the other sub-beam
It is explanatory drawing which shows the positional relationship of 2nd light and +/- 1st-order diffracted light.

FIG. 11: 0th-order light from the disc due to the displacement of the focused spot of the other sub-beam on the disc and the track,
FIG. 12 is a diagram showing changes in the phase of ± first-order diffracted light.
FIG. 11A shows a state in which the light beam is applied to the groove, and FIG. 11B shows a state in which the 0th order light and the ± 1st order diffracted lights are perpendicular to the disk surface of the equiphase surface and along the radial direction. FIG. 11C shows a cross-sectional view, and FIG. 11C shows a state in which the light beam is applied to the boundary between the groove and the land.
FIG. 11D is a sectional view of the 0th-order light and the ± 1st-order diffracted light at that time, which is perpendicular to the disk surface of the equiphase surface and along the radial direction, and FIG. 11E shows the light beam irradiated on the land. 11 (F) is a sectional view taken along the radial direction perpendicular to the disk surface of the 0th-order light and the ± 1st-order diffracted light at that time, and FIG. 11 (G) shows the light beam. Shows the state where the boundary between the land and the groove is irradiated, and FIG. 11 (H) is a sectional view perpendicular to the disk surface of the 0th-order light and ± 1st-order diffracted light at that time and along the radial direction. Show.

12A is a diagram showing a track error signal generated by a signal processing circuit, and FIG. 12B is a diagram showing a land / groove determination signal obtained from only one sub-beam. FIG. 12C is a diagram showing a land / groove discrimination signal obtained only from the other sub-beam, and FIG. 12D is obtained from a subtracted value of the discrimination signals of FIGS. 12B and 12C. FIG. 6 is a diagram showing a land / groove discrimination signal.

FIG. 13 is a block diagram showing a second embodiment.

FIG. 14 is a front view showing the arrangement of light spots with respect to the photodetector disclosed in FIG. 13 and its light receiving portion.

FIG. 15 is a block diagram showing a third embodiment.

16 is a front view showing the arrangement of light spots with respect to the photodetector disclosed in FIG. 15 and its light receiving portion.

FIG. 17 is a block diagram showing a fourth embodiment.

18 is a plan view of the polarization hologram optical element disclosed in FIG. 17. FIG.

FIG. 19 is a front view showing the arrangement of light spots with respect to the photodetector disclosed in FIG. 17 and its light receiving portion.

FIG. 20 is a block diagram of a conventional example.

FIG. 21 is an explanatory diagram showing the arrangement of focused spots on a disk according to a conventional example.

22 is a front view showing the arrangement of light spots with respect to the photodetector disclosed in FIG. 20 and its light receiving portion.

23A is a diagram showing a track error signal generated by a conventional signal processing circuit, and FIG. 23B is a diagram showing a land / groove discrimination signal obtained from only one sub-beam. FIG. 23 (C) is a diagram showing a land / groove discrimination signal obtained from only the other sub-beam, and FIG. 23 (D) is obtained from subtracted values of the discrimination signals of FIGS. 23 (B) and 23 (C). It is a figure which shows the determined land / groove discrimination signal.

[Description of Reference Signs] 1,1A, 1B, 1C Optical information recording / reproducing device 3 Diffractive optical element 6 Objective lens 7,96 Semiconductor laser (light source) 8 Holographic optical element 10, 10A, 10B, 10C Optical head device 11, 81 , 97, 146 Photodetectors 21-40, 82-91, 101-120, 148-1
67 Light receiving section 98 Polarizing diffractive optical element 99, 147 Polarizing hologram optical element 200 Operation control means 201, 201A, 201C Signal processing circuit 202, 202B Light source section 203, 203A, 203C Discrimination signal generating section 204 Judgment advance function D1 disc ( Optical recording medium) D2 track D3 groove D4 lands L12, L13, L14 focused spots L41 to L64, L92 to L94, L121 to L14
4, L168 ~ L173 light spot (reflected light)

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 7/135 G11B 7/09 G11B 7/125 G11B 7/13

Claims (17)

(57) [Claims] 1. A light source unit for emitting a main beam and a sub beam, an objective lens for converging each of the beams on an optical recording medium, and a photodetector for receiving reflected light from the optical recording medium. The light source unit sets a distance between the main beam and the sub beam from the objective lens to a condensing point at least in a radial direction of the optical recording medium by 0.1 to 1.0 [μ.
m], the photodetector is provided with a light receiving portion for each of the main beam and the sub beam, and the light receiving portion for the sub beam is a central portion and both end portions in the radial direction of the sub beam. By receiving and
An optical head device characterized in that a land / groove discrimination signal is obtained . 2. The light source unit emits the main beam and the sub beam so that respective focused spots are formed on the same track of the optical recording medium. Optical head device. 3. The light source unit is disposed between the light source that emits a single laser beam and the light source, and the objective lens,
A diffractive optical element or a diffractive diffractive optical element that divides the light emitted from the light source into a plurality of lights, and forms the main beam by the 0th order light of the diffractive optical element or the diffractive diffractive optical element, The optical head device according to claim 1, wherein the sub-beam is formed by either one of ± 1st-order diffracted lights. 4. The light source section is disposed between the light source that emits a single laser beam and the light source, and the objective lens,
A diffractive optical element or a diffractive diffractive optical element that divides the light emitted from the light source into a plurality of lights, and forms the main beam by the 0th order light of the diffractive optical element or the diffractive diffractive optical element, 3. The optical head device according to claim 1, wherein the two sub-beams are formed by both of the ± first-order diffracted lights, and the photodetector has the light-receiving unit for each sub-beam. 5. The diffractive optical element or the polarizing diffractive optical element has a function of acting as a concave lens for the + 1st order diffracted light and a function of acting as a convex lens for the −1st order diffracted light. The optical head device according to claim 4. 6. The diffractive optical element or the polarizing diffractive optical element is configured such that a distance from the objective lens to a condensing point when condensing each of the beams on the optical recording medium is +1.
6. The optical head device according to claim 5, wherein the diffracted light has a function of extending the diffracted light longer than the 0th order light and the −1st order diffracted light shorter than the 0th order light. 7. The optical head device according to claim 6, wherein the grating pattern of the diffractive optical element or the polarizing diffractive optical element is set in a concentric arc shape. 8. The diffractive optical element or the polarizing diffractive optical element has a function of acting as a cylindrical concave lens whose generatrix is parallel to the tangential direction of the optical recording medium with respect to the + 1st order diffracted light, and the −1st order diffracted light. 5. The optical head device according to claim 4, wherein the busbar functions as a cylindrical convex lens parallel to the tangential direction of the optical recording medium. 9. The diffractive optical element or the polarizing diffractive optical element is characterized in that the distance from the objective lens to the converging line in the tangential direction when converging each of the beams on the optical recording medium is 0 for the + 1st order diffracted light
9. The optical head device according to claim 8, wherein the optical head device has a function of extending the light longer than the next light and shortening the −1st diffracted light more than the 0th light. 10. The optical head device according to claim 1, wherein the light source unit includes a plurality of light sources that individually emit the main beam and the sub beam. 11. A collimator lens is arranged between the light source unit and the objective lens, and the light source of the sub-beam is arranged so as to be displaced forward or backward of the focal point of the collimator lens. The optical head device described. 12. A collimator lens is provided between the light source unit and the objective lens, and in the optical path of the sub-beam,
The optical head device according to claim 10, wherein a concave lens or a convex lens is inserted. 13. A collimator lens is provided between the light source unit and the objective lens, and in the optical path of the sub-beam,
11. The optical head device according to claim 10, wherein a bus bar is inserted with a cylindrical concave lens or a cylindrical convex lens parallel to the tangential direction of the optical recording medium. 14. A light source unit that emits a main beam and a sub beam, an objective lens that focuses each of the beams on an optical recording medium, and a photodetector that receives reflected light from the optical recording medium. The light source unit includes an optical element that shifts a distance from the objective lens to a condensing point of the main beam and the sub beam in at least a radial direction of the optical recording medium, and the photodetector includes the main beam and A light receiving unit for each of the sub-beams is provided, and the light receiving unit for the sub-beams individually receives the central portion and both end portions of the sub-beam in the radial direction, and focusing and tracking of the optical head device. Head drive means for performing the above operation, operation control means of the head drive means, and a drive based on the output of the photodetector. And a signal processing circuit that generates a focus error signal, a track error signal, and a reproduction signal, wherein the signal processing circuit determines a focused spot of the main beam on the optical recording medium based on an output of a light receiving unit for the sub beam. An optical information recording / reproducing apparatus having a discrimination signal generating section for generating a discrimination signal indicating whether it is located in a land or a groove. 15. The discrimination signal generation unit generates the discrimination signal from a subtracted value of an output of a light receiving unit that receives both end portions of an output of a light receiving unit that receives the central portion of the sub-beam in the radial direction. 15. The method according to claim 14,
The described optical information recording / reproducing apparatus. 16. A light source section for emitting a main beam and a sub beam, an objective lens for converging each beam on an optical recording medium, and a photodetector for receiving reflected light from the optical recording medium. The light source unit is disposed between the light source that emits a single laser beam and the objective lens, divides the light emitted from the light source into a plurality of lights, and uses the 0th-order light to emit the main light. A beam is formed, and the two sub-beams are formed by both ± 1st-order diffracted light, and the distance from the objective lens to the condensing point of the main beam and the two sub-beams is at least the radial direction of the optical recording medium. A diffractive optical element or a polarizing diffractive optical element that shifts with respect to each other, and the photodetector includes a light receiving unit for each of the main beam and the two sub beams, and The light receiving unit for the optical system includes an optical head device that individually receives the central portion and both end portions of the sub-beam in the radial direction, a head driving unit that performs focusing and tracking of the optical head device, and a head driving unit of the head driving unit. An operation control unit and a signal processing circuit that generates a focus error signal, a track error signal, and a reproduction signal based on the output of the photodetector are provided, and the signal processing circuit is based on the output of the light receiving unit for each of the sub-beams. A discriminating signal generator for generating a discriminating signal indicating whether the focused spot of the main beam on the optical recording medium is located in the land or the groove, and the central portion of the + 1st order diffracted light in the radial direction. The subtraction value of the output of the light receiving unit that receives both ends with respect to the output of the light receiving unit that receives An optical information recording / reproducing apparatus, wherein the discrimination signal is generated based on a difference between an output of a light receiving unit that receives the central portion in the radial direction and a subtraction value of an output of the light receiving units that receive both end portions. 17. The operation control means has a judgment advance function of performing a track servo pull-in operation after receiving the judgment signal from the signal processing circuit when accessing a predetermined track of the optical recording medium. The optical information recording / reproducing apparatus according to claim 14, 15 or 16, wherein