JP2015144029A - Sub beam position adjustment method of optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-laser beam optical pickup device which allows a diffraction grating to be more accurately adjusted and reduces workload of an operator.SOLUTION: A sub beam position adjustment method includes: irradiating an adjustment disk having a first region including a larger track pitch than that of DVD with a main beam and a sub beam (S1, S2); a first light-receiving step of receiving an output signal obtained by a first light reception unit receiving reproduction light from the first region in the main beam, and an output signal obtained by a second light reception unit receiving reproduction light from the first region in any sub beam; and a first adjustment step (S3) of adjusting the position of a diffraction grating on the basis of variations of a phase difference between the output signal from the first light reception unit and the output signal from the second light reception unit.

Description

  The present invention relates to a sub-beam position adjusting method for an optical pickup that generates a main beam and a sub-beam by using a diffraction grating for light emitted from a light source.

  2. Description of the Related Art Conventionally, an optical pickup device that reads information by irradiating an optical disk such as a DVD (Digital Versatile Disk) with light from a light source is known. In the optical pickup device, the light from the light source is condensed on the optical disk through the objective lens, and the reflected information (reproduction light) from the optical disk is received by the light receiving unit, thereby reading the recorded information. In addition, a track is formed in a spiral shape on the optical disc, and the optical pickup device performs tracking control so that a light collecting position (hereinafter also referred to as a spot) follows the track.

As a tracking control method of the optical pickup device, a three-laser beam method using a main beam and sub beams (first sub beam and second sub beam) is known. FIG. 9 is a diagram for explaining a conventional three-laser beam method. As shown in FIG. 9A, the main beam MB is arranged in the middle, and two sub beams SB are arranged on both sides thereof. Here, the first sub beam SB1 converges at a position preceding the main beam MB along the scanning direction of the optical head with respect to the optical disc. The second sub-beam SB2 converges at a position following the main beam M along the scanning direction of the optical head with respect to the optical disc.
In FIG. 9A, the main beam MB is directly above the track T, which shows the most preferable state. In this state, both of the sub beams SB1 and SB2 are slightly over the adjacent track T, and the subsequent spot area is on a so-called mirror surface without pits. (Not shown).

When the light receiving unit receives the reproduction light, the light receiving unit outputs an output signal corresponding to the amount of light received. In the example of FIG. 9A, output signals corresponding to the sub beams SB1 and SB2 output from the light receiving unit are output to the differential amplifier. Here, in Fig.9 (a), the condensing position of each beam in the case of condensing sub-beam SB1 to an outer peripheral side is shown as a continuous line. Further, the condensing position of each beam when the sub beam SB1 is condensed on the inner peripheral side is indicated by a solid line. In FIG. 9A, the amount of light received by the light receiving portions that receive the sub beams SB1 and SB2 is equal, and therefore the signal from the differential amplifier (sub tracking error signal) is zero.
Further, when the position of the spot slightly moves from now on, a differential signal between the sub beam SB1 and the sub beam SB2 is output from the differential amplifier. That is, by the three-laser beam method, information on which side of one track the focal position of the main beam MB is shifted and information on the shift amount of the main beam MB are obtained.

  In order to generate these three beams, conventionally, light from a light source is diffracted by a diffraction grating, and a main beam of zero-order light (without diffraction), a first sub-beam of plus first-order light, and minus one And a second sub-beam of the next light. Based on the light from the light source by the diffraction grating, a main beam and a first sub beam SB1 and a second sub beam SB2 that are collected in a diagonal direction with the main beam as a center are generated. Therefore, by adjusting the position of the diffraction grating, it is possible to adjust the condensing positions of the main beam MB and the sub beams SB1 and SB1.

  The position adjustment of the diffraction grating is performed as follows. First, with the servo for tracking control turned off, the main beam and the sub beam are condensed on the optical disc, and an output signal is output from the light receiving unit. Next, the position of the diffraction grating is adjusted based on the waveform change of the output signal that is output (see, for example, Patent Document 1).

In addition, the position of the preceding first sub beam SB1 may be focused on the inner peripheral side of the optical disc or may be focused on the outer peripheral side. FIG. 9B shows a change in the output signal when the main beam MB is focused on the optical disk and traversed across the track of the optical disk. FIG. 9C shows the change in the output signal when the first sub beam SB1 is focused on the outer peripheral side of the optical disc and traversed across the track. FIG. 9D shows a change in the output signal when the first sub beam SB1 is focused on the inner circumference side of the optical disk and traversed across the track. As shown in FIGS. 9B to 9D, the output signal when the first sub beam SB1 is condensed on the inner peripheral side and the output signal when the first sub beam SB1 is condensed on the outer peripheral side have the same phase. . Therefore, the condensing position of the first sub beam SB1 cannot be adjusted to the inner peripheral side or the outer peripheral side based on the waveform change of the output signal.
For this reason, conventionally, in order to adjust the condensing position of the first sub-beam SB1, the operator performs the adjustment while rotating the diffraction grating (see, for example, Patent Document 2).

JP 2006-147066 A JP 2011-108322 A

  However, since there is no adjustment index in the conventional adjustment method, a poorly adjusted product is likely to flow out in the subsequent process, and the work load required for adjustment is high.

  The present invention has been made in view of the above problems, and it is an object of the present invention to make it possible to adjust the position of a sub beam with higher accuracy and to reduce the work load of an operator in a three-laser beam type optical pickup device.

Application example 1
In order to solve the above-described problem, in one embodiment of the present invention, light emitted from a light source is diffracted using a diffraction grating, and a main beam and two diagonal positions centered on the main beam are positioned. A sub-beam position adjustment method for an optical pickup that generates a sub-beam, collects the main beam and the sub-beam on a track on a DVD by an objective lens, and reads information from the DVD, and includes a track pitch of the DVD An adjustment disk having a first region with a larger track pitch is irradiated with the main beam and the sub beam, and the reproduction light from the first region in the main beam is received by a first light receiving unit. An output signal and an output signal obtained by receiving the reproduction light from the first region in any one of the sub beams by the second light receiving unit are acquired. A first adjustment that adjusts the position of the diffraction grating based on a phase difference between a first light receiving step, an output signal from the first light receiving unit, and an output signal from the second light receiving unit. Steps.

In the invention configured as described above, the reproduction light from the first region having a track pitch larger than the track pitch of the DVD is received by the first light receiving unit and the second light receiving unit and output from the respective light receiving units. Get the output signal. Then, the diffraction grating is adjusted based on the phase difference between the output signals from the first light receiving unit and the second light receiving unit.
For this reason, when the sub-beam focusing position is set to the inner or outer peripheral side, the position of the sub-beam can be adjusted more accurately by moving the diffraction grating based on the phase difference, and the work load on the operator can be reduced. Can do.

Application example 2
In one aspect of the present invention, the track pitch of the first region is about twice as large as the track pitch of the DVD.
In the invention configured as described above, since a CD track pitch (1.6 micrometers) can be used for a DVD track pitch (0.74 micrometers), a conventional manufacturing apparatus is used. Thus, the adjustment disk having the first region can be manufactured.

Application example 3
In one aspect of the present invention, in the first adjustment step, an output signal from a light receiving unit that has received the first reproduction light and an output signal from a light reception unit that has received the second reproduction light. The position of the diffraction grating is adjusted so that the phase difference is 90 degrees.
In the invention configured as described above, the present invention can be applied even when the condensing position of the sub beam advances by 90 degrees with respect to the condensing position of the main beam.

Application example 4
In one aspect of the present invention, the adjustment disk has a second area having the same track pitch as that of the DVD, the main area and the sub beam are irradiated to the second area, and the main beam An output signal obtained by receiving the reproduction light from the second region in the first light receiving unit and an output signal obtained by receiving the reproduction light from the second region in the sub beam by the second light receiving unit. A position of the diffraction grating based on a variation in phase difference between a second light receiving step for obtaining a signal, an output signal from the first light receiving unit, and an output signal from the second light receiving unit. A second adjusting step for adjusting.
In the invention configured as described above, the position of the diffraction grating can be adjusted more accurately because the condensing position of the main beam and the sub beam is adjusted after adjusting the condensing position of the sub beam.

The block diagram which shows the structure of the apparatus used for adjustment of an optical pick-up. 1 is a diagram illustrating an optical system provided in an optical pickup device 1. FIG. The figure which shows the diffraction grating 31 fixed to the chassis of the pickup 3. FIG. The figure which shows the structure of the disk 50 for adjustment. The flowchart explaining the adjustment method of a diffraction grating. The figure which shows the relationship between the condensing position of a spot, and the output signal from a light-receiving part. The figure which shows the relationship between the condensing position of a spot, and the output signal from a light-receiving part. 9 is a flowchart showing a method for adjusting a diffraction grating 31 in the second embodiment. The figure explaining the 3 laser beam method which is a prior art example.

Hereinafter, embodiments of the present invention will be described in the following order.
1. First embodiment:
(1) Configuration of apparatus used for adjustment of optical pickup (2) Adjustment method of optical pickup Second embodiment:
3. Third embodiment:
4). Other embodiments:

1. First embodiment:
(1) Configuration of Device Used for Adjustment of Optical Pickup FIG. 1 is a block diagram showing a configuration of a device used for adjustment of an optical pickup. FIG. 2 is a diagram showing an optical system provided in the optical pickup device 1. In the first embodiment, the adjustment jig 10 and the adjustment disk 50 are used to adjust the diffraction grating included in the optical pickup device 1.

First, the configuration of the optical pickup device 1 will be described.
As shown in FIG. 1, the optical pickup device 1 includes an optical pickup 3, a light receiving unit 4, a signal calculator 5, a digital servo processor 6, a tracking actuator 7, and a focus actuator 8. The optical pickup device 1 can reproduce and record a DVD (Digital Versatical Disk) as a medium.

  As shown in FIG. 2, the optical pickup 3 includes a semiconductor laser 2 that emits light and an optical component 30 that serves as an optical path of the light emitted from the semiconductor laser 2. The optical component 30 includes a diffraction grating 31, a beam splitter 32, a quarter wavelength plate 33, a collimator lens 34, a reflection mirror 35, an objective lens 36, and a cylindrical lens 37.

  Laser light emitted from the semiconductor laser 2 is divided into a main beam MB and sub beams (first sub beam SB1 and second sub beam SB2) by the diffraction grating 31. Laser light (main beam, sub beam) that has passed through the diffraction grating 31 is reflected by the beam splitter 32 and passes through the quarter-wave plate 33 and the collimating lens 34. The laser light transmitted through the collimator lens 34 is reflected at a predetermined angle by the reflection mirror 35 and reaches the objective lens 36.

  The objective lens 36 condenses the incident laser light on the information recording layer of the medium. Then, the laser beam condensed on the medium is reflected by the information recording layer and becomes reproduction light. The reproduction light passes through the objective lens 36, is reflected by the reflection mirror 35, and passes through the collimating lens 34, the quarter wavelength plate 33, and the beam splitter 32 in this order. Then, the reproduction light transmitted through the beam splitter 32 is given astigmatism by the cylindrical lens 37 and is condensed on the light receiving unit 4.

  The light receiving unit 4 converts the received reproduction light into a current, and outputs a signal for reading data from the optical disc, an output signal for detecting a focus error, and an output signal for detecting a tracking error. As shown in FIG. 1, the light receiving unit 4 includes a main detection unit (first light reception unit) 41 and sub detection units (sub detection units) 42 and 43. The main detection unit 41 is a surface that receives reproduction light based on the main beam MB. The sub detectors 42 and 43 are surfaces on which reproduction light based on the first sub beam SB1 and the second sub beam SB2 is received.

  The signal calculator 5 generates a tracking error signal and a focus error signal from the output signals output from the light receiving unit 4. The tracking error signal and the focus error signal are input from the signal calculator 5 to the digital servo processor 6.

  The digital servo processor 6 controls the tracking actuator 7 that drives the optical pickup 3 so that the optical pickup 3 follows the track of the optical disc in accordance with the tracking error signal. Further, the digital servo processor 6 controls the focus actuator 8 so that the distance between the objective lens (reference numeral 36 in FIG. 2) provided in the optical pickup 3 and the optical disk is appropriate.

Next, the diffraction grating 31 will be described.
FIG. 3 is a view showing the diffraction grating 31 fixed to the chassis of the optical pickup 3.
As shown in FIG. 3A, the diffraction grating 31 is rotatably positioned on the chassis 20 of the optical pickup 3 along the optical axis via the GRT holder 21. Further, the GRT holder 21 is formed with a concave groove 22 for rotating the GRT holder 21.
When the operator rotates the diffraction grating 31 in the directions of arrows a and b in the drawing, first, the tip of the operation shaft 23 is inserted into the concave groove 22. The distal end of the operation shaft 23 is an eccentric shaft and is fitted into the concave groove 22. Then, the operator rotates the operation shaft 23 to rotate the diffraction grating 31 together with the GRT holder 21 in the directions of arrows a and b.

  Then, as shown in FIG. 3B, when the position adjustment of the diffraction grating 31 is completed, the ultraviolet curable adhesive UV is applied to the concave groove 22. Then, the GRT holder 21 is fixed to the chassis 20 by irradiating ultraviolet rays to cure the ultraviolet curable adhesive UV.

  Next, the adjustment jig 10 will be described. As shown in FIG. 1, the adjustment jig 10 includes a phase difference detection unit 11 and a computer device 12.

The phase difference detection unit 11 calculates the phase difference between the output signal from the main detection unit 41 of the light receiving unit 4 and the output signal from the sub detection unit 42, and outputs it to the computer apparatus 12. For example, the phase difference detection unit 11 samples the output signal at a predetermined period and calculates the phase difference.
The phase difference detection unit 11 may be realized by a part of the signal calculator 5 in addition to being a part of the adjustment jig 10.

  The computer device 12 controls the driving of the adjustment jig 10 in an integrated manner. Specifically, the computer device 12 causes the optical pickup device 1 to reproduce the adjustment disk 50 and displays the phase difference between the output signals from the main detection unit 41 and the sub detection unit 42 calculated by the phase difference detection unit 11 on the screen. To display.

Next, the adjustment disk 50 will be described.
FIG. 4 is a diagram showing the configuration of the adjustment disk 50. The adjustment disk 50 has a first area 51 and a second area 52 formed on different information recording layers. The track pitch P1 of the first region 51 is larger than the track pitch P2 of the second region 52. For example, the track pitch P1 of the first region 51 is twice the track pitch P2 of the second region 52. In FIG. 4, the hatched portion is a track.

  In the first area 51, tracks are formed in a spiral shape from the outer periphery to the inner periphery of the adjustment disk 50. As shown in FIG. 4B, the track pitch P1 of the tracks formed in the first region 51 is 1.6 micrometers.

  In the second region 52, tracks are formed in a spiral shape from the outer periphery to the inner periphery of the adjustment disk 50. As shown in FIG. 4C, the track pitch P2 of the tracks formed in the second region 52 is 0.74 micrometers (μm). The track pitch P2 of the second region 52 is the same as the track pitch of the DVD that is the recording / reproducing target of the optical pickup device 1.

(2) Optical Pickup Adjustment Method Next, an optical pickup adjustment method will be described.
FIG. 5 is a flowchart for explaining a method for adjusting a diffraction grating. 6 and 7 are diagrams showing the relationship between the spot condensing position and the output signal from the light receiving unit.

  In the adjustment method shown in FIG. 5, steps S1 to S2 are the first light receiving step of the present invention. Step S3 is the first adjustment step of the present invention. Steps S4 to S5 are the second light receiving step of the present invention. Further, step S6 is a second adjustment step of the present invention.

  In step S <b> 1, the computer device 12 causes the optical pickup device 1 to seek the first area 51 of the adjustment disk 50. As described above, in the first region 51, the track pitch P1 is 1.6 μm. Hereinafter, a spot focused on the adjustment disk 50 by the main beam is also referred to as a main spot MS, and a spot focused on the adjustment disk 50 by the first sub beam is also referred to as a sub spot SS.

  In step S <b> 2, the computer device 12 causes the optical pickup device 1 to reproduce the first area 51 of the adjustment disk 50 with the tracking actuator 7 turned off. Since the tracking servo is turned off, the main spot MS and the sub spot SP collected through the objective lens 36 cross the tracks in the first region 51 without following them. Therefore, the light receiving unit 4 outputs to the phase difference detecting unit 11 an output signal whose amplitude changes according to a change in the amount of received light when the main spot MS and the sub spot SS cross the track.

FIG. 6A is a diagram illustrating a change in the amount of light received by the light receiving unit 4 when the first sub beam SB1 is focused on the inner peripheral side of the adjustment disk 50. FIG. As shown in FIG. 6A, the timing at which the main beam MB and the first sub beam SB1 cross the track T changes due to the difference in the condensing position on the adjustment disk 50 between the main beam MB and the first sub beam SB1. The output signal output from the main detection unit 41 and the output signal output from the sub detection unit 42 are shifted in phase.
As shown in FIG. 6B, when the first sub beam SB1 is focused on the inner circumference side of the adjustment disk 50, the output signal output from the sub detection unit 42 is the output output from the main detection unit 41. The waveform is 90 degrees out of phase with respect to the signal.

FIG. 7A is a diagram illustrating a change in the amount of light received by the light receiving unit 4 when the first sub beam SB1 is condensed on the outer peripheral side of the adjustment disk 50. FIG. Even when the first sub beam SB1 is condensed on the outer peripheral side of the adjustment disk 50, as shown in FIG. 7A, due to the difference in the condensing position on the adjustment disk 50 between the main beam MB and the first sub beam SB1, A phase shift occurs between the output signal output from the main detection unit 41 and the output signal output from the sub detection unit 42.
As shown in FIG. 7B, when the first sub beam SB1 is focused on the outer peripheral side of the adjustment disk 50, the output signal output from the sub detection unit 42 is the output signal output from the main detection unit 41. On the other hand, the waveform has a phase advanced by 90 degrees.

  Therefore, the phase difference detection unit 11 digitizes the phase difference between the output signal from the main detection unit 41 and the output signal from the sub detection unit 42 and outputs the numerical value to the computer device 12.

  In step S <b> 3, the operator adjusts the diffraction grating 31 while confirming the phase difference displayed on the screen of the computer device 12. In this step S3, the position (inner peripheral side, outer peripheral side) where the first sub beam SB1 is focused is adjusted. Specifically, as shown in FIG. 3A, by rotating the operating shaft 23 and rotating the diffraction grating 31 together with the GRT holder 21, the focusing position (spot) of the main beam MB is set as the center. The sub-beam focusing position (spot) changes. Therefore, the operator confirms the phase difference displayed on the computer device 12, and the phase difference displayed on the screen becomes plus 90 degrees or minus 90 degrees depending on the position where the first sub beam SB1 is focused. The position of the diffraction grating 31 is adjusted.

As described above, when the condensing position of the first sub-beam SB1 is adjusted, the main beam MB and the sub-beams SB1 and SB2 are next used by using the track pitch P2 of the DVD to be reproduced / recorded by the optical pickup device 1. Adjust the condensing position relationship.
Therefore, in step S4, the computer device 12 causes the optical pickup device 1 to seek the second area 52. As described above, the second region 52 has a track pitch P2 of 0.74 μm and a DVD track pitch P2 to be reproduced by the optical pickup device 1.

  In step S5, the second area 52 of the adjustment disk 50 is reproduced with the tracking servo turned off. Since the tracking servo is OFF, the main beam MB and the sub beam SB traverse the track of the adjustment disk 50 without following. Therefore, the light receiving unit 4 outputs to the phase difference detecting unit 11 a detection signal whose amplitude changes according to a change in the amount of received light when the main spot MS and the sub spot SS cross the track.

  In step S <b> 6, the operator adjusts the diffraction grating 31 as shown in FIG. 3A while checking the phase difference displayed on the screen of the computer device 12. In step S6, the diffraction grating 31 is adjusted so that the phase difference between the output signal output from the main detection unit 41 and the output signal output from the sub detection unit 42 is 180 degrees.

  Thereafter, when the adjustment of the diffraction grating 31 is completed, the GRT holder 21 to which the diffraction grating 31 is fixed is fixed to the chassis 20. That is, as shown in FIG. 3B, the GRT holder 21 is fixed to the chassis 20 with the ultraviolet curable adhesive UV.

  As described above, in the first embodiment, when adjusting the position of the diffraction grating 31 in order to adjust the position (inner peripheral side, outer peripheral side) of the first sub beam SB1, adjustment is performed based on the phase difference. Therefore, the position of the sub beam can be adjusted with higher accuracy, and the work load on the operator can be reduced.

2. Second embodiment:
FIG. 8 is a flowchart showing a method for adjusting the diffraction grating 31 in the second embodiment. Also in the flowchart shown in FIG. 8, the diffraction grating 31 is adjusted.

  In step S <b> 11, the computer apparatus 12 causes the optical pickup apparatus 1 to seek the first area 51 of the adjustment disk 50. As in the first embodiment, the first region 51 has a track pitch P1 of 1.6 μm.

  In step S <b> 12, the computer device 12 causes the optical pickup device 1 to reproduce the first area 51 of the adjustment disk 50 with the tracking actuator 7 turned off.

  In step S <b> 13, the operator adjusts the diffraction grating 31 while confirming the phase difference displayed on the screen of the computer device 12. In step S13, the condensing position (inner periphery side, outer periphery side) of the first sub beam SB1 on the adjustment disk 50 is adjusted.

  In step S14, the second area 52 is sought for the optical pickup device 1. Also in the second embodiment, the second region 52 has a track pitch P2 of 0.74 μm, which is the same as the track pitch of DVD.

  In step S15, the second area 52 of the adjustment disk 50 is reproduced with the tracking servo turned off. The computer device 12 displays the phase difference between the output signal from the main detection unit 41 and the output signal from the sub detection unit 42.

  In step S <b> 16, the operator adjusts the diffraction grating 31 while checking the phase difference displayed on the screen of the computer device 12. That is, the diffraction grating 31 is adjusted so that the phase difference between the output signal from the main detection unit 41 and the output signal from the sub detection unit 42 is 180 degrees. In step S16, the diffraction grating 31 is adjusted based on the track pitch of the DVD.

  If the adjustment result is NG in step S17 (step S17: NO), the process returns to step S11. That is, the adjustment of the diffraction grating 31 for adjusting the position of the first sub beam SB1 is executed again (steps S11 to S16).

Hereinafter, if the adjustment result is OK in step S17 (step S17: YES), the adjustment of the diffraction grating 31 is terminated.
When the adjustment of the position of the diffraction grating 31 is completed, the GRT holder 21 is fixed to the chassis 20 as shown in FIG.

  As described above, in the second embodiment, if the adjustment result is NG, the diffraction grating 31 is further finely adjusted, so that the position of the sub beam can be adjusted with high accuracy.

3. Third embodiment:
Further, the number of track pitches to be reproduced by the optical pickup device 1 in order to adjust the position of the diffraction grating 31 is not limited to two. In the adjustment of the diffraction grating for adjusting the condensing position of the first sub beam SB1, three track pitches are used in which the track pitch is changed to the plus side and the minus side around the track pitch of 1.6 micrometers. Thus, the position of the diffraction grating 31 may be adjusted.

  That is, first, the phase difference between the output signal from the main detection unit 41 and the output signal from the sub detection unit 42 using the adjustment jig 10 and the track pitch of 1.4 micrometers of the adjustment disk 50. The diffraction grating 31 is adjusted so that becomes a desired one. Next, with the adjustment jig 10, the phase difference between the output signal from the main detection unit 41 and the output signal from the sub detection unit 42 is obtained using a track pitch of 1.8 μm of the adjustment disk 50. The diffraction grating 31 is adjusted so that it becomes a desired one. Finally, with the adjustment jig 10, the phase difference between the output signal from the main detection unit 41 and the output signal from the sub detection unit 42 is obtained using a track pitch of 1.6 μm of the adjustment disk 50. The diffraction grating 31 is adjusted so that it becomes a desired one.

  As described above, in the third embodiment, since the position of the diffraction grating 31 is adjusted using a plurality of track pitches, the condensing position of the first sub beam SB1 can be adjusted with higher accuracy.

4). Other embodiments:
Further, the adjustment of the diffraction grating 31 may be performed only by using the track pitch of the first region 51.
With the above configuration, the time required for adjustment can be shortened.

Needless to say, the present invention is not limited to the above embodiments. It goes without saying for those skilled in the art,
・ Applying mutually interchangeable members and configurations disclosed in the above embodiments by appropriately changing the combination thereof.− Although not disclosed in the above embodiments, it is a publicly known technique and the above embodiments. The members and configurations that can be mutually replaced with the members and configurations disclosed in the above are appropriately replaced, and the combination is changed and applied. It is an embodiment of the present invention that a person skilled in the art can appropriately replace the members and configurations that can be assumed as substitutes for the members and configurations disclosed in the above-described embodiments, and change the combinations and apply them. It is disclosed as.

  DESCRIPTION OF SYMBOLS 1 ... Optical pick-up apparatus, 2 ... Semiconductor laser, 3 ... Optical pick-up, 4 ... Light-receiving part, 5 ... Signal computing unit, 6 ... Digital servo processor, 7 ... Tracking actuator, 8 ... Focus actuator, 10 ... Adjustment jig, DESCRIPTION OF SYMBOLS 11 ... Phase difference detection part, 12 ... Computer apparatus, 20 ... Chassis, 21 ... GRT holder, 22 ... Groove, 23 ... Operation axis, 30 ... Optical component, 31 ... Diffraction grating, 32 ... Beam splitter, 33 ... 1 / 4 wavelength plate, 34 ... collimating lens, 35 ... reflection mirror, 36 ... objective lens, 37 ... cylindrical lens, 41 ... main detection unit, 42, 43 ... sub detection unit, 50 ... adjustment disk, 51 ... first area, 52 ... 2nd area

Claims (4)

The light emitted from the light source is diffracted using a diffraction grating to generate a main beam and two sub-beams located diagonally about the main beam, and the main lens and the sub-beam are generated by an objective lens. Is a method of adjusting the sub-beam position of an optical pickup that reads information from the DVD by focusing the light on a track on the DVD,
An adjustment disk having a first area having a track pitch larger than the track pitch of the DVD is irradiated with the main beam and the sub beam, and reproduction light from the first area in the main beam is emitted to a first light receiving unit. A first light receiving step for obtaining an output signal obtained by receiving the output light, and an output signal obtained by receiving the reproduction light from the first region in any one of the sub beams by the second light receiving unit;
And a first adjustment step for adjusting the position of the diffraction grating based on a variation in the phase difference between the output signal from the first light receiving unit and the output signal from the second light receiving unit. A sub-beam position adjusting method for an optical pickup as a feature.   2. The method of claim 1, wherein the track pitch of the first area is about twice as large as the track pitch of the DVD.   Adjusting the position of the diffraction grating so that the phase difference between the output signal from the first light receiving unit and the output signal from the second light receiving unit is 90 degrees in the first adjustment step; 3. The sub-beam position adjusting method for an optical pickup according to claim 1, wherein the sub-beam position is adjusted. The adjustment disk has a second area having the same track pitch as that of the DVD,
An output signal obtained by irradiating the second region with the main beam and the sub beam, and receiving reproduction light from the second region in the main beam by the first light receiving unit, and the second signal in the sub beam. A second light receiving step for obtaining an output signal obtained by receiving the reproduction light from the region with the second light receiving unit;
And a second adjustment step of adjusting the position of the diffraction grating based on a variation in phase difference between the output signal from the first light receiving unit and the output signal from the second light receiving unit. 4. The sub-beam position adjusting method for an optical pickup according to claim 1, wherein the sub-beam position is adjusted.

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