JPH0566656B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to an apparatus for recording and reproducing information at minute track intervals on an optical information recording medium that does not have a guide groove. The present invention relates to a device suitable for recording a new information signal in an adjacent unrecorded area while tracking the information signal.

[Background of the invention]

In order to record information on an optical information recording medium at minute track intervals, conventionally a guide groove (pre-group) is provided in the optical information recording medium in advance, and information signals are recorded while tracking in the guide groove. There is. However, such a conventional optical information recording method has a problem in that the shape of the guide groove is poor and the S/N ratio of the reproduced signal is reduced. Also,
Since the guide grooves must be formed in advance on the recording medium, there is a problem in that the manufacturing cost of the recording medium increases. As a way to improve this,
For example, as shown in Japanese Patent Publication No. 57-58734,
When recording the nth track information, n-
It is known that the information recorded on the first track is used as a guide track.

In this method, since information is recorded on a flat track, there is no deterioration in the S/N ratio of the reproduced signal. Also,
Since the distance between adjacent tracks can be kept small, signals can be recorded at high density. Furthermore, since it is not necessary to form guide grooves in advance on the recording medium, there is an effect that the manufacturing cost of the recording medium is also reduced. However, no effective means for specifically implementing this method is known (Japanese Unexamined Patent Publication No. 55
-125546, JP 56-22230, JP 56-54643, JP 56-119941,
JP-A-57-40760, JP-A-57-53836, JP-A-58-91539, JP-A-58-98852, JP-A-58-102343, JP-A-58-
200435, Japanese Patent Application Laid-open No. 59-30250). Also,
A method for measuring the spacing of information tracks is known, as shown in Japanese Patent Application Laid-Open No. 58-102343, but this method does not recognize the problem of recording new information signals on adjacent tracks. do not have.

[Purpose of the invention]

An object of the present invention is to specifically realize a method of recording a new information signal in an adjacent unrecorded area while tracking an information track on which an information signal has already been recorded in an optical information recording medium that does not have a guide groove. An object of the present invention is to provide an optical information recording/reproducing device equipped with an effective means for performing the following steps.

[Summary of the invention]

In order to achieve the above object, in the present invention, a beam from a light source is divided into a recording beam of the 0th order diffraction beam and a recording beam of the 1st order diffraction beam using a diffraction grating.
It is separated into a tracking beam and a second tracking beam. Then, the first tracking beam is placed before the recording beam and between the first information track on which the information signal has already been recorded and the unrecorded area, and the second tracking beam is placed before the recording beam. , a second information track arranged after the recording beam and formed by recording an information signal in an unrecorded part adjacent to the first information track, sandwiching the second information track from the first information track. is placed on the opposite side. The recording beam forms a second information track based on the outputs of the first and second photodetectors that respectively detect the reflected lights of the first and second tracking beams.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of an optical disk 1, which is an optical information recording medium. Information signals are recorded on the optical disc 1 as concentric or spiral tracks 2. The information track 2 is recorded by changes in reflectance due to thermal transformation of the surface of a recording film provided on the optical disk 1, for example. Reproduction detects changes in the amount of reflected light. In this embodiment, the reflectance of the information track 2 will be explained as being higher than the reflectance of other parts. Further, information track 2 will be described as being able to be played back immediately after being recorded.

FIG. 2 is a schematic block diagram of an embodiment of an optical information recording/reproducing apparatus based on the present invention. In FIG. 2, the optical disk 1 shown in FIG. 1 is attached to a rotating shaft 4 of an electric motor 3 and driven at a constant angular velocity or constant linear velocity. A beam 6 emitted from a semiconductor laser 5 as a light source is passed through a collimator lens 7, a diffraction grating 8, a polarizing beam splitter 9, and a 1/4
The light is irradiated onto the optical disk 1 via the wavelength plate 10 and the objective lens 11. Here, the diffraction grating 8 has a light beam 6
The recording beam 6a of the 0th order diffraction beam and the two 1
Beams 6b and 6c for tracking the next diffracted beam
Divide into.

FIG. 3 shows these recording beams 6a and tracking beams 6 irradiated onto the optical disk 1.
It shows the positional relationship between b and 6c. In FIG. 3, it is assumed that the information track 2 is formed from the right side to the left side. Further, it is assumed that the optical disk 1 moves from the upper side to the lower side. In order to scan the recording beam 6a onto the information track 2a,
One tracking beam 6b is arranged above the recording beam 6a and between the information track 2a and the information track 2b located on the right side thereof, and the other tracking beam 6c is arranged above the recording beam 6a.
It is placed below the information track 2a and on the opposite side of the information track 2b, that is, on the left side.

FIG. 17 shows the configuration of the diffraction grating 8 for realizing the beam arrangement shown in FIG. 3. Third
In the figure, P is the track pitch and S is the beam 6.
a and beam 6b, and beam 6a and beam 6c
is the spacing in the track pitch direction. In the example, it was set as S=P/2 (1). l is the distance between beam 6a and beam 6b and beam 6a and beam 6c, and θ is beam 6
Assuming the angle between the straight line passing through a, 6b, and 6c and the information track 2, S=lsinθ...(2). Therefore, θ=sin ^-1 (S/l) ...(3) ∴ θ=sin ^-1 (P/2l) ...(4) holds true. Therefore, the grating lines 8 of the diffraction grating 8
The angle between a and the radial direction of the disk 1 is set to θ. On the other hand, the focal length of the objective lens 11 is
When α is the diffraction angle (not shown) of fobj and beams 6b and 6c, l=fobj·tan α (5). Further, if the grating pitch of the diffraction grating 8 is d and the wavelength is λ, then dsinα=λ (6) holds true. Therefore, d=λ/sinα...(7) ∴d=λ/sintan ^-1 (l/fobj)...(8). For example, if fobj=4.5mm, λ=830nm, l=20μm, P=1.6μm, then from equation (4), θ=sin ^-1 (1.6×10 ^-3 /2×20×10 ^-3 ) ≒2.3 ° Also, from equation (8), d=830×10 ^-6 /sintan ^-1 (20×10 ^-3 /4.5) ≒0.19mm.

Beams 6a, 6 irradiated onto the optical disk 1
b and 6c are reflected and passed through the objective lens 11 and 1/4 wavelength plate 10 again, reflected by the polarizing beam splitter 9, and then sent to the respective split photodetectors 15a and 15 via the convex lens 12, concave lens 13, and cylindrical lens 14.
b, 15c. In this case the photodetector 15
a generates an information signal and a focus error detection signal, which drives the focus control coil 18 of the objective lens 11 through the focus error detection circuit 16 and the focus control circuit 17, so that the beams 6a, 6b, and 6c are always directed to the optical disk 1. The objective lens 11 is converged upward.
control the vertical position of In addition, the photodetector 15b, 1
5c generates a tracking error detection signal, drives the tracking control coil 21 of the objective lens 11 through the tracking error detection circuit 19 and the tracking control circuit 20, and generates the beams 6a, 6b, 6.
c is always information track 2a, 2 on optical disk 1
Objective lens 1 is placed at a predetermined position relative to b.
Control 1. Additionally, the tracking control circuit 20
The optical transfer table 22 is moved by the transfer drive mechanism 23 using a part of the output.

The principle of tracking error detection in this embodiment will be explained below.

FIG. 4 is a graph of the intensity of light reflected by one surface of the optical disk and detected by photodetectors 15b and 15c. The horizontal axis represents the position of the beams 6b, 6c in the direction perpendicular to the axis of the information track 2, and the vertical axis represents the intensity of the light. As can be seen, the intensity of the light is maximum when the beam is in the center of the information tracks 2 and minimum when the beam is in the area between the information tracks 2. Also,
Area without information track 2, i.e. beam 6
It can be seen that when the beam is in the region to the left of b and 6c, the intensity asymptotically approaches a constant value determined by the reflectance of the unrecorded portion of the optical disc 1. In addition, the solid line is beam 6
The intensity for beam 6c is the intensity for b, and the dashed line is the intensity for beam 6c. The graph shows two points 24b, 24c, which correspond to the beams 6b, 6c (Fig. 3).
corresponds to the intensity of light detected by the respective photodetectors 15b, 15c associated with.

FIG. 5 shows a block diagram of a tracking error detection circuit of an optical information recording/reproducing apparatus according to the present invention. As shown in the figure, the outputs of the photodetectors 15b and 15c are input to a differential amplifier 25, and a tracking error detection signal is output. When the tracking control is applied, the objective lens 11 is controlled so that the outputs of the photodetectors 15b and 15c become equal after all.
Here, when the objective lens 11 moves, the three beams 6a, 6b, 6c on the optical disk 1 move together.

Now, consider a case where the position of the recording beam 6a shifts to the left as shown in FIG. FIG. 7 is a graph of light intensity in the case of FIG. Figures 7 and 4
Comparing the figures, it can be seen that the position of point 24b has moved downward. This is because the beam 6b and the information track 2b are too far apart. On the other hand, point 2
The vertical position of the beam 4c does not change because the relative position of the beam 6a and the beam 6c does not change, so that the distance between the information track 2a formed by the beam 6a and the beam 6c is kept constant.
In this way, when the position of the recording beam 6a shifts to the left, the output of the photodetector 15b becomes smaller than the output of the photodetector 15c, so a negative signal is output as the tracking error detection signal. Ru.

Next, consider a case where the position of the recording beam 6a shifts to the right as shown in FIG. Figure 9 shows the 8th
It is a graph of light intensity in the case shown in the figure. Comparing FIG. 9 with FIG. 4, it can be seen that the position of point 24b has moved upward. This is because the beam 6b and the information track 2b are too close. On the other hand, point 2
The vertical position of 4c does not change for the reasons stated above. In this way, when the position of the recording beam 6a shifts to the right, the output of the photodetector 15b becomes larger than the output of the photodetector 15c, so a positive signal is output as the tracking error detection signal. Ru.

As described above, according to the embodiment of the present invention, it is possible to obtain a tracking error detection signal optimal for tracking control while recording an information signal. new information signals can be recorded on the tracks that

The tracking error detection when an information signal is recorded has been described above. Next, the tracking error detection when an information signal is reproduced will be explained. To reproduce the information signal, the optical information recording/reproducing device (FIG. 2) used for recording is used as is. However, as shown in FIG. 10, the positional relationship of the beams 6a, 6b, and 6c irradiated onto the optical disk 1 is changed, and the intensity of the recording beam 6a is lowered to be used as the reproducing beam 6a. That is, in order to scan the information track 2a with the reproduction beam 6a, one tracking beam 6b is placed above the reproduction beam 6a and slightly to the left of the information track 2a, and the other tracking beam 6c is placed above the information track 2a. It is placed below the reproduction beam 6a and slightly to the right of the information track 2a.

FIG. 18 shows the configuration of the diffraction grating 8 for realizing the beam arrangement shown in FIG. 10. In this embodiment, since the diffraction grating 8 used during recording is used, the grating pitch d is the same. On the other hand, the 10th
In the figure, S≒P/4 is set as (9), so by substituting this into equation (3), θ≒sin ^-1 (P/4l). When the values of P and l are set as during recording, θ≒sin ⁻¹ (1.6×10 ⁻³ /4×20×10 ³ )≈1.1°. That is, the setting angle of the diffraction grating 8 during recording is θ≒2.3° (clockwise), and during playback, θ≒
Set to 1.1° (counterclockwise).

FIG. 11 is a graph of the light intensity in the case of FIG. Three points 24a, 24b on the graph,
24c is the same as in FIG. 4, the beams 6a, 6b, 6
the respective photodetectors 15a, 15 associated with c.
b, corresponds to the intensity of light detected by 15c. Further, the tracking error detection circuit used in reproduction may be the one shown in FIG.

The principle of tracking error detection during playback is the same as the three-beam method, which is a tracking error detection method used in existing optical disk playback devices, so a description thereof will be omitted.

Now, it is necessary to change the positional relationship of the beams 6a, 6b, 6c on the disk 1 between recording and reproduction. These beams 6a, 6b, 6c
In order to change the positional relationship, the diffraction grating 8 may be rotated by a predetermined angle.

As described above, according to the embodiment of the present invention, by switching the set angle of the diffraction grating 8 between recording and reproduction, tracking is possible both during recording and reproduction.

FIG. 20 is a schematic block diagram of an embodiment of an optical information recording/reproducing apparatus based on the present invention.
This is the configuration shown in FIG. 2 described above with the addition of means for switching between recording and reproduction. That is,
A controller 31 that controls the entire apparatus controls a rotating means 32 attached to the diffraction grating 8 to a predetermined set angle during recording and during reproduction.

Next, another embodiment of the present invention will be described in which tracking can be detected without changing the positional relationship of the beams 6a, 6b, 6c on the disk 1 between recording and reproduction.

FIG. 12 shows the positional relationship of the beams 6a, 6b, and 6c on the optical disk 1 during recording. In FIG. 3, beam 6b and information track 2b
The arrangement was such that the interval between the beam 6c and the information track 2a was equal to that between the beam 6c and the information track 2a. In FIG. 12, this has been changed so that the interval between the beam 6b and the information track 2b is set larger than the interval between the beam 6c and the information track 2a. For example, beam 6b
The interval between the beam 6c and the information track 2b is set to about three times the interval between the beam 6c and the information track 2a.

FIG. 19 shows the configuration of the diffraction grating 8 for realizing the beam arrangement shown in FIG. 12. In this embodiment, the same diffraction grating 8 is used during recording and reproduction, and the angle θ is also fixed.

In FIG. 12, beam 6b and track 2b
The distance between the beam 6c and the track 2a is S ₁ , and the distance between the beam 6c and the track 2a is
When S ₂ is set, select so that S ₁ +S ₂ =P and P/2<S ₂ <P. For example, when S ₂ =P/3, S ₁ =2/3P.

Since the spacing S between the beams 6a and 6c in the track pitch direction is S=S ₂ , this is substituted into equation (3) to obtain θ=sin ^-1 (P/3l). If the values of P and l are set as in the previous embodiment, θ=sin ⁻¹ (1.6×10 ⁻³ /3×20×10 ⁻³ ) ≈1.5°. In other words, the diffraction grating 8 is used both during recording and during playback.
The setting angle is θ≒1.5° (clockwise).

FIG. 13 is a graph of light intensity in the case of FIG. 12. In FIG. 4, the vertical positions of the two points 24b and 24c are set equal, but in FIG.
The vertical position (intensity β) of point 4b is set at a predetermined position below that of point 24c (intensity α).

FIG. 14 shows the positional relationship of the beams 6a, 6b, 6c on the disk 1 during reproduction. The positional relationship of each beam 6a, 6b, 6c is the first
Since it is the same as that in Figure 2, the recording beam 6a
In order to scan the information track 2a with the reproduction beam 6a with a reduced intensity, one tracking beam 6b is placed above the reproduction beam 6a and slightly to the right of the information track 2a, and the other tracking beam 6b is placed above the reproduction beam 6a and slightly to the right of the information track 2a. The optical beam 6c is placed below the reproducing beam 6a and slightly to the left of the information track 2a. In Figure 12,
Since the interval between beam 6b and information track 2b is set to three times the interval between beam 6c and information track 2a, in Fig. 14, the interval between beams 6b, 6c and information track 2a is set to 1/4 of the track interval. will be done.

FIG. 15 is a graph of light intensity in the case of FIG. 14. In FIG. 13, the vertical position of the point 24b is set to a predetermined position below that of the point 24c, but in FIG. 15, the vertical positions of the two points 24b and 24c are set to be equal.

As described above, since the vertical position settings of the points 24b and 24c are different between recording and reproduction, the block diagram of the tracking error detection circuit of the optical information recording/reproducing apparatus according to this embodiment is as shown in FIG. do.

That is, the output of the photodetector 15b is input to an amplifier 26 with an amplification factor of α, and the output of the photodetector 15c is input to an amplifier 27 with an amplification factor of β. The outputs of the amplifiers 26 and 27 are input to a differential amplifier 28,
A tracking error detection signal during recording is output. On the other hand, the outputs of the photodetectors 15b and 15c are input to a differential amplifier 29, and a tracking error detection signal during reproduction is output. A switch 30 is provided to switch the tracking error detection signal between recording and reproduction.

A controller 31 that controls the entire apparatus controls the switch 30 to a predetermined setting state during recording and during playback.

As described above, according to the embodiment of the present invention, by switching the tracking error detection signal between recording and reproduction using the circuit, tracking can be performed both during recording and reproduction.

Note that the positional relationship of the beams 6a, 6b, and 6c on the optical disk 1 described in the above embodiment is an example of the present invention, and is not limited thereto. For example, in FIG. 12, the distance between the beam 6b and the information track 2a is set to about three times the distance between the beam 6c and the information track 2a, but it may be set to about twice the distance between the beam 6c and the information track 2a.
In this case, in FIG. 14, the interval between the beams 6b, 6c and the information track 2a is set to 1/3 of the track interval.

〔Effect of the invention〕

As described above, according to the optical information recording and reproducing apparatus of the present invention, the three-beam method, which is the tracking error detection method of the existing optical disc reproducing apparatus, is applied to produce an optical information recording medium that does not have a guide groove. In this method, while tracking an information track on which an information signal has already been recorded, a new information signal can be recorded in an adjacent unrecorded portion with high precision.

[Brief explanation of drawings]

Figure 1 is a front view of the optical disk 1, Figure 2 is a front view of the optical disk 1;
FIG. 0 is a schematic block diagram of an embodiment of the optical information recording/reproducing apparatus based on the present invention, and FIGS. 4, 7, 9, 11, 13
Figure 15 is a graph of the intensity of light reflected on one surface of the optical disk and detected by the photodetector, Figure 17.
18 and 19 are explanatory diagrams showing the setting angle of the diffraction grating, and FIGS. 5 and 16 are block diagrams of the tracking error detection circuit according to the present invention. 1... Optical disk, 2a, 2b... Information track, 5... Semiconductor laser, 6a, 6b, 6c...
Beam, 15a, 15b, 15c...photodetector.

Claims (1)

[Claims] 1. A beam from a light source is divided into a recording beam of the 0th-order diffraction beam and a recording beam of the 1st-order diffraction beam using a diffraction grating.
a tracking beam and a second tracking beam, and use the first and second tracking beams to record first information on an optical information recording medium without a guide groove, on which an information signal has already been recorded. In an optical information recording and reproducing apparatus that forms a second information track by recording an information signal in an unrecorded portion adjacent to the first information track while tracking the first information track, a tracking beam located before the recording beam and between the first information track and the unrecorded portion; and a second tracking beam located after the recording beam and located between the first information track and the unrecorded portion. the recording beam based on the outputs of first and second photodetectors that are disposed between the second information track and the unrecorded area and detect the reflected lights of the first and second tracking beams, respectively; is the second
What is claimed is: 1. An optical information recording/reproducing device, characterized in that the optical information recording/reproducing device is configured to form an information track.