JP4958186B2 - Optical pickup inspection device, inspection method, inspection program, computer-readable recording medium, and optical pickup automatic adjustment device - Google Patents

Description

  The present invention relates to an optical pickup inspection apparatus and inspection method for recording / reproducing information using laser light, and an optical pickup automatic adjustment apparatus. Furthermore, the present invention relates to a program for causing the inspection apparatus to execute, and a computer-readable recording medium on which the program is recorded.

  In recent years, optical recording media such as compact discs (CDs) and digital versatile discs (DVDs) have been used in many fields such as computers, audios, and video.

  In order to record and reproduce information on the optical recording medium, it is necessary to irradiate the optical spot on the information recording surface of the optical recording medium so that the optical spot follows the track formed on the optical recording medium. is there. Control that causes the light spot to follow the track in this way is called tracking control.

  There are several known tracking control methods such as a phase difference method, a three-beam method, a push-pull method, and a differential push-pull (DPP) method. Hereinafter, the differential push-pull method will be described.

  In the differential push-pull method, a diffraction grating is installed in the optical path from the laser light source to the optical disc, the transmitted light (0th order light) of the diffraction grating is used as the main beam, ± 1st order diffracted light is used as the sub beam, and tracking control using 3 beams. It is a method. The three beams are applied to the optical disc so that the spot interval on the optical disc is an odd multiple of 1/2 the track pitch. Then, the push-pull signal of the reflected light of each of the main beam and the sub beam is detected, and the differential signal of the detected signal is used as the tracking error signal. In the differential push-pull method, when the irradiation position of the light beam is shifted in the radial direction of the optical disc, offsets generated in the push-pull signals of the main beam and the sub beam cancel each other. As a result, since the offset of the tracking error signal can be reduced, stable tracking control can be performed.

  However, when the spot interval of the three beams deviates from an odd multiple of ½ of the track pitch, the offset cannot be canceled. As a result, the amplitude of the tracking error signal decreases, and tracking control may become unstable.

  As an adjustment method of an optical pickup used in the differential push-pull method, for example, a technique disclosed in Japanese Patent Laid-Open No. 2005-44424 (Patent Document 1) is known. In this technique, the amplitude change of the differential push-pull signal is observed when the beam interval between the main beam and the sub beam is large and the eccentricity of the optical recording medium is large. Then, when the envelope of the differential push-pull signal obtained per rotation of the optical disk is detected, the optical pickup is adjusted so that the amplitude has periodicity and the maximum value and the minimum value are obtained at least twice each. Is done.

  Although the technical field is different from the above-described known technique, signal processing techniques that focus on signal waveform envelopes and extreme values are disclosed in Japanese Patent Application Laid-Open No. 2007-209882 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2004-79079. (Patent Document 3). Japanese Patent Laying-Open No. 2007-209782 (Patent Document 2) discloses a technique related to signal processing of an output signal of a pulse oximeter for determining blood oxygen saturation and cardiac output. Japanese Patent Laying-Open No. 2004-79079 (Patent Document 3) discloses a technique for generating an off-track signal indicating that an irradiation position of a laser beam is located other than a track based on a tracking error signal.

JP 2005-44424 A JP 2007-209782 A JP 2004-79079 A

  Thus, in order to stabilize the tracking control using the differential push-pull method, the positional relationship of the diffraction grating with respect to the light source is set so that the spot interval of the three beams is an integral multiple of 1/2 of the track pitch. It is necessary to adjust accurately.

  However, when the technique disclosed in the above Japanese Patent Application Laid-Open No. 2005-44424 (Patent Document 1) is used, it is difficult to accurately determine the quality of the diffraction grating arrangement. In the case of Japanese Patent Application Laid-Open No. 2005-44424 (Patent Document 1), when an envelope of a differential push-pull signal obtained per rotation of an optical disc is detected, the amplitude has periodicity, and a maximum value and a minimum value are The optical pickup is adjusted so that it can be obtained at least twice. In this case, it is not clear how much periodicity is recognized in the amplitude of the envelope so that the optical pickup can be judged as good. In addition, since the quality determination is performed based on the waveform of the envelope of the differential push-pull signal obtained per rotation of the optical disk, there is also a problem that the determination can be made with accuracy only when the eccentricity of the optical disk is large.

  Accordingly, an object of the present invention is to provide an inspection apparatus and an inspection method capable of inspecting a tracking control type optical pickup by the differential push-pull method with high accuracy. Furthermore, an object of the present invention is to provide a program for causing the inspection apparatus to execute and a computer-readable recording medium on which the program is recorded. Furthermore, an object of the present invention is to provide an automatic adjustment device that automatically adjusts a tracking control type optical pickup based on a differential push-pull method with high accuracy.

  In summary, the present invention is an optical pickup inspection apparatus, which includes an error signal generation unit, an AD conversion unit, a storage unit, a waveform extraction unit, an extreme value calculation unit, and a determination unit. Here, the optical pickup includes a laser light source, an optical branching element, an objective lens, an actuator, and a plurality of photodetectors. The light branching element branches light emitted from the laser light source into a plurality of light beams including a main beam and at least two sub beams. The objective lens focuses each of the plurality of light beams on the optical recording medium. The actuator repeatedly displaces the objective lens in the direction crossing the track of the optical recording medium. The plurality of photodetectors respectively detect a plurality of reflected lights generated by reflecting each of the plurality of light beams on the optical recording medium. The error signal generation unit generates a differential push-pull signal based on the outputs of the plurality of photodetectors as a tracking error signal. The AD conversion unit digitally converts the differential push-pull signal obtained while the objective lens is repeatedly displaced. The storage unit stores first time-series data obtained by digitally converting the differential push-pull signal. The waveform extraction unit extracts the first waveform based on the first time-series data stored in the storage unit. The first waveform at this time is a waveform based on one of the upper and lower envelopes of the first time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes. The extreme value calculation unit calculates a plurality of maximum values or minimum values of the first waveform. The determination unit determines whether the arrangement of the optical branching element with respect to the laser light source is good or not based on whether or not the variation of the plurality of maximum values or minimum values of the first waveform calculated by the extreme value calculation unit is within a predetermined range. To do.

  According to the inspection apparatus for an optical pickup described above, the inspection of the optical pickup can be performed with high accuracy by evaluating the variation in the extreme value of the first waveform extracted from the time series data. As a result, variations in adjustment of the optical pickup can be suppressed, adjustment time can be shortened, and labor costs can be reduced.

  Preferably, the waveform extraction unit includes an end point setting unit and an envelope generation unit. The end point setting unit sets at least one of the left and right end points for each of the upper and lower envelopes of the first time-series data. The envelope generation unit sequentially extracts data points that satisfy a predetermined condition from the first time-series data in the positive or negative direction of the time axis starting from one of the left and right end points, thereby generating upper and lower envelopes. Generate each. Here, the predetermined condition is that the slope of a straight line passing through adjacent data points is within a predetermined range.

  According to the above configuration, since the change in the amplitude of the envelope is limited so as to satisfy the predetermined condition, even if the first time-series data includes a noise component, the influence of noise is suppressed. An envelope can be generated.

  Preferably, the envelope generator generates a plurality of first data points extracted from the first time-series data in the positive direction of the time axis and a plurality of second data points extracted in the negative direction of the time axis. Each of the upper and lower envelopes is generated by averaging. Therefore, an envelope can be generated with higher accuracy.

  Preferably, the envelope generator generates the first time-series data by using, as noise, a data point that exceeds a predetermined threshold and deviates from the upper and lower envelopes among the data points of the first time-series data. Then, each of the upper and lower envelopes is generated again using the first time-series data from which noise is removed. Therefore, even when the first time-series data includes a noise component, it is possible to remove the influence of noise and calculate the envelope with high accuracy.

  Preferably, when setting each of the left and right end points, the end point setting unit sets a predetermined number of data points when arranging a predetermined number of data points in order of size from the beginning or end of the first time series data. Set the point value to the end point value.

  According to the above configuration, since the first or last data point or 0 point of the first time series data is not an end point, the influence of noise can be suppressed and the calculation accuracy at the end of the envelope can be increased. . As a result, the accuracy of the pass / fail determination by the determination unit can be improved.

  Preferably, the extreme value calculation unit includes a sampling waveform generation unit, a smoothing unit, and a minimum point extraction unit as a configuration for calculating a plurality of minimum values of the first waveform. The sampling waveform generation unit divides the first waveform into a plurality of sections, and generates a sampling waveform composed of the minimum points of the plurality of sections. The smoothing unit generates a smoothed waveform obtained by moving and averaging the sampling waveform. The local minimum point extraction unit extracts a plurality of negative intervals in which a value obtained by subtracting the smoothed waveform from the sampling waveform is negative, and extracts a minimum point of the sampling waveform in each of the plurality of negative intervals as a local minimum point of the first waveform. To do.

  Preferably, the extreme value calculation unit includes a sampling waveform generation unit, a smoothing unit, and a maximum point extraction unit as a configuration for calculating a plurality of maximum values of the first waveform. The sampling waveform generation unit divides the first waveform into a plurality of sections, and generates a sampling waveform composed of the maximum points of the plurality of sections. The smoothing unit generates a smoothed waveform obtained by moving and averaging the sampling waveform. The maximum point extraction unit extracts a plurality of positive intervals in which the value obtained by subtracting the smoothed waveform from the sampling waveform is positive, and extracts the maximum point of the sampling waveform in each of the plurality of positive intervals as the maximum point of the first waveform. To do.

  According to the configuration of the extreme value calculation unit described above, the maximum point or the minimum point is extracted using the sampling waveform in which the number of data of the first waveform is reduced, so that the noise component included in the original first waveform And the maximum point or the minimum point can be extracted with high accuracy. In addition, since the maximum point or the minimum point is extracted using the sampling waveform in which the number of data is reduced, the processing time of the computer can be shortened. Further, since the maximum point or the minimum point is extracted using the smoothed waveform obtained by smoothing the sampling waveform by the moving average, the position of the maximum point or the minimum point can be accurately detected even when the change in the amplitude of the first waveform is significant. Can be detected. As a result, it is possible to improve the accuracy of the quality determination by the determination unit.

  The extreme value calculation unit includes a sampling waveform generation unit, a smoothing unit, and a minimum point extraction unit as another preferable configuration when calculating a plurality of minimum values of the first waveform. The sampling waveform generation unit divides the first waveform into a plurality of sections, and generates a sampling waveform composed of the minimum points of the plurality of sections. The smoothing unit generates a smoothed waveform obtained by moving and averaging the sampling waveform. The local minimum point extraction unit extracts a plurality of negative sections in which a value obtained by subtracting the smoothed waveform from the sampling waveform is negative, and points on the first waveform corresponding to the centroid position of the sampling waveform in each of the plurality of negative sections Are extracted as the minimum points of the first waveform.

  In addition, the extreme value calculation unit includes a sampling waveform generation unit, a smoothing unit, and a maximum point extraction unit as another preferable configuration when calculating a plurality of maximum values of the first waveform. The sampling waveform generation unit divides the first waveform into a plurality of sections, and generates a sampling waveform composed of the maximum points of the plurality of sections. The smoothing unit generates a smoothed waveform obtained by moving and averaging the sampling waveform. The local maximum point extraction unit extracts a plurality of positive intervals in which a value obtained by subtracting the smoothed waveform from the sampling waveform is positive, and points on the first waveform corresponding to the centroid position of the sampling waveform in each of the plurality of positive intervals Are extracted as local maximum points of the first waveform.

  According to the configuration of the extreme value calculation unit described above, the maximum point or the minimum point of the first waveform is extracted using the gravity center position of the sampling waveform in each positive interval or negative interval. Even when the component is included, it is possible to accurately extract the position of the appropriate maximum or minimum point. As a result, it is possible to improve the accuracy of the quality determination in the determination unit.

  Preferably, the determination unit includes an extreme value classification unit and a comparison unit. The extreme value classification unit classifies the plurality of maximum values or minimum values calculated by the extreme value calculation unit into first and second groups. The comparison unit compares the average value of the plurality of local maximum values or local minimum values belonging to the first group with the average value of the plurality of local maximum values or local minimum values belonging to the second group, so that the optical branching element for the laser light source The quality of the arrangement is determined.

  Usually, when the objective lens is displaced to the inner peripheral side in the radial direction and the laser beam is irradiated to the inner peripheral side of the optical disc (optical recording medium), it is classified into the first group. The case where the laser beam is irradiated on the outer peripheral side of the optical disc by being displaced to is classified into the second group. At this time, the quality of the optical pickup can be determined with high accuracy by comparing the average value of the maximum value or the minimum value of the first group with the average value of the maximum value or the minimum value of the second group.

  Preferably, the extreme value classification unit classifies a plurality of local maximum values or local minimum values calculated by the extreme value calculation unit into first and second groups alternately in the time order of the first time-series data. As a result, a plurality of maximum values and minimum values can be easily classified into the first and second groups in association with the displacement of the objective lens.

  Preferably, the error signal generation unit further generates a main push-pull signal based on an output of a photodetector that detects reflected light of the main beam among the plurality of photodetectors. The AD converter further digitally converts the main push-pull signal obtained while the objective lens is repeatedly displaced. The storage unit further stores second time-series data obtained by digitally converting the main push-pull signal. The waveform extraction unit further extracts a second waveform based on the second time series data stored in the storage unit. The second waveform at this time is a waveform based on one of the upper and lower envelopes of the second time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes. The extreme value calculation unit further calculates a plurality of maximum values or minimum values of the second waveform. In this case, the extreme value classification unit includes the maximum value or the minimum value of the second waveform calculated by the extreme value calculation unit among the plurality of maximum values or minimum values of the first waveform calculated by the extreme value calculation unit. The maximum value or the minimum value obtained at substantially the same time as the time at which is given is classified into the first group, and the remaining maximum value or minimum value is classified into the second group.

  By using the push-pull signal of the main beam in this way, extreme values are classified with high accuracy when the laser beam is irradiated on the inner periphery side of the optical disc and when the laser beam is irradiated on the outer periphery side of the optical disc. be able to.

  Preferably, the error signal generation unit further generates a main push-pull signal based on an output of a photodetector that detects reflected light of the main beam among the plurality of photodetectors. The AD converter further digitally converts the main push-pull signal obtained while the objective lens is repeatedly displaced. The storage unit further stores second time-series data obtained by digitally converting the main push-pull signal. The waveform extraction unit further extracts a second waveform based on the second time series data stored in the storage unit. The second waveform at this time is a waveform based on one of the upper and lower envelopes of the second time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes. The extreme value calculation unit further calculates a plurality of maximum values and minimum values of the second waveform. In this case, the extreme value classification unit is obtained at substantially the same time as the time when the local waveform of the second waveform is given among the plurality of local maximum values or local minimum values calculated by the extreme value calculation unit. The maximum value or the minimum value is classified into the first group, and the maximum value or the minimum value obtained at substantially the same time as the time when the maximum value of the second waveform is given is classified into the second group.

  By using the push-pull signal of the main beam in this way, extreme values are classified with higher accuracy when the laser beam is applied to the inner periphery of the optical disc and when the laser beam is applied to the outer periphery of the optical disc. can do.

  In another aspect, the present invention is an optical pickup inspection method for inspecting an optical pickup including a laser light source, an optical branching element, an objective lens, an actuator, and a plurality of photodetectors. Here, the light branching element branches light emitted from the laser light source into a plurality of light beams including a main beam and at least two sub beams. The objective lens focuses each of the plurality of light beams on the optical recording medium. The actuator repeatedly displaces the objective lens in the direction crossing the track of the optical recording medium. The plurality of photodetectors respectively detect a plurality of reflected lights generated by reflecting each of the plurality of light beams on the optical recording medium. At this time, the optical pickup inspection method includes a step of generating a differential push-pull signal based on outputs of a plurality of photodetectors as a tracking error signal, and a differential obtained while the objective lens is repeatedly displaced. Based on the step of digitally converting the push-pull signal, the step of storing the first time-series data obtained by digitally converting the differential push-pull signal, and the first time-series data stored in the step of storing. Extracting the waveform. Here, the first waveform is a waveform based on one of the upper and lower envelopes of the first time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes. The optical pickup inspection method includes a step of calculating a plurality of maximum values or minimum values of a first waveform, and a variation of the plurality of maximum values or minimum values of the first waveform calculated in the calculating step within a predetermined range. And determining whether or not the arrangement of the optical branching element with respect to the laser light source is good.

  In yet another aspect, the present invention provides an inspection program for inspecting an optical pickup including a laser light source, an optical branching element, an objective lens, an actuator, and a plurality of photodetectors. Here, the light branching element branches light emitted from the laser light source into a plurality of light beams including a main beam and at least two sub beams. The objective lens focuses each of the plurality of light beams on the optical recording medium. The actuator repeatedly displaces the objective lens in the direction crossing the track of the optical recording medium. The plurality of photodetectors respectively detect a plurality of reflected lights generated by reflecting each of the plurality of light beams on the optical recording medium. At this time, the inspection program causes the differential push-pull signal generated based on the outputs of the plurality of photodetectors and digitally converted as the first time-series data to the computer while the objective lens is repeatedly displaced. A step of storing and a step of extracting the first waveform based on the first time-series data stored in the storing step are executed. Here, the first waveform is a waveform based on one of the upper and lower envelopes of the first time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes. The inspection program causes the computer to calculate a plurality of maximum values or minimum values of the first waveform, and a variation in the plurality of maximum values or minimum values of the first waveform calculated in the calculating step to be within a predetermined range. And determining whether the arrangement of the light branching element with respect to the laser light source is good or not is further executed.

  Moreover, this invention is a computer-readable recording medium which recorded said test | inspection program in another situation.

  According to another aspect of the present invention, there is provided an automatic adjustment device for an optical pickup, an error signal generation unit, an AD conversion unit, a storage unit, a waveform extraction unit, an extreme value calculation unit, and a determination unit. And an adjustment unit. Here, the optical pickup includes a laser light source, an optical branching element, an objective lens, an actuator, and a plurality of photodetectors. The light branching element branches light emitted from the laser light source into a plurality of light beams including a main beam and at least two sub beams. The objective lens focuses each of the plurality of light beams on the optical recording medium. The actuator repeatedly displaces the objective lens in the direction crossing the track of the optical recording medium. The plurality of photodetectors respectively detect a plurality of reflected lights generated by reflecting each of the plurality of light beams on the optical recording medium. The error signal generation unit generates a differential push-pull signal based on the outputs of the plurality of photodetectors as a tracking error signal. The AD conversion unit digitally converts the differential push-pull signal obtained while the objective lens is repeatedly displaced. The storage unit stores first time-series data obtained by digitally converting the differential push-pull signal. The waveform extraction unit extracts the first waveform based on the first time-series data stored in the storage unit. The first waveform at this time is a waveform based on one of the upper and lower envelopes of the first time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes. The extreme value calculation unit calculates a plurality of maximum values or minimum values of the first waveform. The determination unit determines whether the arrangement of the optical branching element with respect to the laser light source is good or not based on whether or not the variation of the plurality of maximum values or minimum values of the first waveform calculated by the extreme value calculation unit is within a predetermined range. To do. The adjustment unit adjusts the arrangement of the optical branching element with respect to the laser light source according to the determination result of the determination unit.

  As described above, according to the present invention, it is possible to improve the inspection accuracy of a tracking control type optical pickup using the differential push-pull method.

It is a figure which shows schematic structure of the test | inspection apparatus 11 of the optical pick-up 101 by Embodiment 1 of this invention. FIG. 4 is a diagram showing irradiation positions of three beams condensed on the optical recording medium 106. FIG. 3 is a diagram illustrating the configuration of a light detection unit 110 and an error signal generation unit 221. It is a schematic diagram which shows an example of the signal waveform of the differential push pull signal DPP. It is a block diagram which shows the hardware constitutions of the computer 201 of the test | inspection apparatus 11 of FIG. It is a block diagram which shows the structure of the software of the computer 201 which comprises the test | inspection apparatus 11 of FIG. It is a flowchart which shows the test | inspection procedure of the test | inspection apparatus 11 of an optical pick-up. It is a figure which shows an example of the time series data 320 output from AD conversion part 202. It is the flowchart which showed the procedure of step S504 of FIG. 7 in more detail. It is a figure for demonstrating the process sequence of step S603 of FIG. It is a figure for demonstrating the process sequence of step S604 of FIG. 10 is a flowchart showing the procedure of steps S603 and S604 of FIG. It is a figure for demonstrating the process sequence of step S605 of FIG. It is a figure for demonstrating the process sequence of step S607 of FIG. It is a figure which shows the upper and lower envelopes 321 and 322 produced | generated based on the time series data 320 shown in FIG. It is a figure which shows the low frequency waveform 323 produced | generated from the upper and lower envelopes 321 and 322 of FIG. It is the flowchart which showed the procedure of step S506 of FIG. 7 in more detail. It is a figure for demonstrating the process sequence of step S551 of FIG. It is a figure which shows the sampling waveform 324 produced | generated by step S551 of FIG. It is a figure for demonstrating the process sequence of step S553 of FIG. It is a figure which shows the position of minimum point V1-V5 determined on the low frequency waveform 323. FIG. It is the flowchart which showed the procedure of step S507 of FIG. 7 in more detail. It is a figure which shows an example of a differential push pull signal. It is a figure which shows an example of the signal containing a maximum point and a minimum point. It is a figure which shows the sampling waveform 326 produced | generated by step S551 of FIG. It is a figure for demonstrating the process sequence of step S553 of FIG. It is a figure which shows the time series data 328 of the main push pull signal MPP, and the upper and lower envelopes 329 and 330 produced | generated. It is a figure which shows the low frequency waveform 331 produced | generated from the upper and lower envelopes 329 and 330 of FIG. FIG. 10 is a diagram for explaining a method of classifying a plurality of minimum points of a low-frequency waveform 323 in the second embodiment. FIG. 10 is a diagram for describing a method for classifying a plurality of minimum points of a low-frequency waveform 323 according to Embodiment 3. It is a figure for demonstrating the process sequence of step S553 of FIG. It is a block diagram which shows schematic structure of the automatic adjustment apparatus 12 of the optical pick-up by Embodiment 5 of this invention. It is a block diagram which shows the software structure of the computer 201A which comprises the automatic adjustment apparatus 12 of FIG. It is a flowchart which shows the adjustment procedure by the automatic adjustment apparatus 12 of an optical pick-up.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

[Embodiment 1]
(Schematic configuration of optical pickup and its inspection device)
FIG. 1 is a diagram showing a schematic configuration of an inspection apparatus 11 for an optical pickup 101 according to Embodiment 1 of the present invention.

  Referring to FIG. 1, an optical pickup 101 is a device that reads information recorded on an optical recording medium 106 by irradiating an optical recording medium (optical disk) 106 rotated by a spindle motor 112 with laser light. .

  An optical pickup 101 in FIG. 1 includes a semiconductor laser 102 as a laser light source, a collimator lens 103, a diffraction grating 104 as an optical branching element, a beam splitter 105, and an objective for condensing laser light on an optical recording medium 106. Lens 107, actuator 111 that drives objective lens 107, reflected light condensing lens 108 that condenses the light reflected by optical recording medium 106, cylindrical lens 109, and a plurality of photodetectors 131, 132, and 133 And a light detection unit 110 having

  The collimator lens 103 converts the light beam emitted from the semiconductor laser 102 into parallel light.

  The diffraction grating 104 divides the parallel light output from the collimator lens 103 into three beams including one main beam (0th order light) and two sub beams (± 1st order diffracted light). Each beam passes through the beam splitter 105 and is collected on the optical recording medium 106 by the objective lens 107.

  The actuator 111 displaces the objective lens 107 with a drive coil. When reading information recorded on the optical recording medium 106, the actuator 111 is driven so as to keep the distance between the optical recording medium 106 and the objective lens 107 constant (focus servo control). Further, at the time of reading information, the actuator 111 is driven so that the irradiation position of the light beam follows the information track of the optical recording medium 106 (tracking servo control).

  FIG. 2 is a diagram showing irradiation positions of three beams condensed on the optical recording medium 106. Referring to FIG. 2, the irradiation position of main beam 121 is controlled by tracking servo control so that main beam 121 is irradiated to the center of information track 126. At this time, the sub beams 122 and 123 are irradiated with a shift of ½ track left and right with respect to the main beam 121, respectively. That is, the sub beam 122 is applied to the center of the track 126 and the track 125 adjacent to the left side thereof, and the sub beam 123 is applied to the center of the track 126 and the track 127 adjacent to the right side thereof.

  Referring again to FIG. 1, the three beams 121, 122, and 123 are reflected by the optical recording medium 106, respectively. The three reflected lights generated thereby are deflected by the beam splitter 105, pass through the reflected light collecting lens 108 and the cylindrical lens 109, and are guided to the light detection unit 110. A tracking error signal is generated from the reflected light guided to the light detection unit 110 by an error signal generation unit 221 described later with reference to FIG. The cylindrical lens 109 is provided to perform focus servo by the astigmatism method.

FIG. 3 is a diagram illustrating the configuration of the light detection unit 110 and the error signal generation unit 221.
Referring to FIG. 3, light detection unit 110 includes a main beam quadrant photodetector 131 and two sub-beams quadrant photodetectors 132 and 133. The light receiving surface of the four-divided photodetector 131 is divided into four light receiving elements (A, B, C, D). In addition, the light receiving surface of the two-divided photodetector 132 is divided into two light receiving elements (E, F), and the light receiving surface of the two-divided photodetector 133 is divided into two light receiving elements (G, H). Each of these light receiving elements (A to H) detects light independently and outputs a signal corresponding to the detected light intensity. In FIG. 3, the light beams applied to the photodetectors 131 to 133 are indicated by broken lines. Further, since the astigmatism method is used for focus control, the direction of the track on the optical disc and the direction of the track on the light receiving element are shifted by 90 degrees. Therefore, also in FIG. 3, the direction of the track on the light receiving element is shifted by 90 degrees.

  3 generates the push-pull signals MPP, SPP1, and SPP2 for each of the photodetectors 131 to 133, and the differential push-pull signal based on these push-pull signals MPP, SPP1, and SPP2. Generate DPP. The optical pickup inspection device 11 uses a differential push-pull signal DPP as a tracking error signal.

  The error signal generation unit 221 includes subtracters 141, 142, 143, 146, an adder 144, and a constant multiplier 145. In the case of the first embodiment, these computing units 141 to 146 are configured using an analog circuit such as an operational amplifier.

  The subtracter 141 outputs a difference signal between the light receiving elements A and D and the light receiving elements B and C as the main push-pull signal MPP. The subtractor 142 outputs a difference signal between the light receiving element E and the light receiving element F as a sub push-pull signal SPP1. The subtractor 143 outputs a difference signal between the light receiving element G and the light receiving element H as a sub push-pull signal SPP2. The adder 144 outputs a sum signal of the sub push-pull signals SPP1 and SPP2 as the sub push-pull signal SPP. The subtractor 146 outputs a difference signal between the main push-pull signal MPP and the sub push-pull signal SPP multiplied by a constant k by the constant multiplier 145 as a differential push-pull signal DPP. When the intensities of the optical signals received by the light receiving elements A to H are a to h, the above relationship is expressed as the following equation.

DPP = MPP-k × SPP (1)
MPP = (a + d)-(b + c) (2)
SPP = SPP1 + SPP2, SPP1 = ef, SPP2 = g−h (3)
Here, the coefficient k is for correcting the difference between the light intensity of the 0th order light and the light intensity of the + 1st order light and the −1st order light. For example, when the light intensity ratio is 0th order light: + 1st order light: −1st order light = I0: I1: I1, the coefficient k = I0 / (2 × I1).

  Referring to FIG. 1 again, the inspection apparatus 11 includes the error signal generation unit 221, the computer 201, and a display device 207 that displays the inspection result.

  The computer 201 uses the differential push-pull signal DPP output from the error signal generation unit 221 to determine whether the position and orientation of the diffraction grating 104 with respect to the semiconductor laser 102 are appropriate. Therefore, the computer 201 first controls the optical pickup 101 so that only the focus servo is performed without performing the tracking servo after the optical recording medium 106 is rotated by the spindle motor 112. Thereafter, the computer 201 causes the actuator 111 to repeatedly displace the objective lens 107 in the radial direction (the direction crossing the track) of the optical recording medium 106 on the inner peripheral side and the outer peripheral side. As a result, the irradiation position of the light beam on the optical recording medium 106 also reciprocates between the inner peripheral side and the outer peripheral side in the radial direction. The computer 201 analyzes the time series data of the differential push-pull signal DPP obtained at this time to determine whether or not the arrangement of the diffraction grating 104 with respect to the semiconductor laser 102 is appropriate. Hereinafter, an outline of signal processing by the computer 201 will be described with reference to specific waveforms.

  FIG. 4 is a schematic diagram illustrating an example of a signal waveform of the differential push-pull signal DPP. 4A and 4B are examples of waveforms when the arrangement of the diffraction grating 104 is appropriate, and FIG. 4C is an example of a waveform when the arrangement of the diffraction grating 104 is inappropriate. 4A to 4C, the X axis represents the time axis, and the Y axis represents the signal strength of the differential push-pull signal DPP.

  First, referring to FIG. 4A, when the spot interval of the three beams is an odd multiple of ½ of the track pitch, the differential push-pull signal DPP is represented by each push-pull signal MPP, The offsets generated in the SPP cancel each other. As a result, in the state where only the focus servo is performed without performing the tracking servo, when the objective lens 107 of FIG. 1 is alternately shifted to the outer peripheral side and the inner peripheral side in the radial direction of the optical recording medium 106, As shown in FIG. 4A, a waveform of a differential push-pull signal DPP that periodically changes with a substantially uniform amplitude is obtained. The periodic change of the differential push-pull signal DPP seen in FIG. 4A is due to the signal change when the optical spot crosses the track of the optical recording medium 106.

  However, even if the arrangement of the diffraction grating 104 is appropriate, a signal waveform having a uniform amplitude as shown in FIG. 4A is hardly obtained. For example, the track pitch of DVD-R is 0.74 μm, while the track pitch of DVD-RAM (Type II) is 0.615 μm. For this reason, in the case of DVD-R, even in the case of DVD-RAM (Type II), even if the optical pickup in which the offset generated in each push-pull signal MPP, SPP is canceled cleanly as shown in FIG. The above offset is not completely canceled.

  As a result, as shown in FIG. 4B, the waveform of the differential push-pull signal DPP includes the waveform of the lower frequency component in addition to the waveform of the frequency component resulting from the light spot crossing the track. It is. That is, as shown in FIG. 4B, a change occurs in the amplitude of the differential push-pull signal DPP, and a peak portion 81 having a large amplitude and a valley portion 82 having a large amplitude appear periodically.

  Such a change in amplitude corresponds to the displacement of the objective lens 107 in the radial direction of the optical recording medium 106. Usually, the peak portion 81 is a case where the center of the objective lens 107 is located in the center portion in the radial direction of the optical recording medium 106, and the valley portion 82 is a center portion of the objective lens 107 in the radial direction of the optical recording medium 106. It is a case where it is located in the inner peripheral side or outer peripheral side. The reason for this is as follows.

  The normal optical pickup is adjusted so that the light beam passes through the center of the objective lens 107 when the center of the objective lens 107 is located at the center of the optical recording medium 106 in the radial direction. Therefore, when the objective lens 107 is shifted to the inner or outer peripheral side of the optical recording medium 106, the center of the light beam is shifted from the center of the objective lens 107. Therefore, variations in the intensity of the three beams become more conspicuous on the inner circumference side and the outer circumference side of the optical recording medium 106, and as a result, the intensity of the differential push-pull signal DPP becomes weaker.

  When the arrangement of the diffraction grating 104 with respect to the laser light source is inappropriate with respect to these signal waveforms and the spot distances between the three beams are different, the differential push-pull as shown in FIG. Variations also occur in the amplitude of the signal DPP. That is, in the case of FIG. 4B, the amplitude of the valley portion 82 is almost constant, whereas in the case of FIG. 4C, the valley portions 82A and 82B having different amplitudes are alternately arranged. appear. 4C corresponds to the case where one of the valley portions 82A and 82B is located on the inner peripheral side of the optical recording medium 106, and the other valley portion corresponds to the objective lens 107. This corresponds to the case where the center is located on the outer peripheral side. Further, the peak 81, which is a portion having a larger amplitude than the valleys 82A and 82B, corresponds to the case where the center of the objective lens 107 is located at the center of the optical recording medium 106 in the radial direction.

  As described above, the waveform of the low-frequency component corresponding to the displacement of the objective lens 107 in the waveform of the differential push-pull signal DPP differs depending on the quality of the arrangement of the diffraction grating 104 in FIG. Therefore, the inspection apparatus 11 for the optical pickup in FIG. 1 determines the quality of the arrangement of the diffraction grating 104 using the difference in the waveform of the low frequency component. Hereinafter, the waveform of the frequency component that changes corresponding to the displacement of the objective lens 107 is referred to as a low-frequency waveform.

  Specifically, the computer 201 of the inspection apparatus 11 generates upper and lower envelopes of time series data of the differential push-pull signal DPP. And the computer 201 calculates | requires the waveform of the difference of this upper and lower envelope as said low frequency waveform, and calculates the several minimum value of the calculated | required waveform. Then, the computer 201 determines that the arrangement of the diffraction grating 104 is appropriate when the variation of the plurality of calculated minimum values is smaller than a predetermined threshold value. Details of the configuration and operation of the optical pickup inspection apparatus 11 will be described below.

(Hardware configuration of optical pickup inspection device)
FIG. 5 is a block diagram showing a hardware configuration of the computer 201 of the inspection apparatus 11 of FIG. Referring to FIG. 5, computer 201 includes an AD (Analog to Digital) conversion unit 202, a storage device 203, a calculation unit 204, an output unit 205, an input unit 206, and communication interfaces 208A and 208B. .

  The AD converter 202 converts the differential push-pull signal DPP, which is an analog signal generated by the error signal generator 221, into time-series digital data.

  The storage device 203 stores data given from outside the computer 201 and data generated by the computer 201. The data given from the outside is, for example, time-series digital data converted by the AD conversion unit 202, a set value that defines the operation of the computer 201, or the like. The data generated in the computer 201 is, for example, data for signal processing calculated by the arithmetic unit 204, a result of pass / fail judgment of the optical pickup 101, and the like.

  The storage device 203 includes an external storage device that stores a large amount of data such as a hard disk, a nonvolatile and volatile semiconductor memory, or the like.

  The arithmetic unit 204 is a microprocessor that executes processing of data stored in the storage device 203 in accordance with a program created in advance. The arithmetic unit 204 outputs the data processing result to the output unit 205. The arithmetic unit 204 controls the actuator 111 and the spindle motor 112 of the optical pickup 101 via the communication interfaces 208A and 208B.

  The output unit 205 outputs the data processing result by the calculation unit 204 to the display device 207. The display device 207 displays the data processing result on the screen as characters or graphs.

  The input unit 206 receives data or command input from the outside of the computer 201.

(Outline of software configuration of optical pickup inspection device)
FIG. 6 is a block diagram showing a software configuration of the computer 201 constituting the inspection apparatus 11 of FIG. Viewed functionally, the computer 201 includes a motor drive unit 21 that controls the rotation of the spindle motor 112, an objective lens drive unit 22 that controls the actuator 111 of the optical pickup 101, a storage unit 23, and a waveform extraction unit 30. The extreme value calculation unit 40 and the determination unit 50 are included.

  The storage unit 23 stores the differential push-pull signal DPP digitally converted while the objective lens 107 is repeatedly displaced in the radial direction of the optical recording medium 106 by the actuator 111 as time series data.

  The waveform extraction unit 30 extracts a low-frequency waveform that changes corresponding to the periodic displacement of the objective lens based on the time series data of the differential push-pull signal DPP stored in the storage unit 23. Specifically, the waveform extraction unit 30 generates a waveform of the difference between the upper and lower envelopes of the time series data as a low frequency waveform. The waveform extraction unit 30 includes an end point setting unit 31, an envelope generation unit 32, and a waveform calculation unit 33. The end point setting unit 31 sets the left and right end points of the envelope for each of the upper and lower envelopes. The envelope generation unit 32 generates each of the upper and lower envelopes by sequentially extracting data points that satisfy a predetermined envelope condition from the time-series data in the positive direction of the time axis starting from the left end point. Furthermore, the envelope generation unit 32 generates each of the upper and lower envelopes by sequentially extracting data points that satisfy a predetermined envelope condition from the time-series data in the negative direction of the time axis starting from the right end point. . The final envelope is obtained by averaging the envelope generated in the time axis positive direction and the envelope generated in the time axis negative direction. Here, the envelope condition means that the slope of a straight line passing through adjacent data points falls within a predetermined range. The waveform calculator 33 outputs the waveform of the difference between the upper and lower envelopes generated by the envelope generator 32 as a low frequency waveform.

  The extreme value calculation unit 40 calculates a plurality of minimum values of the low frequency waveform extracted by the waveform extraction unit 30. The extreme value calculation unit 40 includes a sampling waveform generation unit 41, a smoothing unit 42, and a local minimum point extraction unit 43. The sampling waveform generation unit 41 divides the low frequency waveform into a plurality of sections, and generates a sampling waveform composed of the minimum points of the plurality of sections. The smoothing unit 42 generates a smoothed waveform obtained by moving and averaging the sampling waveform. The minimum point extraction unit 43 extracts a plurality of negative intervals in which the value obtained by subtracting the smoothed waveform from the sampling waveform is negative, and extracts the minimum point of the sampling waveform in each of the plurality of negative intervals as a minimum point of the low-frequency waveform. To do.

  The determination unit 50 determines the arrangement (position and orientation) of the diffraction grating 104 with respect to the semiconductor laser 102 depending on whether or not the variation of the plurality of minimum values of the low-frequency waveform calculated by the extreme value calculation unit 40 is within a predetermined range. Judge the quality of the. The determination unit 50 includes an extreme value classification unit 51 and a comparison unit 52. The extreme value classification unit 51 classifies the plurality of minimum values calculated by the extreme value calculation unit 40 into first and second groups. The comparison unit 52 compares the average value of the plurality of minimum values belonging to the first group with the average value of the plurality of minimum values belonging to the second group, thereby determining whether or not the diffraction grating 104 is disposed with respect to the laser light source 102. Determine.

(Operation of optical pickup inspection device)
Next, the operation of the optical pickup inspection apparatus 11 having the above configuration will be described.

FIG. 7 is a flowchart showing the inspection procedure of the optical pickup inspection apparatus 11.
With reference to FIGS. 5 to 7, in step S <b> 501 of FIG. 7, the computer 201 performs initial setting of the inspection apparatus 11. Specifically, the input unit 206 of the computer 201 includes a sampling rate Srate, a sampling data number Snum, a section data number DSnum, a moving average data number DAvnum, a pass / fail judgment threshold Th, a first upper limit value UL1, and a first lower limit. Value LL1, second upper limit value UL2, second lower limit value LL2, moving average data number EAvnum of envelope, noise removal level Nrej of envelope, end point calculation data number IDnum, end order calculation order Node, etc. Accepts input of parameters. The meaning of each parameter will be described in the processing step in which each parameter is used. Each input parameter is stored in the storage device 203 of the computer in FIG.

  In the first embodiment, the value of each parameter is specifically set as follows. Sampling rate Rate = 1200 Hz, sampling data number Snum = 1800, interval data number DSnum = 50, moving average data number DAvnum = 11, pass / fail judgment threshold Th = 0.05, first upper limit value UL1 = 0.1, first 1 lower limit value LL1 = −0.1, second upper limit value UL2 = 0.06, second lower limit value LL2 = −0.06, moving average data number EAvnum = 60 of envelope, envelope The noise removal level Nrej = 1.2, the end point calculation data number IDnum = 20, the end point calculation designation order Node = 8.

  In the next step S502, the objective lens driving unit 22 of the computer 201 controls the actuator 111 in FIG. 1 to move the objective lens 107 to the inner peripheral side and the outer peripheral side in the radial direction of the optical recording medium 106 (the direction across the track). Displace repeatedly between the sides. The computer 201 digitally converts the differential push-pull signal DPP obtained at this time by the AD conversion unit 202 and obtains it as time-series data. At this time, the AD conversion unit 202 samples the differential push-pull signal DPP at the above-described sampling rate Srate. As a result, time-series data of the sampling data number Snum is generated. Here, the sampling rate Srate is set to a frequency that can sufficiently reproduce the change of the differential push-pull signal DPP that is the original signal.

  In the next step S <b> 503, the computer 201 stores the time series data digitally converted by the AD conversion unit 202 in the storage device 203.

  In the next step S504, the waveform extraction unit 30 of the computer 201 generates upper and lower envelopes of the time series data. In the next step S505, the waveform extraction unit 30 generates a low frequency waveform that is the difference between the upper and lower envelopes. Detailed procedures of steps S504 and S505 will be described later with reference to FIGS.

  In the next step S506, the extreme value calculation unit 40 of the computer 201 calculates a plurality of minimum values of the low frequency waveform. The detailed procedure of step S506 will be described later with reference to FIGS.

  In the next step S507, the determination unit 50 of the computer 201 determines whether the diffraction grating 104 with respect to the semiconductor laser 102 depends on whether the variation of the plurality of minimum values of the low-frequency waveform calculated in step S506 is within a predetermined range. The quality of the position and posture is determined. The detailed procedure of step S506 will be described later with reference to FIG. The inspection procedure by the optical pickup inspection apparatus 11 is thus completed.

(Generation of Envelope—Step S504 in FIG. 7)
FIG. 8 is a diagram illustrating an example of the time-series data 320 output from the AD conversion unit 202. In FIG. 8, the X axis indicates the time axis, and the Y axis indicates the strength of the differential push-pull signal DPP. In the actual time series data 320, there is a locally protruding noise signal 83 in addition to a signal whose amplitude periodically changes including a plurality of peak portions 81 and valley portions 82A and 82B. Therefore, the waveform extraction unit 30 in FIG. 6 generates an envelope of the time series data 320 so as not to be affected by the noise signal 83 by the method described below.

  FIG. 9 is a flowchart showing in more detail the procedure of step S504 of FIG. Hereinafter, a procedure for generating the upper envelope (upper envelope) of the time-series data 320 will be described with reference to FIGS. 10 to 15 together with the flowchart of FIG.

  In step S601 in FIG. 9, the waveform extraction unit 30 of the computer 201 in FIG. 6 performs initial setting. The setting values required for calculating the envelope are the first upper limit value UL1, the first lower limit value LL1, the second upper limit value UL2, the second lower limit value LL2, and the moving average data of the envelope There are eight numbers: an EAvnum, an envelope noise removal level Nrej, an end point calculation data number IDnum, and a specified order Node for end point calculation. In the first embodiment, the following values are used. First upper limit value UL1 = 0.1, first lower limit value LL1 = −0.1, second upper limit value UL2 = 0.06, second lower limit value LL2 = −0.06, Envelope moving average data number EAvnum = 60, envelope noise removal level Nrej = 1.2, end point calculation data number IDnum = 20, end point calculation designation order Node = 8. These values are all input in step S501 in FIG.

  In the next step S602, the end point setting unit 31 of the waveform extraction unit 30 in FIG. 6 sets the left and right end points of the upper envelope. The end point is a starting point for performing the process of extracting the upper envelope from the time series data of the number of sampling data Snum. In the following description, the coordinates of the left end point are (Xinit, Yinit).

  Specifically, the end point setting unit 31 is the eighth among the Snum pieces of sampling data, which is the end point calculated data number IDnum counting from the oldest data point, which is the eighth in the specified order. A large value is set as an initial value Yinit for extracting the upper envelope in the positive direction of the time axis. Since the largest value among the sampling data of the endpoint calculation data number IDnum is highly likely to be affected by noise, it is desirable that the designation order Node for endpoint calculation is 2 or more. In the first embodiment, the specified order Noder is set to 8 so that the influence of noise can be suppressed even if the number of points affected by noise is 7 in the 20 sampling data as the endpoint calculation data number IDnum. Is set.

  Similarly for the right end point, among the Snum sampled data, among the number of end point calculated data numbers IDnum counted from the newest data point, the largest value in the specified order Norder is enveloped upward in the time axis. The initial value for extracting the line is used.

  Next, in step S603 of FIG. 9, the envelope generation unit 32 of FIG. 6 starts from the left end point (Xinit, Yinit) and sequentially selects an upper envelope candidate that satisfies the envelope condition in the positive direction of the time axis. Are extracted from the time-series data 320.

  FIG. 10 is a diagram for explaining the processing procedure of step S603 of FIG. In FIG. 10, the first 14 data points A to N of the time series data 320 are schematically shown. In FIG. 10, the left side is data that is temporally old, and the right side is data that is temporally new. A point 301 in the figure is an end point (Xinit, Yinit) of the envelope set by the end point setting unit 31 in FIG.

  In the case of FIG. 10, the envelope generating unit 32 starts from the end points (Xinit, Yinit) and sequentially refers to points in the positive direction of the time axis as point B, point C, point D, point E,. The point that satisfies the envelope condition is set as the next candidate point of the upper envelope. Here, the envelope condition means that the slope of a straight line passing through adjacent data points among the data points of the upper envelope is within a predetermined range. That is, when the current candidate point is the end point (Xinit, Yinit), the next candidate point (Xn, Yn) that satisfies the envelope condition is determined using the first lower limit value LL1 and the first upper limit value UL1. It is given by the following equation (4).

LL1 × (Xn−Xinit) ≦ Yn−Yinit ≦ UL1 × (Xn−Xinit) (4)
The first upper limit value UL1 and the first lower limit value LL1 in the above expression mean the upper limit and the lower limit of the data change amount (slope) per data in the time axis direction, respectively. FIG. 10 shows an upper limit range 302 and a lower limit range 303 that satisfy the above-described envelope condition.

Specifically, Yinit = 3.0, Y coordinate value YB of point B (X coordinate: XB, Y coordinate: YB) is 1.0, and Y coordinate of point C (X coordinate: XC, Y coordinate: YC) Let YC be 3.1. In the case of point B,
LL1 × (XB-Xinit) = − 0.1 × 1 = −0.1
YB-Yinit = 1.0-3.0 = -2.0
UL1 × (XB-Xinit) = 0.1 × 1 = 0.1
Thus, the above formula (4) is not satisfied. As described above, when the next candidate point of the upper envelope is extracted, the envelope generation unit 32 causes the slope between the current candidate point of the upper envelope and the next candidate point to be lower than the first lower limit value LL1. This point is not considered as an envelope candidate point.

On the other hand, in the case of point C,
LL1 × (XC-Xinit) = − 0.1 × 2 = −0.2
YB-Yinit = 3.1-3.0 = 0.1
UL1 × (XC-Xinit) = 0.1 × 2 = 0.2
Thus, the above formula (4) is satisfied. Therefore, the point C becomes an envelope candidate point.

  Subsequently, the envelope generation unit 32 searches for the next upper envelope candidate point in the positive direction of the time axis with reference to the point C, which is the current upper envelope candidate point. At this time, since the points D, E, and F are below the lower limit range 303C with respect to the point C, they are not candidate points for the upper envelope. Since the point G is within the upper limit range 302C and the lower limit range 303C with respect to the point C and satisfies the envelope condition, it becomes the next candidate point for the upper envelope.

  Subsequently, the envelope generation unit 32 searches for the next upper envelope candidate point in the positive direction of the time axis with reference to the point G that is the current upper envelope candidate point. At this time, since the point H is below the lower limit range 303G with respect to the point G, it is not a candidate point for the upper envelope. On the other hand, the point I exceeds the upper limit range 302G with respect to the point G. Here, when the envelope generation unit 32 exceeds the range satisfying the envelope condition (between the lower limit range 303G and the upper limit range 302G), the upper limit point Ia of the range satisfying the envelope condition is set as the upper envelope point. Candidate points.

  Subsequently, the envelope generation unit 32 searches for a next upper envelope candidate point in the positive direction of the time axis with reference to the point Ia which is the current upper envelope candidate point. At this time, the point J is less than the lower limit range 303Ia with the point Ia as a reference, and thus is not a candidate point for the upper envelope. On the other hand, the point K is between the lower limit range 303Ia and the upper limit range 302Ia with the point Ia as a reference and satisfies the envelope condition, and is therefore a candidate for the next upper envelope.

  Subsequently, the envelope generation unit 32 searches for the next candidate point of the upper envelope in the positive direction of the time axis with reference to the point K, which is the current candidate point of the upper envelope. At this time, since the points L and M are below the lower limit range 303K with respect to the point K, they are not candidate points for the upper envelope. On the other hand, the point N is between the lower limit range 303K and the upper limit range 302K with the point K as a reference, and satisfies the envelope condition, so becomes the next upper envelope candidate.

  In this way, the end point 301 and the points C, G, Ia, K, and N are extracted as candidate points for the upper envelope. Here, the envelope values corresponding to the X coordinates (time) of the points B, D, E, F, H, J, L, and M that have not become candidates for the upper envelope are the latest before and after each point. A value on a straight line passing through the envelope candidate points is set as an envelope value corresponding to each X coordinate (time). For example, a point on the upper envelope corresponding to the X coordinate (time) of the point E is given as an intersection of a straight line passing through the point E and parallel to the Y axis and the straight line CG. Thereby, the same number of candidate points of the upper envelope 321A as the number of sampling data Snum are generated.

  Next, in step S604 in FIG. 9, the envelope generation unit 32 in FIG. 6 starts from the right end point set in step S602 and sets data points that are candidates for the upper envelope in the negative direction of the time axis as time-series data. Extract from 320. In step S604, processing similar to that in step S603 is performed in the opposite direction on the time axis.

  FIG. 11 is a diagram for explaining the processing procedure of step S604 of FIG. FIG. 11 schematically shows the first 14 data points A to N of the time-series data 320, as in FIG. In FIG. 11, the left side is data that is temporally old, and the right side is data that is temporally new.

  In FIG. 11, it is assumed that a point N is extracted as a candidate point for the current upper envelope. The envelope generation unit 32 searches for a candidate point for the next upper envelope in the negative direction of the time axis with respect to the point N. At this time, since the points M and L are below the lower limit range 305N with respect to the point N, they are not candidates for the upper envelope. On the other hand, the point K is between the lower limit range 305N and the upper limit range 304N with the point N as a reference, and satisfies the envelope condition, so becomes the next upper envelope candidate.

  Subsequently, the envelope generation unit 32 searches for the next candidate point of the upper envelope in the negative direction of the time axis with reference to the point K that is the current candidate point of the upper envelope. At this time, since the point I exceeds the range that satisfies the envelope condition with respect to the point K (between the lower limit range 305K and the upper limit range 304K), the point Ib is higher than the upper limit point Ib of the range that satisfies the envelope condition. Let it be the next candidate point of the envelope.

  Subsequently, the envelope generation unit 32 searches for the next candidate point of the upper envelope in the negative direction of the time axis with reference to the point Ib which is the current candidate point of the upper envelope. At this time, since the points H, G, F, E, and D are below the lower limit range 305Ib with respect to the point Ib, they are not candidate points for the upper envelope. On the other hand, the point C is between the lower limit range 305Ib and the upper limit range 304Ib with the point Ib as a reference and satisfies the envelope condition, and is therefore a candidate for the next upper envelope.

  Subsequently, the envelope generation unit 32 searches for a candidate point of the next upper envelope in the negative direction of the time axis with reference to the point C that is the current candidate point of the upper envelope. At this time, since the point B is below the lower limit range 305C with respect to the point C, it is not a candidate point for the upper envelope. On the other hand, the point A is between the lower limit range 305C and the upper limit range 304C with the point C as a reference, and satisfies the envelope condition, so becomes the next upper envelope candidate.

  In this way, the points N, K, Ib, C, and A in FIG. 11 are extracted as candidate points for the upper envelope. Here, the envelope values corresponding to the X coordinates (time) of the points B, D, E, F, G, H, J, L, and M that are not candidates for the upper envelope are before and after each point. The value of the point on the straight line passing through the most recent envelope candidate point is the envelope value corresponding to each X coordinate (time). For example, a point on the envelope corresponding to the X coordinate (time) of the point E is given as an intersection of a straight line passing through the point E and parallel to the Y axis and the straight line CIb. Thereby, the same number of candidate points of the upper envelope 321B as the number of sampling data Snum are generated.

  Hereinafter, the procedure of steps S603 and S604 of FIG. 9 described with reference to FIGS. 10 and 11 will be summarized with reference to FIG.

  FIG. 12 is a flowchart showing the procedure of steps S603 and S604 of FIG. FIG. 12 shows a procedure from the current candidate point (Xo, Yo) to the next candidate point (Xn, Yn) being set. Note that there is a difference between step S603 and step S604 in FIG. 9 in which the next data point is acquired in the time axis positive direction or the next data point is acquired in the time axis negative direction in the following step S632.

  In step S631 in FIG. 12, it is assumed that the envelope generation unit 32 in FIG. 6 has extracted the current candidate point (Xo, Yo) of the upper envelope.

  In the next step S632, the envelope generation unit 32 determines the current candidate point (Xo, Yo) from the time-series data 320 of the differential push-pull signal DPP in the time axis positive direction (in the negative direction in step S604). The next data point (Xn, Yn) is acquired.

  In the next step S633, the envelope generation unit 32 uses the current candidate point (Xo, Yo) as a reference, and the lower limit in which the data point (Xn, Yn) acquired in step S632 is defined by the lower limit value LL1. It is determined whether or not the range is exceeded. That is, the envelope generation unit 32 determines whether or not the data point (Xn, Yn) satisfies the following equation (5).

LL1 × | Xn−Xo | ≦ Yn−Yo (5)
If the above equation (5) is not satisfied (NO in step S633), the envelope generation unit 32 returns the process to step S632, and further sets the next data point in the time axis positive direction (in the negative direction in the case of step S604). (Xn, Yn) is acquired. Thereafter, in step S633, the envelope generation unit 32 determines whether or not the above equation (5) is satisfied for the newly acquired data point.

  If the above equation (5) is satisfied (YES in step S633), step S634 is then executed. In step S634, the envelope generation unit 32 uses the current candidate point (Xo, Yo) as a reference, and the upper limit range in which the data point (Xn, Yn) acquired in step S632 is defined by the upper limit value UL1. It is determined whether or not: That is, the envelope generation unit 32 determines whether or not the data point (Xn, Yn) satisfies the following equation (6).

Yn−Yo ≦ UL1 × | Xn−Xo | (6)
If the above equation (6) is satisfied (YES in step S634), step S635 is then executed. In step S635, the envelope generation unit 32 sets the data point (Xn, Yn) acquired in step S632 as a candidate for the next upper envelope, and each procedure in FIG. 12 ends.

  On the other hand, if the above equation (6) is not satisfied (NO in step S634), the process proceeds to step S636. In step S636, the envelope generation unit 32 sets the upper limit point (Xn, UL1 × | Xn−Xo |) that satisfies the above equation (6) as a candidate for the next upper envelope, and each procedure in FIG. finish.

  Referring to FIG. 9 again, in step S605, envelope generation unit 32 in FIG. 6 averages the envelope extraction result in step S603 and the envelope extraction result in step S604.

  FIG. 13 is a diagram for explaining the processing procedure of step S605 of FIG. FIG. 13 schematically shows the first 14 data points A to N of the time-series data 320 as in FIGS. 10 and 11. In addition, the upper envelope 321A generated in step S603 and the upper envelope 321B generated in step S604 are also shown in the drawing.

  Specifically, the envelope generation unit 32 corresponds to each X coordinate (time) of the time series data 320 of the sampling data number Snum, and the candidate point of the envelope 321A in step S603 and the envelope 321B in step S604. An average value 321C with the candidate points is calculated. The calculated average value 321C is indicated by a circle in the figure.

  Next, in step S606 in FIG. 9, the envelope generation unit 32 in FIG. 6 performs a smoothing process in the time axis direction on the data averaged in step S605 (reference numeral 321C in FIG. 13). At this time, the smoothing process is performed by moving average. In the case of Embodiment 1, a moving average is calculated using EAvnum data before and after each data point of the envelope. Here, the moving average data number EAvnum is initially set to 60 in step S601. However, in the case of the left end point of the envelope, the moving average is calculated using the point after the left end point, and in the case of the right end point of the envelope, the moving average is used using the point before the right end point. Is calculated.

  In the next step S607, the envelope generator 32 of FIG. 6 uses the upper envelope generated in the previous step S606 to generate the time series data 320 of the differential push-pull signal DPP that is the input data of the computer 201. To remove noise. That is, the envelope generation unit 32 removes, from the time series data 320, data points that exceed a predetermined threshold and deviate from the upper envelope from among the data points of the first time series data 320.

  FIG. 14 is a diagram for explaining the processing procedure of step S607 of FIG. FIG. 14 schematically shows the first 14 data points A to N of the time-series data 320 as in the case of FIGS. 10 to 13. Also shown is the upper envelope 321D smoothed by step S606. Of the data points A to N, a point I that greatly exceeds the smoothed upper envelope 321D is a noise removal target point.

  Specifically, the envelope generation unit 32 calculates the ratio between the Y coordinate of each data point A to N and the value of the upper envelope 321D in the X coordinate of each data point A to N, and the value of the calculated ratio However, data points exceeding the noise removal level Nrej set in step S601 are targeted for noise removal. For example, the value of the Y coordinate of the point I in FIG. 14 is set to 6.5, and the value of the upper envelope 321D at the X coordinate XI of the point I is set to 5.0. Since the ratio between the two is 6.5 / 5.0 = 1.3, it exceeds the noise removal level Nrej = 1.2. As a result, the point I in FIG. 14 is a target for noise removal.

  Next, a method for removing the point I in FIG. 14 as noise will be described. When the point I is removed, when the upper envelope is searched for in the positive direction of the time axis in the above-described step S603, the point G that is a candidate point for the upper envelope one point before the point I and the time axis in the step S604 When the upper envelope is searched in the negative direction, attention is paid to a point K that is a candidate point for the upper envelope one point before point I. The envelope generation unit 32 compares the lower limit range 303G with respect to the point G with the lower limit range 305K with respect to the point K, and the lower limit range with the smaller value at the X coordinate XI of the point I 305K is selected, and a point Ic smaller than the lower limit range 305K is set as a point to replace the point I. The newly set point Ic becomes smaller than the lower limit range when the upper envelope is extracted again in steps S608 and S609, which will be described later, and thus is not a candidate for the upper envelope.

  Next, in step S608 in FIG. 9, the envelope generation unit 32 in FIG. 6 performs an upper envelope in the time axis positive direction with respect to the time series data 320 of the differential push-pull signal DPP after noise removal in step S607. Re-extract the line. The process of step S608 is basically the same as the process of step S603, except that the input signal is time-series data 320 after noise removal, and the first upper limit value UL1 and the first lower limit value LL1. Instead of step S603, the second upper limit value UL2 and the second lower limit value LL2 are used instead. Other processing in step S608 is similar to the processing in step S603, and therefore description thereof will not be repeated.

  In the next step S609, the envelope generation unit 32 in FIG. 6 extracts the upper envelope in the time axis negative direction from the time series data 320 of the differential push-pull signal DPP after noise removal in step S607. Do. The processing in step S609 includes the point that the input signal is time-series data 320 after noise removal, the second upper limit value UL2 and the second upper limit value UL1 instead of the first upper limit value UL1 and the first lower limit value LL1. Is different from the process of step S604 in that the lower limit value LL2 is used. The other processes in step S609 are the same as the processes in step S604, and therefore description thereof will not be repeated.

  In the next step S610, the envelope generation unit 32 in FIG. 6 averages the envelope extraction result in step S608 and the envelope extraction result in step S609. Since the specific processing content is the same as the processing content of step S605, description will not be repeated.

  In the next step S611, the envelope generation unit 32 in FIG. 6 performs a smoothing process in the time axis direction on the data averaged in step S610. Since the specific processing content is the same as the processing content in step S606, the description will not be repeated.

  In the next step S612, the processing result of step S611 is output, and the process of generating the upper envelope is terminated.

  Thereafter, the waveform extraction unit 30 in FIG. 6 generates a lower envelope for the time series data 320 of the differential push-pull signal DPP. The procedure for generating the lower envelope is the same as the process of inverting the Y axis in the procedure for generating the upper envelope described so far, and therefore description thereof will not be repeated.

  FIG. 15 is a diagram showing upper and lower envelopes 321 and 322 generated based on the time-series data 320 shown in FIG. By generating the upper and lower envelopes 321 and 322 according to the above procedure, the envelopes 321 and 322 of the time-series data 320 can be generated without being influenced by the plurality of noise signals 83 protruding vertically.

(Generation of Low Frequency Waveform—Step S505 in FIG. 7)
FIG. 16 is a diagram showing a low-frequency waveform 323 generated from the upper and lower envelopes 321 and 322 in FIG. The low frequency waveform 323 corresponds to the first waveform of the present invention.

  As described with reference to FIGS. 4A to 4C, in the optical pickup inspection apparatus 11 according to the first embodiment, the objective lens 107 is controlled based on the time-series data of the differential push-pull signal DPP. A waveform of a frequency component (low frequency waveform) that changes corresponding to the displacement is extracted. At this time, although it is conceivable to use a frequency analysis method such as Fourier analysis, if calculation such as fast Fourier transform is performed, it will take time due to signal analysis, and adjustment of the optical pickup in a short time becomes difficult. . Therefore, the optical pickup inspection apparatus 11 according to the first embodiment extracts a low-frequency waveform using the envelope of the time series data of the differential push-pull signal DPP. Specifically, as illustrated in FIG. 16, the waveform calculation unit 33 in FIG. 6 generates a waveform of a difference between the upper envelope 321 and the lower envelope 322 as a low frequency waveform 323.

  Note that the low-frequency waveform calculation method using the upper and lower envelopes differs depending on the characteristics of the original time-series data. In the case of the differential push-pull signal DPP, it is optimal to calculate the difference between the upper and lower envelopes as a low frequency waveform, but depending on the input signal waveform, the average or sum of the upper and lower envelopes may be reduced. In some cases, it is best to output as a frequency waveform.

  As one guideline, as shown in FIG. 15, when the upper envelope 321 and the lower envelope 322 of the input signal waveform are in reverse phase, that is, when the upper envelope 321 is a mountain, the lower envelope 322 becomes a valley, When the upper envelope 321 is a valley and the lower envelope 322 is a mountain, the difference between the upper envelope 321 and the lower envelope 322 is output as a low frequency waveform 323 as shown in FIG. Is preferred. On the other hand, when the upper envelope 329 and the lower envelope 330 are in phase as in time series data 328 of the main push-pull signal MPP described later in FIG. 27, that is, when the upper envelope 329 is a mountain, the lower envelope 330 is also When the upper envelope 329 is a valley and the lower envelope 330 is also a valley, it is preferable to output the average or sum of the upper envelope and the lower envelope as the low-frequency waveform 331. Alternatively, when the shape of the upper envelope and the shape of the lower envelope are similar, either one of the envelopes may be output as the low frequency waveform 331. In this way, the waveform of the frequency component (low frequency waveform) that changes in response to the displacement of the objective lens 107 is either one of the upper and lower envelopes, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes. It is a waveform based on.

(Calculation of local minimum value-step S506 in FIG. 7)
FIG. 17 is a flowchart showing in more detail the procedure of step S506 of FIG. Hereinafter, a procedure for calculating a plurality of minimum values of the low-frequency waveform 323 will be described with reference to FIGS. 18 to 21 together with the flowchart of FIG. In the first step S551 in FIG. 17, the sampling waveform generation unit 41 in FIG. 6 generates a sampling waveform from the low frequency waveform 323.

  FIG. 18 is a diagram for explaining the processing procedure of step S551 in FIG. Referring to FIG. 18, the sampling waveform generation unit 41 in FIG. 6 divides the low frequency waveform 323 into a plurality of sections for each section data number DSnum. In the case of the first embodiment, 50 is input in advance as the section data number DSnum in step S501 of FIG. Then, the sampling waveform generation unit 41 calculates a point having a minimum value (ie, the minimum point) for each of the 50 data points in each section, and generates the sampling waveform by arranging the minimum points in time series. To do.

  FIG. 19 is a diagram showing the sampling waveform 324 generated in step S551 in FIG. The shape of the sampling waveform 324 is substantially the same as that of the low frequency waveform 323, but the number of data of the sampling waveform 324 is 1 / DSnum of the number of data Sunm of the low frequency waveform 323.

  Next, in step S552 in FIG. 17, the smoothing unit 42 in FIG. 6 generates a smoothed waveform (reference numeral 325 in FIG. 20) obtained by smoothing the sampling waveform 324 generated in step S551. The smoothing process at this time is performed by moving average. In the first embodiment, a moving average is calculated using DAvnum pieces of data before and after each data point of the sampling waveform 324. Here, the moving average data number DAvnum is initially set to 11 in step S501. However, in the case of the left end point of the sampling waveform 324, the moving average is calculated using the point at the time after the left end point, and in the case of the right end point of the sampling waveform 324, the point at the time before the right end point is used. A moving average is calculated.

  Next, in step S553 in FIG. 17, the local minimum point extraction unit 43 in FIG. 6 extracts the position of the local minimum point in the sampling waveform 324 calculated in step S552. The minimum point at this time is a point corresponding to the valley of the differential push-pull signal DPP. Depending on how the low frequency waveform 323 is defined, for example, when the sign of the low frequency waveform 323 is inverted from the above case, it is necessary to extract the maximum point of the sampling waveform 324.

  FIG. 20 is a diagram for explaining the processing procedure of step S553 of FIG. Referring to FIG. 20, the minimum point extraction unit 43 in FIG. 6 compares the sampling waveform 324 and the smoothed waveform 325, and a plurality of sections in which the value obtained by subtracting the smoothed waveform 325 from the sampling waveform 324 is negative. (Referred to as negative interval). In the case of FIG. 20, the negative interval is the interval [S1, T1], [S2, T2],..., [S5, T5], and the point Si (i is an integer) where the sampling waveform 324 falls below the smoothing waveform 325. To the point Ti (i is an integer) where the sampling waveform 324 again exceeds the smoothing waveform 325. It is estimated that there is a minimum point of the sampling waveform 324 in each of the plurality of negative intervals [Si, Ti]. Therefore, the minimum point extraction unit 43 extracts the minimum point of each negative section [Si, Ti] as the position of the minimum point. In the example of FIG. 20, five minimum points from V1 to V5 are extracted.

  Next, in step S554 in FIG. 17, the position of the minimum point on the low frequency waveform 323 corresponding to the positions of the minimum points V1 to V5 of the sampling waveform 324 extracted in step S553 is determined. In the first embodiment, the minimum point of the sampling waveform 324 corresponds to the minimum point of a section data number DSnum (= 50 points) on the low frequency waveform 323. Therefore, the minimum point of the sampling waveform 324 becomes the minimum point on the low frequency waveform 323.

  FIG. 21 is a diagram showing the positions of the minimum points V1 to V5 determined on the low frequency waveform 323. FIG. This completes the step of extracting the minimum point of the low-frequency waveform 323 shown in FIG.

(Optical Pickup Pass / Fail Judgment—Step S507 in FIG. 7)
FIG. 22 is a flowchart showing in more detail the procedure of step S507 of FIG. 6 determines the arrangement (position and position) of the diffraction grating 104 with respect to the laser light source 102 in FIG. 1 from the variation in the positions of the minimum points V1 to V5 on the low-frequency waveform 323 calculated in step S506 in FIG. (Position) is judged as good or bad.

  First, in step S651 in FIG. 22, the extreme value classification unit 51 in FIG. 6 classifies the plurality of local minimum points calculated by the extreme value calculation unit 40 into first and second groups. In the case of the first embodiment, the extreme value classification unit 51 classifies the plurality of minimum points V1 to V5 alternately into the first and second groups in time series order. In the case of FIG. 21 described above, the minimum points V1, V3, and V5 are classified into the first group, and the minimum points V2 and V4 are classified into the second group. The reason for this classification is as follows.

  In the optical pickup inspection apparatus 11 according to the first embodiment, the differential push-pull signal DPP is detected when the objective lens 107 in FIG. 1 is repeatedly displaced toward the inner and outer peripheral sides of the optical recording medium 106 in the radial direction. Is done. In this case, the amplitude of the time series data of the differential push-pull signal DPP periodically varies, and the amplitude trough when the objective lens 107 is shifted to the inner peripheral side and the amplitude when the objective lens 107 is shifted to the outer peripheral side. No valleys appear alternately. Therefore, by alternately classifying a plurality of minimum points of the low frequency waveform in time series order, the amplitude of the differential push-pull signal DPP when the objective lens 107 is shifted to the inner peripheral side, and the objective lens 107 to the outer peripheral side. It becomes possible to classify into the amplitude of the differential push-pull signal when shifted.

  Next, in step S652 of FIG. 22, the comparison unit 52 of FIG. 6 calculates the average value of the minimum point values (minimum values) for each of the first and second groups. Then, in the next step S653, the comparison unit 52 determines whether or not the ratio of the average values for each group is within a predetermined range. Specifically, the comparison unit 52 performs diffraction when the absolute value of the difference between the average value ratio and 1 is equal to or less than the pass / fail judgment threshold Th (Th = 0.05) input in step S501 of FIG. It is determined that the arrangement of the lattice is good, and is determined to be defective if it exceeds the pass / fail judgment threshold Th. This is the end of the procedure for determining the quality of the arrangement of the diffraction grating 104.

(Summary)
As described above, according to the optical pickup inspection apparatus 11 of the first embodiment, variations in the values (minimum values) of the minimum points V1 to V5 of the low-frequency waveform 323 extracted from the time series data of the differential push-pull signal DPP. By the evaluation, the optical pickup 101 can be inspected with high accuracy. As a result, variation in the adjustment of the position and orientation of the diffraction grating 104 can be suppressed, the adjustment time can be shortened, and labor costs and the like can be reduced.

  Specifically, the waveform of the difference between the upper and lower envelopes 321 and 322 of the time series data 320 of the differential push-pull signal DPP is changed to a waveform of a frequency component that changes in accordance with the periodic displacement of the objective lens 107 (low Frequency waveform) 323.

  Further, when the upper and lower envelopes 321 and 322 are generated from the time series data, the slope of the straight line passing through the adjacent points is between the first upper limit value UL1 and the first lower limit value LL1. Since changes in the amplitudes of the envelopes 321 and 322 are limited, the envelopes 321 and 322 can be generated while suppressing the influence of noise even when the noise signal 83 is included in the time-series data.

  Further, when generating the upper and lower envelopes 321 and 322 from the time series data, the envelope generated in the time axis positive direction and the envelope generated in the time axis negative direction are averaged and further averaged. Since the final envelope is generated by smoothing the envelopes by moving average, the envelopes 321 and 322 can be generated with high accuracy even if the original time-series data includes a noise component.

  Also, once the upper and lower envelopes are generated, the data points that exceed the noise removal level Nrej and deviate from the upper and lower envelopes in the time series data are removed as noise, and the time series data after noise removal is Since the envelope is generated again by using the envelope, the envelope can be generated with higher accuracy.

  In addition, the end points of the envelopes, which are the starting points when extracting the upper and lower envelopes 321 and 322, are set avoiding specific data points such as the beginning or end of time series data, thus eliminating the influence of noise. Thus, the calculation accuracy of the envelope can be increased.

  Further, when extracting the minimum points V1 to V5 of the low frequency waveform 323, the minimum points V1 to V5 are extracted using the sampling waveform 324 in which the number of data of the low frequency waveform 323 is reduced, so that the original low frequency waveform 323 is extracted. Therefore, it is possible to extract the local minimum points V1 to V5 with high accuracy. Further, since the minimum points V1 to V5 are extracted using the sampling waveform 324 in which the number of data is reduced, the processing time of the computer can be shortened. Further, since the minimum points V1 to V5 are extracted using the smoothed waveform 325 obtained by smoothing the sampling waveform 324 by moving average, the minimum points V1 to V5 can be accurately obtained even when the amplitude of the low frequency waveform 323 is significantly changed. Can be detected. As a result, the accuracy of the quality determination by the determination unit 50 can be improved.

  Further, the determination unit 50 classifies the plurality of minimum points V1 to V5 when the objective lens 107 is shifted to the inner peripheral side of the optical recording medium 106 and when the objective lens 107 is shifted to the outer peripheral side. By comparing the average value of the point values (minimum values), the quality of the optical pickup 101 can be determined with high accuracy.

(Comparison with conventional technology)
Hereinafter, the envelope generation method and the extreme value calculation method in the first embodiment will be compared with the conventional method.

  FIG. 23 is a diagram illustrating an example of the differential push-pull signal. In FIG. 23, the X axis represents the time axis, and the Y axis represents the intensity of the differential push-pull signal. In the method shown in the first embodiment, an envelope that is an outline of a signal waveform is obtained in order to calculate the amplitudes of the three arrow portions (1001, 1002, 1003) in the figure of the differential push-pull signal. After that, the amplitude is calculated by specifying the position of the minimum or maximum point of the envelope.

  The first prior art disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2007-209882 (Patent Document 2) also uses an envelope for signal waveform analysis, but the method for calculating the envelope is different from that in the first embodiment. In the case of the first prior art, when generating the upper envelope, the local maximum points of the input signal waveform are calculated, and the interpolation between the calculated local maximum points is performed by linear interpolation or cubic spline method. An envelope is generated. Further, when generating the lower envelope, the local minimum point of the input signal waveform is calculated, and the lower envelope is generated by performing interpolation between the calculated local minimum points by linear interpolation or cubic spline method. Yes.

  For this reason, if the upper and lower envelopes of the differential push-pull signal in FIG. 23 are calculated using the first conventional technique, it is affected by local noise (1004, 1005, 1006) in FIG. Become. Further, since the local maximum point is used, the valley portion (near the minimum point) 1007 of the upper envelope cannot be accurately traced. Similarly, since the local minimum point is used for the lower envelope, the peak (near the maximum point) 1008 of the lower envelope cannot be accurately traced. On the other hand, in the case of the first embodiment, since the upper and lower envelopes are accurately traced while suppressing the influence of noise, an accurate envelope can be obtained.

  According to the second prior art disclosed in Japanese Patent Application Laid-Open No. 2004-79079 (Patent Document 3), the maximum point is determined by determining that the change in the value of the tracking error signal has shifted from an increasing trend to a decreasing trend. Is detected. Further, the minimum point is detected by determining that the change in the value of the tracking error signal has shifted from a decreasing tendency to an increasing tendency. Furthermore, in the second prior art, the number of peaks detected between zero cross points is limited to one in order to reduce the possibility of false detection of false peaks in a tracking error signal with large noise.

  Therefore, when the local maximum point and the local minimum point of the waveform shown in FIG. 24 are detected using the second prior art, only one of the local maximum points 1011 is detected, and the local minimum point 1012 and the local maximum point 1013 cannot be detected. There is. On the other hand, in the case of the first embodiment in which the maximum point and the minimum point are extracted by comparing with the smoothed waveform, the position of the maximum point and the minimum point can be accurately obtained.

[Modification of Embodiment 1]
Hereinafter, as a modification of the first embodiment, a method for obtaining the maximum point of the low-frequency waveform 323 in FIG. 16 will be supplemented. When obtaining the maximum point of the low-frequency waveform 323, the calculation is performed according to the steps of FIG.

  First, in step S551 in FIG. 17, the sampling waveform generation unit 41 in FIG. 6 generates a sampling waveform from the low frequency waveform 323. At this time, as shown in FIG. 18, the sampling waveform generation unit 41 in FIG. 6 divides the low frequency waveform 323 into a plurality of sections for each section data number DSnum. Then, the sampling waveform generation unit 41 calculates a point having the maximum value (ie, the maximum point) for each of the 50 data points in each section, and generates the sampling waveform by arranging the maximum points in time series. To do.

  FIG. 25 is a diagram showing the sampling waveform 326 generated in step S551 in FIG. The shape of the sampling waveform 326 in FIG. 25 is almost the same as that of the sampling waveform 324 in FIG. 19, but in the case of FIG. 19, the sampling waveform is generated by the minimum point in each section of FIG. In the case of 25, a sampling waveform is generated by the maximum point of each section in FIG.

  Next, in step S552 in FIG. 17, the smoothing unit 42 in FIG. 6 generates a smoothed waveform (reference numeral 327 in FIG. 26) obtained by smoothing the sampling waveform 326 generated in step S551. The smoothing process at this time is performed by moving average. In the modification of the first embodiment, a moving average is calculated using DAvnum pieces of data before and after each data point of the sampling waveform 326. Here, the moving average data number DAvnum is initially set to 11 in step S501. However, in the case of the left end point of the sampling waveform 326, the moving average is calculated using the point after the left end point, and in the case of the right end point of the sampling waveform 326, the point of the time before the right end point is used. A moving average is calculated.

  Next, in step S553 in FIG. 17, the local maximum point extraction unit 43 in FIG. 6 extracts the position of the local maximum point in the sampling waveform 326 calculated in step S552.

  FIG. 26 is a diagram for explaining the processing procedure of step S553 in FIG. Referring to FIG. 26, the local maximum point extraction unit 43 in FIG. 6 compares the sampling waveform 326 with the smoothed waveform 327, and a plurality of intervals in which the value obtained by subtracting the smoothed waveform 327 from the sampling waveform 326 is positive. (Referred to as a positive interval). In FIG. 26, the positive interval is the interval [P1, Q1], [P2, Q2],..., [P5, Q5], and the point Pi (i is an integer) where the sampling waveform 326 exceeds the smoothed waveform 327. To the point Qi (i is an integer) where the sampling waveform 326 falls below the smoothing waveform 327 again. It is estimated that there is a maximum point of the sampling waveform 326 in each of the plurality of positive intervals [Pi, Qi]. Therefore, the local maximum point extraction unit 43 extracts the maximum point of each positive section [Pi, Qi] as the position of the local maximum point. In the example of FIG. 26, five local maximum points from R1 to R5 are extracted.

  Next, in step S554 in FIG. 17, the position of the local maximum point on the low frequency waveform 323 corresponding to the positions of the local maximum points R1 to R5 of the sampling waveform 326 extracted in step S553 is determined. In the first embodiment, the maximum point of the sampling waveform 326 corresponds to the maximum point of a section data number DSnum (= 50 points) on the low frequency waveform 323. Therefore, the maximum point of the sampling waveform 326 becomes the maximum point on the low frequency waveform 323. Thus, the step of extracting the maximum point of the low frequency waveform 323 shown in FIG. 17 is completed.

[Embodiment 2]
The inspection apparatus 11 according to the first embodiment determines the quality of the arrangement of the diffraction grating 104 in FIG. 1 using only the differential push-pull signal DPP as a tracking error signal. In the case of the second embodiment, the inspection apparatus 11 further determines the quality of the arrangement of the diffraction grating 104 by further using the main push-pull signal MPP in addition to the differential push-pull signal DPP as a tracking error signal. Thereby, the accuracy of the optical pickup quality determination can be further increased.

  Here, the time series data analysis procedure of the main push-pull signal MPP is substantially the same as the time series data analysis procedure of the differential push-pull signal DPP. Therefore, the configuration of the inspection apparatus 11 in FIG. 6 and the flowchart in FIG. 7 are almost the same in the case of the first embodiment and the case of the second embodiment. In the following, different parts from the case of the first embodiment will be mainly described, and description of common parts will not be repeated.

  First, in the case of the second embodiment, in step S503 in FIG. 7, the storage unit 23 in FIG. 6 stores time-series data of the main push-pull signal MPP in addition to the differential push-pull signal DPP.

  Next, in the case of the second embodiment, in step S504 in FIG. 7, the end point setting unit 31 in FIG. 6 further sets the end points of the upper and lower envelopes for the time series data of the main push-pull signal MPP. . Then, the envelope generator 32 further generates upper and lower envelopes for the time series data of the main push-pull signal MPP.

  FIG. 27 is a diagram showing the time series data 328 of the main push-pull signal MPP and the upper and lower envelopes 329 and 330 generated. A specific method of generating envelopes 329 and 330 is the same as that of differential push-pull signal DPP described with reference to FIGS. 9 to 15, and therefore description thereof will not be repeated.

  Next, in the case of the second embodiment, in step S505 in FIG. 7, the waveform calculation unit 33 in FIG. 6 further calculates the average of the upper and lower envelopes of the time series data of the main push-pull signal MPP generated in step S504. Generate a low frequency waveform.

  FIG. 28 is a diagram showing a low-frequency waveform 331 generated from the upper and lower envelopes 329 and 330 in FIG. In the case of the main push-pull signal MPP, since the upper envelope 329 and the lower envelope 330 are in phase, the waveform calculator 33 calculates the average (or sum) waveform of the upper envelope 329 and the lower envelope 330. Is generated as a low-frequency waveform 331. In the case of FIG. 28, since the shape of the upper envelope 329 and the shape of the lower envelope 330 are similar, one of the waveforms can be a low frequency waveform. The low frequency waveform 331 corresponds to the second waveform of the present invention.

  Next, in the case of the second embodiment, in step S506 in FIG. 7, the extreme value calculation unit 40 in FIG. 6 further calculates a minimum point for the low-frequency waveform 331 based on the main push-pull signal MPP. A specific method for calculating the minimum point is the same as that of differential push-pull signal DPP described with reference to FIGS. 17 to 21, and therefore description thereof will not be repeated.

  Next, the determination process in step S507 in FIG. 7 will be described. In the second embodiment, the method of classifying the extreme values of the low-frequency waveform 323 in step S651 in FIG. 22 is different from that in the first embodiment. Steps S652 and S653 in FIG. 22 are the same as those in the first embodiment, and therefore description thereof will not be repeated.

  FIG. 29 is a diagram for explaining a method of classifying a plurality of minimum points of the low-frequency waveform 323 according to the second embodiment. In FIG. 29, the low frequency waveform 323 that is the difference between the upper and lower envelopes of the time series data of the differential push-pull signal DPP and the low frequency waveform that is the average of the upper and lower envelopes of the time series data of the main push-pull signal MPP. 331 is shown. The low frequency waveforms 323 and 331 are displayed with respect to a common time axis (X axis). Also, as shown in FIG. 29, in step S506 of FIG. 7, minimum points Va1 to Va5 are extracted from the low frequency waveform 323, and minimum points Vb1 and Vb2 are extracted from the low frequency waveform 331.

  In the case of the second embodiment, in step S651 of FIG. 22, the extreme value classification unit 51 of FIG. 6 performs the minimal point Va2 of the low-frequency waveform 323 obtained at substantially the same time as the minimal points Vb1 and Vb2 of the low-frequency waveform 331. , Va4 are classified into the first group, and the remaining minimum points Va1, Va3, Va5 are classified into the second group. This effect is as follows.

  As already described, the minimum point of the low frequency waveform 323 is obtained corresponding to the case where the objective lens 107 of FIG. 1 is shifted to the inner and outer peripheral sides of the optical recording medium 106, respectively. Therefore, in the case of the first embodiment, the plurality of minimum points are classified into the first group and the second group alternately in time order.

  However, if the adjustment of the diffraction grating is extremely insufficient or affected by a disturbance, a false peak that does not correspond to the shift of the objective lens 107 in FIG. . In this case, as in the first embodiment, if a method of alternately classifying a plurality of local minimum points into the first group and the second group in time order is used, the local minimum points corresponding to the shift of the objective lens 107 are obtained. Cannot be classified correctly.

  Therefore, in the second embodiment, the extreme value classification unit 51 in FIG. 6 uses the minimum points Vb1 and Vb2 of the low-frequency waveform 331 based on the main push-pull signal MPP, and uses the low-frequency based on the differential push-pull signal DPP. The local minimum points Va1 to Va5 of the waveform 323 are classified into a first group corresponding to the local minimum points Vb1 and Vb2 and a remaining second group. Thereby, the quality determination of the arrangement of the diffraction grating 107 can be performed with higher accuracy than in the first embodiment.

  Unlike the above case, the local minimum points Va1 to Va5 of the low-frequency waveform 323 based on the differential push-pull signal DPP are set to the first using a plurality of maximum points of the low-frequency waveform 331 based on the main push-pull signal MPP. It is also possible to classify into the second group.

[Embodiment 3]
In the second embodiment, the extreme value classification unit 51 of FIG. 6 uses the minimum point or the maximum point of the low-frequency waveform 331 based on the main push-pull signal MPP to determine the minimum point of the differential push-pull signal DPP. It was classified. In the third embodiment, the extreme value classification unit 51 uses both the minimum point and the maximum point of the low-frequency waveform 331 based on the main push-pull signal MPP, and uses the minimum point of the low-frequency waveform 323 of the differential push-pull signal DPP. Classify.

  Specifically, in the case of the third embodiment, in step S506 in FIG. 7, the extreme value calculation unit 40 in FIG. 6 has both a minimum point and a maximum point with respect to the low-frequency waveform 331 based on the main push-pull signal MPP. Is calculated. A specific method for calculating a minimum point is the same as that described with reference to FIGS. 17 to 21, and a method for calculating a maximum point is the same as that described with reference to FIGS. 25 and 26, and thus detailed description will not be repeated.

  Next, the determination process in step S507 of FIG. 7 in the case of Embodiment 3 will be described.

  FIG. 30 is a diagram for explaining a method of classifying a plurality of minimum points of the low-frequency waveform 323 according to the third embodiment. In FIG. 30, a low frequency waveform 323 that is the difference between the upper and lower envelopes of the time series data of the differential push-pull signal DPP and a low frequency waveform 331 that is the average of the upper and lower envelopes of the time series data of the main push-pull signal MPP. Is shown. Here, the low frequency waveforms 323 and 331 are displayed with respect to a common time axis (X axis). Further, as shown in FIG. 30, in step S506 of FIG. 7, local minimum points Va1 to Va5 are extracted from the low frequency waveform 323, and local maximum points Rb1 to Rb3 and local minimum points Vb1 and Vb2 are extracted from the low frequency waveform 331. Has been extracted.

  In the case of the third embodiment, in step S651 of FIG. 22, the extreme value classification unit 51 of FIG. 6 performs the local minimum point Va2 of the low frequency waveform 323 obtained at substantially the same time as the local minimum points Vb1 and Vb2 of the low frequency waveform 331. , Va4 are classified into the first group, and the minimum points Va1, Va3, Va5 of the low frequency waveform 323 obtained at substantially the same time as the maximum points Rb1 to Rb3 of the low frequency waveform 331 are classified into the second group.

  As a result, according to the third embodiment, the false minimum points obtained when the adjustment of the diffraction grating is extremely insufficient or when the influence of the disturbance is exerted are the first and second groups. Not classified. Therefore, the optical pickup inspection apparatus 11 according to the third embodiment can determine the quality of the arrangement of the diffraction grating 104 in FIG. 1 with higher accuracy than in the second embodiment. Since other points of the third embodiment are the same as those of the second embodiment, description thereof will not be repeated.

[Embodiment 4]
The optical pickup inspection apparatus 11 according to the fourth embodiment is different from the first embodiment in the operation of the minimum point extraction unit 43 shown in FIG. Specifically, in the case of the first embodiment, in step S553 in FIG. 17, the local minimum point extraction unit 43 extracts the minimum point of each negative interval [Si, Ti] as the position of the local minimum point of the sampling waveform 324. (See description regarding FIG. 20). On the other hand, in Embodiment 4, the local minimum point extraction unit 43 extracts the barycentric position of the sampling waveform 324 in each negative section [Si, Ti]. Then, in step S554 in FIG. 17, the minimum point extraction unit 43 outputs a point on the low frequency waveform 323 corresponding to the extracted barycentric position as a minimum point of the low frequency waveform 323.

  FIG. 31 is a diagram for explaining the processing procedure of step S553 of FIG. FIG. 31A is a diagram illustrating the case of the first embodiment as a comparative example, and FIG. 31B is an explanatory diagram of the case of the fourth embodiment. 31A and 31B, it is assumed that negative intervals [S1, T1] to [S7, T7] in which the sampling waveform is lower than the smoothed waveform have already been extracted.

  As shown in FIG. 31A, in the case of the first embodiment, the minimum points V1 to V7 in the negative intervals [S1, T1] to [S7, T7] are extracted as the minimum points of the sampling waveform. At this time, when the minimum point V3 of the negative interval [S3, T3] is extracted as the minimum point when a plurality of minimum points are included as in the negative interval [S3, T3], the position of the minimum point is determined in the X-axis direction. It will be evaluated as a position deviated.

  Therefore, by calculating the barycentric position for the negative interval [S3, T3] and outputting the point V3_new on the sampling waveform corresponding to the barycentric position as a minimum point, the shift in the X-axis direction can be reduced. . As a result, it is possible to improve the quality accuracy of the final optical pickup device. A specific method for calculating the position of the center of gravity is as follows.

  In FIG. 31 (B), a straight line SiTi passing through points on both ends of the negative section [Si, Ti] is assumed. The coordinates of the data point Wi on the sampling waveform starting from the point Si and reaching the point Ti are (Xw, Yw), the coordinates of the point Si are (Xs, Ys), and the coordinates of the point Ti are (Xt, Yt). ). Further, the coordinates of the intersection of a straight line passing through each data point Wi and parallel to the Y axis and the straight line SiTi are (Xc, Yc).

  At this time, | Xw−Xs | × | Yw−Yc | is calculated for each data point Wi, and a sum Sum1 thereof is obtained. Further, | Yw−Yc | is calculated for each data point Wi, and a sum Sum2 thereof is obtained. At this time, the X coordinate of the center of gravity is given by Xs + Sum1 / Sum2.

  Since other points of the fourth embodiment are the same as those of the first embodiment, description thereof will not be repeated. Depending on how the low-frequency waveform is defined, for example, when the sign of the low-frequency waveform is inverted from the above case, it is necessary to calculate the barycentric position in each positive section of the sampling waveform 324. In this case, the local maximum point extraction unit 43 sets a point on the low-frequency waveform corresponding to the barycentric position of each positive section as the local maximum point.

[Embodiment 5]
FIG. 32 is a block diagram showing a schematic configuration of an optical pickup automatic adjustment device 12 according to Embodiment 5 of the present invention.

  Referring to FIG. 32, optical pickup 101A differs from optical pickup 101 in FIG. 1 in that it further includes an adjustment mechanism 113 that supports diffraction grating 104 and can adjust the position and orientation of diffraction grating 104. The adjustment mechanism 113 adjusts the position of the diffraction grating 104 in the x-axis, y-axis, and z-axis directions and the angle around each axis according to a command from the computer 201A. Since other points of optical pickup 101A are the same as those of optical pickup 101 in FIG. 1, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  The automatic adjustment device 12 of FIG. 32 includes an error signal generation unit 221, a computer 201A, and a display device 207 that displays an adjustment result. Since configurations of error signal generation unit 221 and display device 207 are the same as those in the first embodiment, description thereof will not be repeated.

  FIG. 33 is a block diagram showing a software configuration of a computer 201A that constitutes the automatic adjustment apparatus 12 of FIG. The computer 201A is different from the software configuration of the computer 201 in FIG. 6 in that the computer 201A further includes a diffraction grating adjustment unit 24 that controls the adjustment mechanism 113 of the diffraction grating 104. The diffraction grating adjustment unit 24 adjusts the arrangement of the diffraction grating 104 with respect to the laser light source 102 according to the comparison result by the comparison unit 52 configuring the determination unit 50. Since the other software configuration of computer 201A is the same as that of computer 201 in FIG. 6, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  FIG. 34 is a flowchart showing an adjustment procedure by the automatic adjustment device 12 of the optical pickup. The flowchart in FIG. 34 differs from the flowchart in FIG. 7 in that steps S508 and S509 are further included after step S507 in FIG.

  Referring to FIG. 34, the determination processing step in step S507 is the same as that in the first embodiment. Specifically, the extreme value classification unit 51 in FIG. 33 classifies the plurality of local minimum points calculated by the extreme value calculation unit 40 into first and second groups. The extreme value classification unit 51 classifies the plurality of minimum points V1 to V5 alternately into the first and second groups in time series order. Then, the comparison unit 52 in FIG. 33 calculates the average value of the minimum point values (minimum values) for each of the first and second groups.

  Next, in step S508 in FIG. 34, the comparison unit 52 in FIG. 33 obtains the difference between the ratio of the average value for each group and 1, and the pass / fail judgment threshold Th that the absolute value of the obtained difference is input in step S501. If (Th = 0.05) or less, it is determined that the arrangement of the diffraction grating is good (YES in step S508), and the adjustment procedure by the optical pickup automatic adjustment device 12 is completed.

  On the other hand, the comparison unit 52 in FIG. 33 determines that the arrangement of the diffraction grating is defective when the absolute value of the difference between the ratio of the average value for each group and 1 exceeds the pass / fail judgment threshold Th (Step S508). NO), the process proceeds to step S509.

  In step S509, the diffraction grating adjustment unit 24 of FIG. 33 causes the adjustment mechanism 113 to change the position and orientation of the diffraction grating 104 according to the determination result of the comparison unit 52. Specifically, it is as follows.

  First, the diffraction grating adjustment unit 24 determines whether the x-axis, y-axis, and z-axis directions and angles around each axis are good or bad in the state before adjustment (the ratio of the average value of extreme values for each group). ) Is stored in the storage device 203. Next, the diffraction grating adjustment unit 24 changes the position or orientation of the diffraction grating 104 in the positive direction or clockwise direction of each axis. Then, the diffraction grating adjustment unit 24 receives the pass / fail judgment result (value of the average value of the extreme values) in the adjusted state from the comparison unit 52, and approaches the target value of 1 as compared with the state before the adjustment. It is determined whether or not. When the target value is approaching 1, adjustment is continued in the same direction until the deviation between the pass / fail determination result and the target value is within the pass / fail determination threshold Th. When the deviation from 1 which is the target value becomes large, the adjustment direction of each axis is changed to the reverse direction.

  Steps S502 to S509 in FIG. 34 are repeated until it is determined in step S508 that the deviation between the pass / fail determination result and the target value is within the pass / fail determination threshold Th (YES in step S508). Since the other steps in FIG. 34 are the same as those in the first embodiment, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  According to the optical pickup automatic adjusting device 12 of FIG. 34, the optical pickup can be adjusted with high accuracy by evaluating the variation in the minimum value of the low-frequency waveform extracted from the time series data of the differential push-pull signal DPP. Can do. As a result, variations in the adjustment results of the optical pickup can be suppressed, adjustment time can be shortened, and labor costs can be reduced.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 11 Optical pick-up inspection apparatus, 12 Optical pick-up automatic adjustment apparatus, 21 Motor drive part, 22 Objective lens drive part, 23 Memory | storage part, 24 Diffraction grating adjustment part, 30 Waveform extraction part, 31 End point setting part, 32 Envelope generation Unit, 33 waveform calculation unit, 40 extreme value calculation unit, 41 sampling waveform generation unit, 42 smoothing unit, 43 minimum point (maximum point) extraction unit, 50 determination unit, 51 extreme value classification unit, 52 comparison unit, 101, 101A Optical pickup, 102 Laser light source (semiconductor laser), 104 Diffraction grating, 106 Optical recording medium, 107 Objective lens, 111 Actuator, 112 Spindle motor, 121 Main beam, 122, 123 Sub beam, 131 Four-segment photodetector, 132, 133 Two-part photodetector, 201, 201A Computer, 202 D conversion unit, 221 Error signal generation unit, 320, 328 Time series data, 321, 329 Upper envelope, 322, 330 Lower envelope, 323, 331 Low frequency waveform, 324, 326 Sampling waveform, 325, 327 Smoothing waveform , [Pi, Qi] positive interval, [Si, Ti] negative interval, DPP differential push-pull signal, MPP main push-pull signal, SPP, SPP1, SPP2 sub-push-pull signal.

Claims (17)

A laser light source;
A light branching element that branches light emitted from the laser light source into a plurality of light beams including a main beam and at least two sub beams;
An objective lens that focuses each of the plurality of light beams on an optical recording medium;
An actuator for repeatedly displacing the objective lens in a direction crossing a track of the optical recording medium;
An inspection apparatus for an optical pickup for inspecting an optical pickup including a plurality of photodetectors that respectively detect a plurality of reflected lights generated by reflecting each of the plurality of light beams on the optical recording medium,
An error signal generation unit that generates a differential push-pull signal based on outputs of the plurality of photodetectors as a tracking error signal;
An AD converter for digitally converting the differential push-pull signal obtained while the objective lens is repeatedly displaced;
A storage unit for storing first time-series data obtained by digitally converting the differential push-pull signal;
A waveform extraction unit that extracts a first waveform based on the first time-series data stored in the storage unit;
The first waveform is a waveform based on one of the upper and lower envelopes of the first time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes,
An extreme value calculation unit for calculating a plurality of maximum values or minimum values of the first waveform;
The quality of the arrangement of the optical branching element with respect to the laser light source is determined based on whether or not the variation of a plurality of maximum values or minimum values of the first waveform calculated by the extreme value calculation unit is within a predetermined range. An inspection apparatus for an optical pickup, further comprising a determination unit that performs the inspection. The waveform extraction unit
For each of the upper and lower envelopes of the first time series data, an endpoint setting unit that sets at least one of the left and right endpoints;
Starting from one of the left and right end points, each of the upper and lower envelopes is generated by sequentially extracting data points that satisfy a predetermined condition from the first time-series data in the positive or negative direction of the time axis. An envelope generator,
The optical pickup inspection apparatus according to claim 1, wherein the predetermined condition is that a slope of a straight line passing through adjacent data points falls within a predetermined range.   The envelope generation unit averages a plurality of first data points extracted in the positive direction of the time axis from the first time series data and a plurality of second data points extracted in the negative direction of the time axis. The optical pickup inspection device according to claim 2, wherein each of the upper and lower envelopes is generated by converting into an upper and lower envelope.   The envelope generation unit removes, from the first time-series data, data points that exceed a predetermined threshold and deviate from the upper and lower envelopes among the data points of the first time-series data. The optical pickup inspection device according to claim 2, wherein each of the upper and lower envelopes is generated again using the first time-series data from which noise has been removed.   When the end point setting unit sets each of the left and right end points, when the predetermined number of data points are arranged in order of size from the beginning or end of the first time-series data, the predetermined point data The optical pickup inspection apparatus according to claim 2, wherein a point value is set to an end point value. When the extreme value calculation unit calculates a plurality of minimum values of the first waveform,
A sampling waveform generation unit that divides the first waveform into a plurality of sections and generates a sampling waveform including the minimum points of the plurality of sections;
A smoothing unit that generates a smoothed waveform obtained by moving and averaging the sampling waveform;
A plurality of negative intervals in which a value obtained by subtracting the smoothed waveform from the sampling waveform is negative are extracted, and a minimum point of the sampling waveform in each of the plurality of negative intervals is extracted as a minimum point of the first waveform. The optical pickup inspection device according to claim 1, further comprising a minimum point extraction unit. When the extreme value calculation unit calculates a plurality of maximum values of the first waveform,
A sampling waveform generating unit that divides the first waveform into a plurality of sections and generates a sampling waveform composed of the maximum points of the plurality of sections;
A smoothing unit that generates a smoothed waveform obtained by moving and averaging the sampling waveform;
A plurality of positive intervals in which a value obtained by subtracting the smoothed waveform from the sampling waveform is positive are extracted, and a maximum point of the sampling waveform in each of the plurality of positive intervals is extracted as a maximum point of the first waveform. The optical pickup inspection apparatus according to claim 1, further comprising a local maximum point extraction unit. When the extreme value calculation unit calculates a plurality of minimum values of the first waveform,
A sampling waveform generation unit that divides the first waveform into a plurality of sections and generates a sampling waveform including the minimum points of the plurality of sections;
A smoothing unit that generates a smoothed waveform obtained by moving and averaging the sampling waveform;
A plurality of negative intervals in which the value obtained by subtracting the smoothed waveform from the sampling waveform is negative are extracted, and points on the first waveform corresponding to the centroid position of the sampling waveform in each of the plurality of negative intervals are determined. An inspection apparatus for an optical pickup according to claim 1, further comprising: a minimum point extraction unit that extracts a minimum point of the first waveform. When the extreme value calculation unit calculates a plurality of maximum values of the first waveform,
A sampling waveform generating unit that divides the first waveform into a plurality of sections and generates a sampling waveform composed of the maximum points of the plurality of sections;
A smoothing unit that generates a smoothed waveform obtained by moving and averaging the sampling waveform;
A plurality of positive intervals in which a value obtained by subtracting the smoothed waveform from the sampling waveform is positive are extracted, and points on the first waveform corresponding to the centroid position of the sampling waveform in each of the plurality of positive intervals are determined. The inspection apparatus for an optical pickup according to claim 1, further comprising: a maximum point extraction unit that extracts the maximum point of the first waveform. The determination unit
An extreme value classification unit that classifies a plurality of local maximum values or local minimum values calculated by the extreme value calculation unit into first and second groups;
By comparing an average value of a plurality of local maximum values or local minimum values belonging to the first group and an average value of a plurality of local maximum values or local minimum values belonging to the second group, the optical branching element for the laser light source The optical pickup inspection apparatus according to claim 1, further comprising a comparison unit that determines whether the arrangement of the optical pickup is good or bad.   The extreme value classification unit classifies a plurality of local maximum values or local minimum values calculated by the extreme value calculation unit into first and second groups alternately in the time order of the first time-series data. 10. The optical pickup inspection apparatus according to 10. The error signal generation unit further generates a main push-pull signal based on an output of a photodetector that detects reflected light of the main beam among the plurality of photodetectors,
The AD converter further digitally converts the main push-pull signal obtained while the objective lens is repeatedly displaced,
The storage unit further stores second time-series data obtained by digitally converting the main push-pull signal,
The waveform extraction unit further extracts a second waveform based on the second time series data stored in the storage unit,
The second waveform is a waveform based on one of the upper and lower envelopes of the second time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes,
The extreme value calculation unit further calculates a plurality of maximum values or minimum values of the second waveform,
The extreme value classification unit includes a maximum value of the second waveform calculated by the extreme value calculation unit or a plurality of maximum values or minimum values of the first waveform calculated by the extreme value calculation unit. The local maximum value or local minimum value obtained at approximately the same time as the time at which the local minimum value is given is classified into the first group, and the remaining local maximum value or local minimum value is classified into the second group. Optical pickup inspection device. The error signal generation unit further generates a main push-pull signal based on an output of a photodetector that detects reflected light of the main beam among the plurality of photodetectors,
The AD converter further digitally converts the main push-pull signal obtained while the objective lens is repeatedly displaced,
The storage unit further stores second time-series data obtained by digitally converting the main push-pull signal,
The waveform extraction unit further extracts a second waveform based on the second time series data stored in the storage unit,
The second waveform is a waveform based on one of the upper and lower envelopes of the second time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes,
The extreme value calculation unit further calculates a plurality of maximum values and minimum values of the second waveform,
The extreme value classifying unit is obtained at approximately the same time as the time when the minimum value of the second waveform is given among the plurality of local maximum values or local minimum values of the first waveform calculated by the extreme value calculating unit. Classifying the local maximum value or local minimum value into the first group, and classifying the local maximum value or local minimum value obtained at approximately the same time as the time of giving the local maximum value of the second waveform into the second group; The optical pickup inspection apparatus according to claim 10. A laser light source;
A light branching element that branches light emitted from the laser light source into a plurality of light beams including a main beam and at least two sub beams;
An objective lens that focuses each of the plurality of light beams on an optical recording medium;
An actuator for repeatedly displacing the objective lens in a direction crossing a track of the optical recording medium;
An inspection method of an optical pickup for inspecting an optical pickup including a plurality of photodetectors that respectively detect a plurality of reflected lights generated by reflecting each of the plurality of light beams by the optical recording medium,
Generating a differential push-pull signal based on the outputs of the plurality of photodetectors as a tracking error signal;
Digitally converting the differential push-pull signal obtained while the objective lens is repeatedly displaced;
Storing first time-series data obtained by digitally converting the differential push-pull signal;
Extracting a first waveform based on the first time-series data stored in the storing step,
The first waveform is a waveform based on one of the upper and lower envelopes of the first time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes,
Calculating a plurality of local maxima or minima of the first waveform;
The quality of the arrangement of the optical branching element with respect to the laser light source is determined based on whether or not the variation of the plurality of local maximum values or local minimum values of the first waveform calculated in the calculating step is within a predetermined range. And a step of inspecting the optical pickup. A laser light source;
A light branching element that branches light emitted from the laser light source into a plurality of light beams including a main beam and at least two sub beams;
An objective lens that focuses each of the plurality of light beams on an optical recording medium;
An actuator for repeatedly displacing the objective lens in a direction crossing a track of the optical recording medium;
A computer for inspecting an optical pickup including a plurality of photodetectors that respectively detect a plurality of reflected lights generated by reflection of each of the plurality of light beams by the optical recording medium;
Storing the differential push-pull signal generated and digitally converted based on the outputs of the plurality of photodetectors as first time-series data while the objective lens is repeatedly displaced;
Performing a step of extracting a first waveform based on the first time-series data stored in the storing step;
The first waveform is a waveform based on one of the upper and lower envelopes of the first time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes,
Calculating a plurality of local maxima or minima of the first waveform;
The quality of the arrangement of the optical branching element with respect to the laser light source is determined based on whether or not the variation of the plurality of local maximum values or local minimum values of the first waveform calculated in the calculating step is within a predetermined range. And an inspection program for further executing the step.   A computer-readable recording medium on which the inspection program according to claim 15 is recorded. A laser light source;
A light branching element that branches light emitted from the laser light source into a plurality of light beams including a main beam and at least two sub beams;
An objective lens that focuses each of the plurality of light beams on an optical recording medium;
An actuator for repeatedly displacing the objective lens in a direction crossing a track of the optical recording medium;
An optical pickup automatic adjustment device for automatically adjusting an optical pickup including a plurality of photodetectors that respectively detect a plurality of reflected lights generated by reflecting each of the plurality of light beams on the optical recording medium. And
An error signal generation unit that generates a differential push-pull signal based on outputs of the plurality of photodetectors as a tracking error signal;
An AD converter for digitally converting the differential push-pull signal obtained while the objective lens is repeatedly displaced;
A storage unit for storing first time-series data obtained by digitally converting the differential push-pull signal;
A waveform extraction unit that extracts a first waveform based on the first time-series data stored in the storage unit;
The first waveform is a waveform based on one of the upper and lower envelopes of the first time-series data, the sum of the upper and lower envelopes, or the difference between the upper and lower envelopes,
An extreme value calculation unit for calculating a plurality of maximum values or minimum values of the first waveform;
The quality of the arrangement of the optical branching element with respect to the laser light source is determined based on whether or not the variation of a plurality of maximum values or minimum values of the first waveform calculated by the extreme value calculation unit is within a predetermined range. A determination unit to perform,
An automatic adjustment device for an optical pickup, further comprising: an adjustment unit that adjusts an arrangement of the optical branching element with respect to the laser light source in accordance with a determination result of the determination unit.

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