JPH0782657B2 - Optical head device - Google Patents

Description

The present invention relates to an optical head device used for recording / reproducing information on / from an optical information storage medium, and particularly to an optical axis of an information recording / reproducing light beam. The present invention relates to simplification of the configuration of an optical system that detects a relative angle formed by a recording surface of a storage medium.

[Conventional technology]

FIG. 8 (a) is a schematic configuration diagram of a conventional optical head device, and FIG. 8 (b) is a block diagram showing the configuration of the photodetector and its peripheral circuits shown in FIG. 8 (a). . In the figure, 1 is a semiconductor laser (hereinafter referred to as LD) which is a light source,
Reference numeral 3 is a diffraction grating that diffracts the light beam 2 emitted from the LD 1 and splits it into three beams, 4 is a flat beam splitter that reflects the light beam and makes it enter the condenser lens 5, and 6 is a collection of the light rays that have passed through the condenser lens 5. An optical information storage medium (hereinafter referred to as an optical disk) placed near the light spot, 80 is a track composed of a stored information sequence on the disk 6, 27 is an information recording surface on which the track 80 is formed, and 25 is a substrate of the optical disk 6. , 10 are reflected by the optical disc 6, and the condenser lens 5 and the beam splitter 4
Photodetector that receives the light beam 11 that has passed through and photoelectrically converts it, 13,1
2 is a subtractor, 16 is an adder, 18 and 19 are phase compensation circuits, 20 is a focusing actuator for driving the condenser lens 5 in the optical axis direction (± Z), and 21 is the condenser lens 5 which crosses the track 80. A tracking actuator that drives in the direction (± X), and 26 is a motor that rotates the optical disk 6.

Next, the operation of the conventional device will be described. The light flux 2 emitted from the LD1 is diffracted and separated into three light fluxes by the diffraction grating 3, reflected on the surface of the beam splitter 4, and then reflected by the condenser lens 5 through the transparent substrate 25 onto the information recording surface 27 of the optical disc 6 It is condensed as one light spot 9a, 9e, 9f. The line connecting the centers of the three light spots 9a, 9e, 9f is arranged so as to be slightly inclined with respect to the direction of the track 80. The light thus condensed on the information surface of the optical disk 6 is reflected, re-transmitted through the condenser lens 5, and then transmitted through the beam splitter 4 to obtain the astigmatism as is known. It is incident on the detector 10. The photodetector 10 is placed at the position in the optical axis direction where the central beam 11a, that is, the reflected light flux of the 0th-order diffracted light is the circle of least confusion when the focused spot 9a on the optical disk 6 is in the focused state. The photodetector 10 has a six-part configuration as shown in the lower part of the figure
The part that receives 11a is divided into four detection areas A, B, C, and D. Further, the portions that receive the beams 11e and 11f on both sides are independent detectors E and F. As is well known, by subtracting the outputs of the double-sided detectors E and F from E-F by the subtracter 13, the center spot 9a and the track 80 are misaligned in the X direction (tracking error signal V _AT ). Can be detected. The tracking error signal V _AT is applied to the tracking actuator 21 through an appropriate phase compensating circuit 18 to drive the condenser lens 5 in a direction (± X direction) orthogonal to the track 80 so that the spot 9a is correctly positioned at the center of the track 80. Used to correct for position. Further, the output of the central four-divided detector is subjected to a differential operation of the outputs of the diagonal components A, C and B, D with (A + C)-(B + D) by the subtractor 12, thereby defocusing the focused spot 9a ( Focus error V _AF ) can be detected. This defocus detection method is called the astigmatism method, and when the spot on the optical disk 6 is in focus, the spots on the detector, which are in a substantially circular state of the circle of least confusion as shown by 11a, are different from the perspective of the optical disk 6, respectively. According to the defocus of
As shown by the broken line, the elongated elliptical shape in the A, C and B, D directions is converted into an electric output. The focus error signal V _AF is applied to the focusing actuator 20 through an appropriate phase compensation circuit 19 and is used to drive the condenser lens 5 in the optical axis direction (± Z direction) to correct defocus. Further, the sum output V _HF obtained by the adder 16 of the 4-division detector obtained with the rotation of the optical disk 6 is processed and used as a reproduction signal of the optical disk 6 by a circuit (not shown) in the subsequent stage.

In the conventional optical head device, when the recording / reproducing of information is performed through the substrate 25 as described above, the disc information surface 27 has the condensing lens 5 due to the warp of the substrate 25 and the inclination when mounted on the motor 26. Sometimes became non-perpendicular to the optical axis of. Typically, the substrate 25 having a thickness of about 1.25 mm is woven into the lens design together with the condenser lens 5 as one element of the objective lens. However, when the substrate 25 is tilted as described above, coma aberration occurs, and the original recording is performed. / There is a problem that crosstalk from adjacent tracks 81, 82 of the track 80 to be reproduced increases. This phenomenon has been a serious problem that deteriorates the image quality especially in an optical video disc or the like on which analog signals are recorded. In the conventional optical head device, in order to solve the above problems, the verticality between the condenser lens optical axis 40 and the substrate 25 is secured by the tilt servo.

An example of the conventional tilt servo will be described below with reference to FIG.

In the figure, 27 is the information recording surface of the optical disk 6, and 33 is the head housing, which holds the optical system of the optical head device of FIG. 34 is a rotation fulcrum for rotating the head casing 33, 35 is a support member for supporting the rotation fulcrum 34, 36 is a motor, 37
Is a rotating shaft of the motor 36, and is processed into a male screw shape and connected to the head housing 33. Reference numeral 30 denotes a light emitting diode (LED) arranged on the upper surface of the head housing 33, and emits a light beam toward the information recording surface 27 as indicated by an arrow. 3
1, 32 are photodetectors, which are arranged in a row in the X direction (direction orthogonal to the track) with the LED 30 interposed therebetween. 38 is a subtractor, 39 is a phase compensation circuit.

Next, the operation of the conventional tilt servo will be described. LE
The light beam emitted from D30 is reflected by the information recording surface 27,
The light enters the photodetectors 31 and 32 symmetrically arranged on both sides of 30. The outputs of the photodetectors 31 and 32 are output by the subtractor 38 to the photodetector 3
2 output-subtracted as the photodetector 31 output. The amount of light incident on the photodetectors 31 and 32 is set to be equal when the optical axis 40 of the condenser lens 5 shown in FIG. 8 and the substrate 25 are in the vertical state. Therefore, when the substrate 25 is tilted about the Y direction as shown in FIG. 10, the amount of light incident on the photodetectors 31 and 32 becomes unbalanced. Therefore, the output of the subtractor 38 (the output of the tilt sensor) changes between positive and negative depending on the inclination of the substrate 25. The output of the subtractor 38 is applied to the motor 36 via an appropriate phase compensator 39, and the head casing 33 is rotated around the rotation fulcrum 34 according to the rotation of the screw 37. In the conventional optical head device, the optical axis 40 of the condenser lens 5 is kept perpendicular to the substrate 25 by the negative feedback control (tilt servo) as described above.
The generation of coma was minimized to prevent an increase in crosstalk from adjacent tracks.

[Problems to be Solved by the Invention]

As described above, in the conventional optical head device, the light emitted from the LED 30 is received by the pair of photodetectors 31, 32, and the tilt of the optical disk 6 is detected by the operation calculation of the outputs of the photodetectors 31, 32. I got a signal for tilt detection for
Additional optical components such as LED 30 and photo detectors 31, 32 are required,
This will increase the cost. In addition, in the conventional optical head device, there is not so much space between the upper surface of the head housing 33 and the substrate 25, and the arrangement of the LED 30 and the photodetectors 31 and 32 is a great design constraint, and the size is reduced. There was a problem that it was difficult to

The present invention has been made to solve the above-mentioned problems, and a tilt detection signal can be obtained without using an additional optical component for detecting the tilt of an information storage medium (optical disk) as in the related art. It is an object of the present invention to provide an optical head device which can be downsized and reduced in price by obtaining it.

[Means for Solving the Problems]

In the optical head device according to the present invention, the luminous flux emitted from the light source (semiconductor laser 1) is stored in the information storage medium (optical disc 6).
Condensing means (condensing lens 5) for converging and irradiating upward, separating means (beam splitter 4) for separating the reflected light flux from the information storage medium and the emitted light flux, and a first for receiving the reflected light flux. By making a part of the inner surface of the light detecting means (reproducing light detector 10) and the lens barrel (lens barrel 28) holding the light source and the separating means a reflecting surface (lens barrel side surface 29), Of the divergent light beam emitted from the optical system for changing the advancing direction of the unnecessary light beam which is not directly incident on the light converging means to be incident on the light condensing means, and the reflected light beam of the unnecessary light beam from the information storage medium. It is provided with a second light detecting means (tilt detecting light detector 14) for receiving light.

[Action]

The advancing direction changing optical means obtained by using a part of the inner surface of the lens barrel (lens barrel 28) as a reflecting surface (lens barrel side surface 29) is a condensing means (condensing lens) of the light flux emitted from the light source (semiconductor laser 1). 5) The traveling direction of a part of the unnecessary light beams other than the effective light beam incident on 5) is changed and is made incident on the light converging means (the light condensing lens 5). The second light detecting means (tilt detecting light detector 14) receives the reflected light flux of the unnecessary light flux from the information storage medium (optical disk 6), and stores the optical axis of the light focusing means (the condenser lens 5) and the information storage. A signal for detecting the relative angle formed by the information storage surface of the medium (optical disk 6) is output.

Example of Invention

FIG. 1 is a schematic configuration diagram of an optical head device according to a first embodiment of the present invention. In FIG. 1, components corresponding to those shown in FIG. 8 are designated by the same reference numerals, and their description will be omitted. In FIG. 1, 4 is a beam splitter as a separating means for separating the reflected light flux from the optical disc 6 from the outgoing light flux, 7 is an aperture limiting means for limiting the opening of the incident light flux to the condenser lens 5 as the condenser means, Reference numeral 8 denotes an unnecessary light beam (tilt detection light beam) other than the effective light beam 2 which passes through the aperture limiting means 7 and enters the condenser lens 5 among the light beams emitted from the light source LD1, and 14 denotes the unnecessary light beam 8 from the optical disc 6. A tilt detecting photodetector as a second photodetecting means for receiving the reflected light beam of 90, 90 changes the traveling direction of a part of the unnecessary light beam 8 and makes it enter the condenser lens 5 through the aperture limiting means 7. It is a reflection mirror as a traveling direction changing optical means.
The photodetector 14 for tilt detection has detection areas 14a and 14b, and their outputs are given to the subtractor 14A, and the relative angle between the optical axis of the condenser lens 5 and the information storage surface of the optical disk 6, that is, It is used to detect the tilt of the optical disc 6. In addition, the playback / recording mechanism, focus mechanism, and tracking servo mechanism are the same as the conventional ones.
Illustrations of the diffraction grating and the like are omitted.

Next, the tilt detection operation in this embodiment will be described.

In FIG. 1, the luminous flux emitted from the LD1 is a divergent luminous flux having a full width at half maximum of about 10 ° to 40 °, but only a part of the luminous flux (called an effective luminous flux) is used for reproduction / recording. The effective luminous flux 2 is a luminous flux determined by the aperture limit 7 among the divergent luminous fluxes of the LD, and typically has a divergence angle of 10 ° to 15 °. Therefore, other unnecessary light fluxes have not been used conventionally. In the first embodiment, a plane reflection mirror 90 is arranged in this unnecessary light beam, the traveling direction of a part of the unnecessary light beam is changed, and the light passes through the aperture limiting means 7 and is focused on the optical disk 6 by the condenser lens 5. The light spot 17 is irradiated to form the tilt detecting light beam 8. The focused spot 17 is irradiated on a position different from the focused spot 9 for reproduction / recording. Focused spot
The reflected light fluxes from the optical disc 6 of 9 and 17 are imaged at different positions, and are received by the photodetector 10 and the photodetector 14, respectively. The photodetector 14 is for tilt detection, and the detection area
It is a two-part photodetector consisting of 14a and 14b. Optical disc 6
When the vertical axis is perpendicular to the optical axis of the condenser lens 5, the photodetector 14 is arranged so that the light receiving amount of the tilt detecting light beam 8 is equal in the detection region 14a and the detection region 14b. In the figure, when the rotation axis of the optical disk 6 is tilted with respect to the Y axis, the tilt detecting light beam 8 moves in the ± X directions on the photodetector 14. Therefore, the inclination of the optical disc 6 can be detected by performing the calculation process {(14a)-(14b)} for obtaining the difference between the light receiving amount of the detection area 14a and the light receiving amount of the detection area 14b. This tilt information is output as a tilt signal V _TILT from the subtractor 14A. In this way, the tilt detection light beam can be obtained without using a separate light source such as an LED by merely disposing the reflection mirror 90 in the unnecessary light beam of the LD1 which has not been used conventionally.

As a second embodiment, as shown in FIG. 2, two reflecting mirrors 90 facing each other are not limited to one reflecting mirror 90.
-1, 90-2 may be used, and at this time, the unnecessary luminous flux can be used more effectively than in the first embodiment. Light flux for tilt detection is 8
-1, 8-2, and the focused spots 17-1, 17-2 are irradiated on the optical disk 6. Optical detector for tilt detection
14 uses two 2-split detectors, and in FIG. 2, the tilt signal is not shown in the arithmetic processing {(14a) + (14c)} −
It is obtained by {(14b) + (14d)}. That is, the amount of light received by the detection areas 14a, 14c of the photodetector 14 and the detection areas 14b, 1
A tilt signal can be obtained by the difference from the received light amount of 4d.

Next, a third embodiment is shown in FIG. In the first and second embodiments, the tilt detecting light beam 8 is focused on the optical disc 6 and the reflected light beam that has passed through the condenser lens 5 again is detected. However, not all the reflected light flux from the optical disk 6 returns to the condenser lens 5. The tilt detection light beam 8 is
When entering the condenser lens 5 from the LD1, the light is incident with an inclination with respect to the optical axis of the condenser lens 5. Therefore, the tilt detection light beam 8
The optical axis of is reflected by the optical disk 6 as shown in FIG. In the figure, 8'-1 and 8'-2 indicate the optical axes of reflection (0th order reflection) from the optical disk 6. 8'-1,8 '
A reflection mirror 90 is arranged so that the light beam −2 illuminates the flange of the condenser lens 5. The flange of the condenser lens 5 is provided with light detection regions 14a, 14b, 14c and 14d as shown in FIG. 3 (b). Therefore, the arithmetic processing {(14
The tilt signal can be obtained by (a) + (14c)}-{(14b) + (14d)}.

FIG. 4 shows a fourth embodiment. In the third embodiment, the 0th-order diffracted reflected light from the optical disc 6 is detected, but when the information track direction of the optical disc 6 is the Y direction in the figure, the tilt detection light beams 8-1, 8-2 emitted from the LD1 are Although reflected by the optical disk 6, the first-order reflected diffracted light from the information track is diffracted in the X direction. In this embodiment, the primary reflected light 8 ″ -1,8 ″ of the tilt detecting light beams 8-1,8-2 on the optical disk 6 is used.
-2 is detected. At this time, the light detection areas 14a, 14b, 14c, 14d
The tilt detecting photodetector 14 having the above is arranged at a position farther from the condenser lens 5 than in the configuration of the third embodiment.

In the third and fourth embodiments, the 0th-order reflected light 8 ′ and the 1st-order reflected light 8 ″ from the optical disk 6 are divergent light fluxes and become large irradiation spots on the tilt detecting photodetector 14. Tilt detection In order to efficiently receive the light beam 8 for light, the irradiation light beam is preferably smaller than the detection region of the photodetector 14. The irradiation spot 17 of the light beam 8 for tilt detection on the optical disk 6 is not in a condensed state. For example, a collimated light beam may be used.To realize this, the reflection mirror 90 may be a curved surface such as a convex reflection mirror instead of a flat surface.At this time, the reflected light beam from the optical disk 6 may be a collimated light beam. The reflected light flux can be efficiently received by the photodetector 14.

Further, the outgoing light flux 2 used for reproduction / recording should have substantially no aberration in order to obtain good reproduction / recording characteristics. However, the tilt detection light beam 8 does not affect the tilt detection characteristics even if there is some aberration. Therefore, the reflection mirror 90 does not need to be subjected to expensive optical polishing, and an inexpensive glass plate may be used. Further, the reflection mirror 90 may be a plastic plate or thin aluminum paper. Further, without using the above-mentioned parts for performing reflection, for example, one surface of the lens barrel to which the LD1, the beam splitter (half mirror) 4 and the like are attached may be polished so that the light flux can be reflected. .

FIG. 5 shows a configuration example of the lens barrel 28. In this example, the lens barrel side surface 29 between the LD1 and the half mirror 4 is formed in a flat shape, and the divergent light flux from the LD1 is polished so as to reflect the light flux 8 which hits the side surface 29. Such a lens barrel 28 can be applied to the first to fourth embodiments.

Further, in the first and second embodiments, the photodetectors 10 and 14 are separately arranged. This is because it was necessary to adjust the position of the two-divided photodetector 14 independently of the reproduction detector 10. That is, when the optical disc 6 is perpendicular to the optical axis of the condenser lens 5, the reflected light of the light beam 8 for tilt detection from the optical disc 6 is irradiated onto the dividing line of the two-divided detector, and the detection area 14a and the detection area 14b are formed. Had to be adjusted so that their outputs were equal.

Therefore, a semiconductor position detecting element (Posi
If a photosensitivity detector (PSD) 15 is used as a sensor for receiving the tilt detection light beam 8, it is not necessary to perform position adjustment, and a photodetector 17 integrated with the reproduction photodetector 10 can be configured. FIG. 6 shows the structure of the photodetector 17 in which the PSD 15 and the reproduction photodetector 10 are integrated.

A case where the photodetector 17 is applied to the first embodiment will be described. The PSD 15 detects the irradiation position of the light spot 8 in the X direction, and uses the currents ia and ib flowing at both ends of the PSD 15 to output (ia-ib) / (ia + ib) as a position signal by the arithmetic unit 50, for example.
Output as 51. In this case, the position signal 51 is known to be proportional to the displacement of the spot center of gravity from the center of the PSD 15. Therefore, if the position signal 51 is used, the split detector 14
Similarly, the tilt signal can be obtained. However PSD15
Since PSD and detector 11 are integrated, PSD15 cannot be adjusted independently. PSD15 is ia when the center is illuminated
= Ib, and the position signal 51, which is the calculation output, becomes zero. The light spot 8 may not be irradiated to the center when the optical disc 6 is not tilted, and at this time, ia ≠ ib, and an offset occurs in the tilt signal.

Therefore, the arithmetic unit 50 as shown in FIG. 7 may be configured. The arithmetic unit 50 has an offset adjusting circuit 52 and outputs (ia-ib + δ) / (ia + ib) as the position signal 51. The offset δ may be adjusted by the offset adjusting circuit 52 so that the position signal 51 becomes zero when the optical disk 6 is not tilted, and the position of the PSD 15 does not have to be adjusted independently. In FIG. 7, the operational amplifier 53 is r (ia-ib + δ).
And the operational amplifier 54 outputs r (ia + ib). Further, the position signal output circuit 55 outputs the position signal 51.

According to the above-described embodiment, the reproduction / reproduction of the light flux emitted from the LD is performed.
By using an unnecessary light beam other than the effective light beam used for recording as a light beam for the tilt sensor, changing the traveling direction of the unnecessary light beam and making it enter the condenser lens, the tilt sensor is placed at a position different from the reproduction / recording spot on the optical disc. Since the use light beam is emitted, the light beam for tilt detection can be obtained without using another light source such as an LED as in the conventional case, and the tilt of the optical disc can be detected.

〔The invention's effect〕

As described above, according to the present invention, a condensing unit that condenses and irradiates the light flux emitted from the light source onto the information storage medium, a separating unit that separates the reflected light flux from the information storage medium from the emission light flux, The first light detecting means for receiving the reflected light flux and a part of the inner surface of the lens barrel holding the light source and the separating means are made into a reflecting surface, so that the condensing means of the divergent light flux emitted from the light source. A traveling direction changing optical unit that changes the traveling direction of the unnecessary light beam that is directly incident on the light-collecting unit, and a second light detection unit that receives the reflected light beam of the unnecessary light beam from the information storage medium. Therefore, it is possible to generate a tilt detection light beam without using an additional optical component for detecting the tilt of the information storage medium as in the conventional case, and thus it is possible to obtain a tilt detection signal. The number of points decreases Together also simplifies configuration, there is an advantage that it is possible to reduce the size and cost reduction.

[Brief description of drawings]

1 is a schematic configuration diagram of an optical head device according to a first embodiment of the present invention, FIG. 2 is a schematic configuration diagram of an optical head device according to a second embodiment, FIG. 3 (a), (B) is a schematic configuration diagram of the optical head device according to the third embodiment, FIG. 4 is a schematic configuration diagram of the optical head device according to the fourth embodiment, and FIG. 5 is applicable to the above embodiment. 6 is a block diagram of a lens barrel, FIG. 6 is a block diagram of a photodetector applicable to the above embodiment, FIG. 7 is an electric circuit diagram of the arithmetic unit of FIG. 6, and FIG. 8A is a conventional optical head. FIG. 8B is a schematic block diagram of the device, FIG. 8B is a block diagram showing the configuration of the photodetector and its peripheral circuit in FIG. 8A, and FIGS. 9 and 10 are schematic configuration diagrams of a conventional tilt servo mechanism. . 1 ... LD (light source), 4 ... Beam splitter (separating means), 5 ... Condensing lens (condensing means), 6 ... Optical disk (information storage medium), 10 ... Playback photodetector (first) 1) optical detecting means), 14 ... optical detector for tilt detection (second optical detecting means), 15 ... semiconductor position detecting element, 28 ... barrel, 9
0,90-1, 90-2 ... Reflecting mirror (traveling direction changing optical means).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Saito 1 Baba Institute, Nagaokakyo City, Kyoto Prefecture Mitsubishi Electric Co., Ltd. Electronic Product Development Laboratory (72) Manabu Koike 1 Baba Institute, Nagaoka Kyoto Prefecture Mitsubishi Electric Electronic Product Development Laboratory Co., Ltd. (56) Reference JP-A-60-1632 (JP, A) JP-A-59-152529 (JP, A) Actually developed Shou 62-22726 (JP, U)

Claims (2)

[Claims] 1. A condensing means for condensing and irradiating a light beam emitted from a light source onto an information storage medium, a separating means for separating a reflected light beam from the information storage medium from the emitted light beam, and receiving the reflected light beam. By making a part of the inner surface of the lens barrel holding the first light detecting means and the light source and the separating means a reflecting surface, it is not necessary to directly enter the condensing means out of the divergent light flux emitted from the light source. A traveling direction changing optical means for changing the traveling direction of the light flux to enter the light collecting means, and a second light detecting means for receiving the reflected light flux of the unnecessary light flux from the information storage medium are provided. Optical head device. 2. The optical head device according to claim 1, wherein the second light detecting means is arranged close to the first light detecting means.