JP2005085394A - Inspection apparatus and inspection method for optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection apparatus for an optical pickup which is utilized at the time of adjusting three light beam positions by rotating the grating of the optical pickup and which can adjust the positions of the three light spots to normal positions even when pulsation exists at the intensity level on the reference side of photodetection signals. <P>SOLUTION: The inspection apparatus for the optical pickup has a reproduction signal observation device which is inputted with the photodetection signals from two photodetectors 39a and 39c among the three photodetectors 39a to 39c for receiving the reflected light from an optical disk by the three light beams. The reproduction signal observation device is equipped with noise removal circuits 52 and 63 for removing the pulsation on the reference level side in the inputted two signals, low-pass filters 53 and 64 for subjecting the two signals removed of the pulsation to the low-pass filter processing and a phase meter for measuring the phase difference of the two signals subjected to the low-pass filter processing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inspection apparatus and an inspection method for an optical pickup that are used when three optical spots are formed on an optical disk by a grating (diffraction grating) and the optical pickup is adjusted based on reflected light from the optical disk. .

  When irradiating an optical disc with a light beam to record information on the optical disc or to reproduce information from the optical disc, it is necessary to control the light spot formed on the optical disc to follow the track of the optical disc. For this control, the amount of reflected light from the optical disc is detected, and the amount of deviation of the light spot from the track is detected as a tracking error signal. As a method for detecting this tracking error signal, for example, there is a differential push-pull method (DPP method). In this method, a grating (diffraction grating) is installed between the laser light source and the objective lens in the optical pickup, the laser beam is divided into three by the diffraction by the grating, and a light spot is formed on the optical disk. In this method, a tracking error signal is generated by a signal corresponding to the amount of reflected light from a spot.

  In this method, by rotating the grating around the axis of the laser beam, as shown in FIG. 1, the two sub-spots SP2 and SP3 are shifted from each other in the opposite direction by ½ of the track pitch with respect to the main spot SP1. It is necessary to adjust the angle so that it is located at the position. In FIG. 1, the track portions of the optical disk are patterned, and the land portions between the tracks are left white. This adjustment usually forms a light spot on a rotating disk, detects a signal corresponding to the amount of reflected light for each light spot with tracking control canceled, and removes a high-frequency component from the signal. The phase difference is adjusted to an appropriate value by adjusting the angle around the laser optical axis of the grating while measuring the phase with a phase meter or the like. Specifically, in FIG. 1, the phases of signals corresponding to the main spot SP1 and the sub spot SP2 or the main spot SP1 and the sub spot SP3 are shifted by 180 degrees as shown in FIGS. To be adjusted.

In this case, the maximum value of the intensity of the signal corresponding to the amount of reflected light is considered to be constant within a certain limited range as shown in Patent Document 1 below. It was found that the intensity level on the reference side of the signal pulsated as shown in FIGS. 3 (A) and 3 (B). This will be described with reference to the following Patent Document 2. In many optical pickups, in order to make the amount of emitted laser light constant, a part of the laser light directed to the optical disk is extracted by a beam splitter, and the intensity of the light is determined. The output of the laser beam is controlled so that the numerical value is detected by the light detection unit.
JP 7-70074 JP-A-8-287505

  However, since the light entering the light detection unit may include a small amount of reflected light reflected from the optical disk, if the amount of light reflected by the optical disk is large, the amount of laser light entering the light detection unit is small. Therefore, the amount of emitted laser light is controlled so as to decrease. On the contrary, if the amount of light reflected on the optical disk is small, the amount of laser light entering the light detection section is slightly reduced, so that the amount of emitted laser light is controlled to increase. Therefore, the signal corresponding to the main spot SP1 by the DPP method is as shown in FIG. 3A, and the signals corresponding to the sub-spots SP2 and SP3 are the signals on the reference side of each signal as shown in FIG. A pulsation appears in the intensity level. At the time of adjustment, these signals are generally passed through a low-pass filter to remove high-frequency components of the signal, but the signals corresponding to the main spot SP1 and the sub-spots SP2 and SP3 are caused by the pulsation. As shown by the broken lines in FIGS. 3A and 3B, the phase is slightly shifted from the envelope of the original signal.

  However, there is a difference in the amount of phase shift indicated by the broken lines in FIGS. 3A and 3B due to the difference in the way each pulsation occurs. For this reason, in the conventional apparatus, even if the grating is adjusted so that the phase difference between the two signals is shifted by 180 degrees, the three light spots are actually adjusted to positions slightly shifted from the normal positions. There is a problem that each light spot cannot be adjusted to an appropriate position.

  The present invention has been made to cope with the above-described problem, and an object of the present invention is to adjust the positions of the three light spots to normal positions even in an optical pickup in which pulsation exists in the intensity level on the reference side of the signal. It is an object of the present invention to provide an inspection apparatus and inspection method for an optical pickup that enable the above-mentioned.

  In order to achieve the above object, a feature of the present invention is that light having three light receiving elements for receiving reflected light from an optical disk by three light beams composed of a main beam, a preceding sub beam, and a following sub beam formed by a grating. An inspection apparatus for a pickup, wherein first and second received light signals respectively representing reflected light received by any two of the three light receiving elements are input and low pass filtering is performed respectively. In an optical pickup inspection apparatus comprising a second low-pass filter means and a phase difference detection means for detecting a phase difference between signals from the first and second low-pass filter means, the input to the first and second low-pass filter means And a pulsation removing means for removing pulsation of the intensity level on the reference side in the received light signal.

  In the inspection apparatus for an optical pickup according to the present invention configured as described above, even if pulsation occurs in the intensity level on the reference side of the received light signal corresponding to the amount of light reflected from the optical disk, the first and second low-pass Since the pulsation removing means removes the pulsation before performing the low-pass filter processing by the filter means, even if the low-pass filter processing is performed thereafter, no phase shift occurs in those output signals. Therefore, by adjusting the grating based on the output signal, the main beam, the preceding sub beam, and the succeeding sub beam can be adjusted to appropriate positions on the optical disc.

  The characteristics of the optical pickup inspection device can also be applied to the optical pickup inspection method.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a schematic block diagram showing an entire optical pickup inspection apparatus according to the embodiment.

This inspection apparatus includes a spindle motor 21 having a built-in encoder 21a. The spindle motor 21 is driven and controlled by the spindle motor control circuit 22 to rotationally drive the support table 23 on which the optical disk DK is assembled. The encoder 21 a detects the rotation of the spindle motor 21, that is, the rotation of the support table 23 (optical disk DK), and supplies a rotation detection signal representing the rotation of the spindle motor 21 to the spindle motor control circuit 22. The rotation detection signal is at a high level by a predetermined minute rotation angle that is out of phase with each other by an index signal INDEX that is generated every time the rotation position of the support table 23 (optical disk DK) comes to the reference rotation position. And pulse train signals φ _A and φ _B that repeat the low level and the low level.

  The spindle motor 21 is driven in the radial direction of the optical disk DK by a feed mechanism including a feed motor 24, a screw rod 25, and a support member 26 together with the encoder 21a and the support table 23. The feed motor 24 is rotationally controlled by a feed motor control circuit 27 to rotate the screw rod 25. The screw rod 25 is screwed to a nut (not shown) fixed to the support member 26. The screw rod 25, the support member 26, and the nut constitute a screw mechanism. Due to the rotation of the feed motor 24, the support member 26 is displaced together with the spindle motor 21 and the like in the axial direction of the screw rod 25, that is, in the radial direction of the optical disc DK.

The feed motor 24 also includes an encoder 24a similar to the encoder 21a described above. The encoder 24 a also supplies a rotation detection signal representing the rotation of the feed motor 24 to the feed motor control circuit 27 for controlling the rotation of the motor 24. This rotation detection signal is also composed of an index signal INDEX and pulse train signals φ _A and φ _B , similarly to the rotation detection signal of the encoder 21a.

  Here, the optical pickup 30 to be inspected to be assembled in the inspection apparatus will be described. The optical pickup 30 records data on a recordable optical disc DK such as a CD and a DVD, and reproduces data recorded on the optical disc DK. The optical pickup 30 includes a laser light source 31, a collimating lens 32, a grating (diffraction grating) 33, a polarizing beam splitter 34, a ¼ wavelength plate 35, an objective lens 36, a condensing lens 37, a cylindrical lens 38, and a photodetector 39. Yes. In this optical pickup 30, the optical disk DK is irradiated with the laser light from the laser light source 31 via the collimating lens 32, the grating 33, the polarizing beam splitter 34, the quarter wavelength plate 35, and the objective lens 36. The reflected light from the optical disk DK is received by the photodetector 39 via the objective lens 36, the quarter wavelength plate 35, the polarizing beam splitter 34, the condenser lens 37, and the cylindrical lens 38, and the signal recording state of the optical disk DK is represented. A light reception signal is output.

  In this case, the grating 33 receives one light beam emitted from the laser light source 31 and converted into parallel light by the collimator lens 32, and emits three light beams by diffraction. These three light beams are arranged in a line in the track direction of the optical disc DK, and are hereinafter referred to as a preceding sub beam, a main beam, and a subsequent sub beam in order along the rotation direction of the optical disc DK. The photo detector 39 includes a main beam light receiving element 39a, a preceding sub beam light receiving element 39b, and a subsequent sub beam light receiving element 39c. Each of the reflected lights is received and a voltage signal having a magnitude proportional to the amount of received light is output. The main beam light receiving element 39a is divided into four by two dividing lines along the track direction and the radial direction, and each of the four light receiving elements is divided into voltage signals A, B, C, D is output respectively. The preceding sub-beam light receiving element 39b and the succeeding sub-beam light receiving element 39c are divided into two by one dividing line along the track direction, and each of the two divided light receiving elements is a voltage signal E1 proportional to each received light amount. , E2 and F1, F2 are output.

  A laser drive circuit 41 for controlling the operation and stop of the laser light source 31 is connected to the laser light source 31. Each of the light receiving element outputs A, B, C, and D divided by the main beam light receiving element 39a is supplied to the focus error signal generation circuit. The focus error signal generation circuit 42 generates a focus error signal by the astigmatism method or the like and supplies the error signal to the focus servo circuit 43. The focus servo circuit 43 supplies the focus error signal to the drive circuit 44, and performs focus servo control of the focus actuator 36a for driving the objective lens 36 in the optical axis direction. Thus, the focal point of the laser beam is controlled so as to follow the recording layer of the optical disc DK.

  The main beam light receiving element 39 a and the subsequent sub-beam light receiving element 39 c are connected to the reproduction signal observation device 50. As shown in FIG. 5, the reproduction signal observation device 50 includes a reproduction signal generation circuit 51 connected to the main beam light receiving element 39a. The reproduction signal generation circuit 51 amplifies and outputs the light reception signal from the main beam light receiving element 39a as a reproduction signal. However, the reproduction signal generation circuit 51 adds all the output signals A, B, C, and D of the four light receiving elements of the main beam light receiving element 39a, and uses the addition result as a reproduction signal (so-called sum signal). SUM). In addition, the reproduction signal observation device 50 includes a reproduction signal generation circuit 62 connected to the subsequent sub-beam light receiving element 39c. The reproduction signal generation circuit 62 amplifies, adds, and outputs the light receiving element outputs F1 and F2 divided into two parts of the light receiving element 39c for the subsequent sub beam.

  The reproduction signal observation device 50 also includes noise removal circuits 52 and 63, low-pass filters 53 and 64, and a phase meter 70. As shown in FIG. 6, the noise removal circuits 52 and 63 include a capacitor C1, an operational amplifier OP1, resistors R1, R2, and R3, and a diode D1. Here, the capacitor C1 and the resistor R3 constitute a high-pass filter, the operational amplifier OP1 and the resistors R1 and R2 constitute an amplifier, and the high-pass filter, the amplifier, and the diode D1 constitute a clipper circuit. In this case, the diode D1 prohibits the anode potential from exceeding a predetermined potential (0.6 V). The low-pass filters 53 and 64 are connected to the noise removal circuits 52 and 63, respectively, remove high frequency components of the output signals from both the circuits 52 and 63 (low-pass filter processing), and output to the phase meter 70. . The cut-off frequency of the low-pass filters 53 and 64 is set to, for example, about 8.2 KHz. The phase meter 70 calculates and displays the phase between the two signals low-pass filtered by the low-pass filters 53 and 64. The phase meter 70 is also connected to the computer device 80, and receives an instruction signal from the computer device 80 and outputs a calculation result to the computer device 80.

  The computer device 80 includes a CPU, a ROM, a RAM, etc., or a gate array such as an FPGA and a PLD. By executing a program (not shown), three light beams emitted from the optical pickup 30 to the optical disc DK are recorded on the optical disc DK. A determination operation for irradiating a predetermined position is controlled. The computer device 80 is also connected to the spindle motor control circuit 22, the feed motor control circuit 27, and the laser drive circuit 41 described above for their control. The computer device 80 is connected to an input device 81 that is operated by a user to input information, and is also connected to a display device 82 that displays the calculation results, determination results, and the like.

  The operation of the embodiment configured as described above will be described. First, the operation of various circuits of the inspection apparatus including the computer device 80 is started by turning on a power switch (not shown). Then, the optical pickup 30 to be adjusted and inspected is assembled to the inspection apparatus. In this optical pickup 30, the rotation angle of the grating 33 is already adjusted so that the three light beams are positioned on the center line of the same track of the optical disc DK by other adjustments that are not described. An optical disk DK on which data is recorded in advance, such as a CD and a DVD used for inspection, is also set on the support table 23. Next, the input device 81 is operated to instruct the inspection device to adjust the optical pickup 30 and start the inspection. In response to this instruction, the computer device 80 outputs information representing the radial position of the optical disk DK irradiated with the light beam to the feed motor control circuit 27 for this adjustment and inspection. The feed motor control circuit 27 controls the rotation of the feed motor 24 using the rotation detection signal input from the encoder 24a, and causes the optical disk DK to have a diameter so that the light beam is irradiated to the input radial position. Move in the direction.

  Next, the computer device 80 sends information indicating the rotational speed of the optical disk DK for relatively moving the light spot at a predetermined reference linear speed at the radial position of the optical disk DK to the spindle motor control circuit 22. Output. The spindle motor control circuit 22 controls the rotation of the spindle motor 21 using the rotation detection signal input from the encoder 21a, and rotates the optical disc DK at the rotation speed.

  Next, the computer device 80 outputs an operation start signal of the laser light source 31 to the laser driving circuit 41. In response to this, the laser drive circuit 41 operates the laser light source 31, and the laser light source 31 starts to emit laser light. As the laser beam starts to be emitted, the optical disk DK is irradiated with three light beams including a preceding sub beam, a main beam, and a succeeding sub beam, thereby forming three light spots. In this case, the three light spots are arranged so as to be substantially on the center line of the same track. Reflected light from these three light spots is received by the main beam light-receiving element 39a, the preceding sub-beam light-receiving element 39b, and the subsequent sub-beam light-receiving element 39c.

  The main beam light receiving element 39a is divided into four parts, and the focus error signal generating circuit 42 generates a focus error signal based on the light receiving signals from the four light receiving elements divided into four parts, and the focus servo circuit 43, drive circuit 44, and Focus servo control of the objective lens 36 is performed in cooperation with the focus actuator 36a. In this case, the objective lens 36 is not subjected to tracking servo control.

  In order to omit the tracking servo control, the three light spots SP1 to SP3 move on the optical disk DK while crossing the track. In this adjustment, the phenomenon that the light spots SP1 to SP3 move on the optical disk DK while crossing the track is positively used. That is, since the light spots SP1 to SP3 cross the track, the amplitudes of the light reception signals by the main beam light receiving element 39a and the subsequent beam light receiving element 39c change. In this case, if the main spot SP1 and the succeeding sub-spot SP3 are shifted by a half of the track pitch in the radial direction, the change in the amplitude of both received light signals is a phase as shown in FIGS. Should be shifted by 180 degrees. In other words, if the phase shift of the amplitude change of both received light signals is 180 degrees, the main spot SP1 and the subsequent sub spot SP3 are shifted by ½ of the track pitch in the radial direction.

  On the other hand, light reception signals from the main beam light receiving element 39 a and the subsequent sub-beam light receiving element 39 c are supplied to the reproduction signal observation device 50. The reproduction signal observation device 50 also starts to operate upon receiving a start instruction signal from the computer device 80. The reproduction signal observation device 50 inputs each received light signal to the reproduction signal generation circuits 51 and 62 to generate a reproduction signal, and inputs it to the noise removal circuits 52 and 63. The noise removal circuits 52 and 63 remove the pulsation of the intensity level on the reference side of the reproduction signal and make it constant. Specifically, as shown in FIG. 7A, a DC component is removed by a high-pass filter composed of a capacitor C1 and a resistor R3, and the signal ground level (potential 0 level) is shifted to an appropriate position. Thus, the signal is amplified by an amplifier composed of an operational amplifier OP1 and resistors R1 and R2. Among the amplified signals, a signal having a voltage higher than a predetermined voltage in the forward direction (about 0.6 V), that is, a signal higher than the predetermined voltage (a broken line in FIG. 7A) from the ground level is cut by the diode D1 and pulsated. A certain signal with no signal is output (see FIG. 7B).

  Next, the signal is input to the low-pass filters 53 and 64, and a component having a high frequency is removed and only a component having a low frequency is obtained, that is, a signal representing an envelope of the input signal. In this case, the signals input to the low-pass filters 53 and 64 become constant signals having no pulsation in the intensity level on the reference side of the signal by the noise removal circuits 52 and 63, and therefore the output thereof is shown in FIG. There is no phase shift as indicated by the broken line in B). The signal is input to the phase meter 70, which measures the phase of the two signals and displays the result.

  In accordance with the display on the display device 82, the operator moves the three light spots SP1 to SP3 from the state where the three light spots SP1 to SP3 are formed on the center line of the same track of the optical disc DK to the position shown in FIG. Thus, the grating 33 is rotated in a predetermined direction by a predetermined angle. That is, the preceding sub-spot SP2 is shifted to the right side of the figure by 1/2 of the track pitch with respect to the main spot SP1, and the main spot SP1 is shifted to the right side of the figure by 1/2 of the track pitch with respect to the subsequent sub-spot SP3. To.

  Specifically, such adjustment is described. The computer device 80 issues a phase measurement instruction to the phase meter 70 and causes the phase meter 70 to display the phase difference between the two input signals. In this case, the phase meter 70 is supplied with a signal that is reproduced by the reproduction signal generation circuits 51 and 62, pulsation of the signal is removed by the noise removal circuits 52 and 63, and low-pass filtered by the low-pass filters 53 and 64. ing. That is, the phase meter 70 is supplied with two signals representing the amplitude change in FIGS. 2A and 2B, and the phase meter 70 displays the phase difference between these two signals.

  Instead of displaying the phase difference between the two signals by the phase meter 70, the computer device 80 may input the phase difference between the two signals from the phase meter 70 and display it on the display device 82. . Alternatively, the two signals themselves may be input to the computer device 80, and the phase difference between the two signals may be calculated and displayed. Further, instead of the phase difference, it is determined whether the phase difference between the two signals is within an allowable range, that is, whether the main spot SP1 and the subsequent sub-spot SP3 are shifted in the radial direction by ½ of the track pitch. Then, the determination result may be displayed on the display device 82.

  If the phase difference between the two signals is within the allowable range, it can be determined that the three light spots SP1 to SP3 are in the normal arrangement state of FIG. 1, and the operator ends the adjustment operation. On the other hand, if the phase difference between the two signals is not within the allowable range, it can be determined that the three light spots SP1 to SP3 are not in the normal arrangement state of FIG. 1, and the operator again adjusts the rotation of the grating 33 around the optical axis. Then, the adjustment operation is continued, and finally the adjustment is performed so that the three light spots SP1 to SP3 are in the normal arrangement state of FIG.

  As can be understood from the description of the operation, according to the embodiment, in the optical pickup 30 that forms the three light spots SP1 to SP3 on the optical disk DK, a signal corresponding to the reflected light amount of each of the light spots SP1 to SP3 is displayed. Even when pulsation occurs in the intensity level on the reference side, the intensity level on the reference side of the signal is made constant by the noise removal circuits 52 and 63 before the low-pass filter processing is performed by the low-pass filters 53 and 64. There is no phase shift between the two signals measured at 70. Accordingly, the phase of the signals corresponding to the main spot SP1 and the preceding subspot SP2 or the main spot SP1 and the succeeding subspot SP3 can be accurately adjusted to a phase relationship shifted by 180 degrees, and the preceding and succeeding subspots SP2, SP2 It is possible to adjust so that SP3 is formed at a normal position shifted to the opposite side by 1/2 of the track pitch with respect to the main spot SP1.

  Furthermore, the implementation of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

  In the embodiment, the position adjustment of the three light spots SP1 to SP3 is inspected by using both light reception signals from the main beam light receiving element 39a and the succeeding sub beam light receiving element 39c. However, instead of this, the position adjustment of the three light spots SP1 to SP3 may be inspected by using both light reception signals from the preceding sub-beam light receiving element 39b and the main beam light receiving element 39a. In this case, the light reception signal from the preceding sub-beam light receiving element 39b may be guided to the reproduction signal generation circuit 51, and the light reception signal from the main beam light reception element 39a may be guided to the reproduction signal generation circuit 62. Then, the reproduction signal generation circuit 51 amplifies and adds the light reception signals E1 and E2 from the preceding sub-beam light receiving element 39b and outputs them, and the reproduction signal generation circuit 62 receives the light reception signal A from the main beam light receiving element 39a. , B, C, D may be amplified and added to output.

  In the above embodiment, the present invention is applied to the adjustment of an optical pickup that adopts the DPP method as a tracking error detection method. However, the present invention is not limited to this, for example, The present invention can also be applied to the adjustment of a three-beam optical pickup. In this case, in the three-beam method, three light spots are formed at positions where the preceding and succeeding sub-spots SP2 and SP3 are shifted to the opposite sides by ¼ of the track pitch with respect to the main spot SP1 as shown in FIG. To be arranged. Therefore, if the rotational position of the grating 33 is adjusted so that the phases of the signals corresponding to the preceding sub spot SP2 and the subsequent sub spot SP3 are shifted from each other by 180 degrees as shown in FIGS. It becomes possible to adjust the three light spots to regular positions. Further, the rotational position of the grating 33 is adjusted so that the phases of the signals corresponding to the preceding sub spot SP2 or the succeeding sub spot SP3 and the main spot SP2 are shifted from each other by 90 degrees, so that the three light spots are normalized. It is also possible to adjust the position.

  In the above embodiment, in order to change the radial relative position between the optical pickup 30 and the optical disk DK, the spindle motor 21 and the support using the feed mechanism including the feed motor 24, the screw rod 25, the support member 26, and the like. The table 23 is moved. However, instead of this, the relative position in the radial direction between the optical pickup 30 and the optical disk DK may be changed by moving the entire optical pickup 30 in the radial direction of the optical disk DK by a feed mechanism.

It is explanatory drawing for demonstrating the position of three light spots by a DPP system. (A), (B) is a wave form diagram which shows roughly the signal utilized at the time of adjustment of a light spot. (A), (B) is a wave form diagram which shows exactly the signal used at the time of adjustment of a light spot. 1 is a block diagram schematically illustrating an entire optical pickup inspection apparatus according to an embodiment of the present invention. FIG. 5 is a detailed block diagram of the reproduction signal observation apparatus in FIG. 4. It is a detailed circuit diagram which shows an example of a noise removal circuit. (A) and (B) are signal waveform diagrams used when adjusting the light spot. It is explanatory drawing for demonstrating the position of three light spots by a 3 beam system.

Explanation of symbols

DK ... Optical disk, 21 ... Spindle motor, 24 ... Feed motor, 30 ... Optical pickup, 31 ... Laser light source, 33 ... Grating, 39 ... Photo detector, 50 ... Reproduction signal observation device, 52, 63 ... Noise removal circuit, 74 ... Phase Total, 80 ... computer equipment.

Claims (2)

An inspection apparatus for an optical pickup having three light receiving elements for receiving reflected light from an optical disk by three light beams composed of a main beam, a preceding sub beam and a following sub beam formed by a grating,
First and second low-pass filter means for inputting first and second light-receiving signals respectively representing reflected light received by any two of the three light-receiving elements and performing low-pass filter processing;
In an inspection apparatus for an optical pickup comprising phase difference detection means for detecting a phase difference between signals from the first and second low-pass filter means,
An inspection apparatus for an optical pickup, comprising: a pulsation removing unit that removes a pulsation of a reference-side intensity level in a received light signal input to the first and second low-pass filter units. An inspection method for an optical pickup having three light receiving elements for receiving reflected light from an optical disk by three light beams composed of a main beam, a preceding sub beam and a following sub beam formed by a grating,
The first and second received light signals respectively representing the reflected light received by any two of the three light receiving elements are input and low pass filtered, and the first low pass filtered first And an optical pickup inspection method for detecting a phase difference between the second light reception signals,
An inspection method for an optical pickup, characterized in that a reference-side intensity level pulsation in the first and second received light signals subjected to the low-pass filter processing is removed.

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