JP2011096299A - Optical information processing method and optical information recording device equipped with optical information processing function thereof - Google Patents

Abstract

A focus offset process and a spherical aberration process of an optical pickup are realized in a short time and accurately.
The method of the present invention includes a servo control step S2 for executing focus servo and tracking servo, and detecting spherical aberration as a position of a collimating lens, and the amount of displacement of the collimating lens and the amount of offset of the objective lens are in a ratio K. The collimating lens and the objective lens are changed in parallel so that the best point M3 of the collimating lens and the objective lens where the value of the signal quality index representing the quality of the optical information signal is the best is searched. The search step S3 and the position of the collimator lens and the objective lens are changed in parallel so that the displacement amount of the collimator lens and the offset amount of the objective lens are in a ratio of −1 / K with the best point M3 as a base point. Search for the best point M6 of the collimating lens and the objective lens with the best quality index value And a second search step S4.
[Selection] Figure 4

Description

  The present invention relates to an optical information processing method and an optical information recording apparatus. More specifically, the present invention relates to an optical information processing method for performing spherical aberration correction processing and focus offset adjustment processing on an optical pickup, and an optical information recording apparatus having the optical information processing function.

  In recent years, an optical disk is a recording medium capable of recording a large amount of information signals at a high density, and therefore has been used in many fields such as audio, video, and computers. An optical disk is a generic term for recording media that read disk information by irradiating a disk with a thin metal plate protected by a transparent protective substrate (cover layer) with laser light and detecting the return light. Examples of the optical disk include a DVD and a CD. In recent years, a high-density optical disk called a BD (Blue-ray Disc) has been put into practical use.

  In order to read information on a high-density optical disc, it is necessary to reduce the beam spot of the laser light emitting element. In order to reduce the spot, it is necessary to increase the numerical aperture of the optical system and use light having a shorter wavelength. Therefore, when reading information from a high-density optical disk, the problem of spherical aberration due to the thickness error of the cover layer increases. In order to cope with this problem, it is necessary to perform spherical aberration correction. For example, Patent Document 1 discloses an optical pickup including a beam expander as a lens group for correcting spherical aberration.

  As a method for adjusting the spherical aberration correction amount and the focus offset amount, the following methods are well known. That is, a method is known in which a point at which the reproduction signal quality is the best is searched step by step while the spherical aberration correction unit and the focus offset adjustment unit are alternately changed one by one.

  For example, in the method disclosed in Patent Document 2, while the tracking control is in the OFF state, the spherical correction unit and the focus offset adjustment unit are operated alternately, and a plurality of tracking error signal amplitudes larger than a predetermined value are obtained. A first search for searching for a set of spherical aberration amount and focus offset adjustment position is executed. Then, after the first search, while the tracking control is in the ON state, a set of a plurality of sets obtained in the first search from which the reproduction signal quality is substantially best among the adjustment positions. A second search for determining the spherical aberration amount and the focus offset adjustment position is executed.

  Further, in the method disclosed in Patent Document 3, when the focus offset amount is defined as X and the spherical aberration amount is defined as Y, the focus is on the straight line “Y = aX + Y0” having a slope a passing through the predetermined spherical aberration Y0. The focus offset position X1 and the spherical aberration amount Y1 at which the jitter value is minimized are searched by changing the offset position X and the spherical aberration amount Y. Then, the focus position X and the spherical aberration amount Y are set on a straight line “Y = − (X−X1) / a + Y1” having a slope −1 / a passing through the minimum jitter search position (X1, Y1). The focus position and the spherical aberration amount at which the jitter value is minimized by searching are searched.

JP 2002-352449 A (released on December 6, 2002) Japanese Patent Laying-Open No. 2005-196947 (published July 21, 2005) JP 2007-188632 A (published July 26, 2007)

  However, the above-described conventional technology has the following problems.

  First, in a method in which the spherical signal correcting means and the focus offset adjusting means are alternately changed one by one and searching for the point where the reproduction signal quality is the best, either the spherical correction means or the focus offset adjusting means is used. When moved, the amplitude of the tracking error signal becomes small and the tracking control becomes unstable. As a result, a problem that servo control becomes unstable during adjustment may occur. In addition, since the spherical surface correcting means and the focus offset adjusting means are operated alternately and repeatedly in a stepwise manner, the adjustment takes time.

  On the other hand, in the method disclosed in Patent Document 2, after searching for the amplitude of the tracking error signal when the tracking control is off, the reproduction signal quality is further searched when the tracking control is on. Therefore, the adjustment can be performed in a state where the tracking control is stable. However, on the other hand, while the tracking control is in the off state, the spherical correction means and the focus offset adjustment means are operated alternately, and it takes a considerable time to search for the edge of the tracking error signal amplitude. Further, after that, it is necessary to search for the best point of the reproduction signal quality at least once with the tracking control turned on. In addition, if there is no playback signal quality best point on the edge of the tracking error signal amplitude, an additional step of searching for the best playback signal quality is required, so to find the best playback quality best point However, there is a problem that the search needs to be repeated and the adjustment time becomes very long.

  With the method disclosed in Patent Document 3, the number of measurement points can be reduced, and a high-speed search is possible. However, for the search, it is necessary to detect a spherical aberration signal as the amount of spherical aberration. Therefore, in order to detect the spherical aberration signal with high accuracy, complicated arithmetic processing is required, and a large-scale signal detection circuit is required. Further, since the spherical aberration signal is greatly affected by temperature, it is considered that tracking servo control becomes unstable due to temperature change. In addition, the definition of the search start position is unclear, and depending on the setting method, the jitter at the search start position may be poor, tracking servo control may become unstable, or tracking servo control may not be started. .

  The present invention has been made in view of the above-described problems, and an object thereof is an optical information processing method capable of performing focus offset processing and spherical aberration processing of an optical pickup in a short time and accurately, Another object is to provide an optical information recording apparatus having the optical information processing function.

  In order to solve the above problems, an optical information processing method of the present invention condenses a light beam emitted from a light source on an optical recording medium by a condensing member, and converts the light beam reflected from the optical recording medium into a light beam. For an optical pickup to be detected as an information signal, spherical aberration correction processing for correcting spherical aberration generated in the light beam irradiated on the optical recording medium, and for the condensing member, the light beam is combined on the signal recording surface of the optical recording medium. In an optical information processing method for performing a focus offset adjustment process for adjusting an offset amount in an optical axis direction so as to be in focus, a servo control step for performing focus servo control and tracking servo control based on the optical information signal, and spherical aberration Is detected as the position of the correction optical member for correcting the spherical aberration, and the offset of the condensing member with respect to the displacement amount of the correction optical member is detected. The position of the correction optical member and the condensing member are changed in parallel so that the ratio of the amount of light is a predetermined ratio K, and the value of the signal quality index representing the quality of the optical information signal is the best. A first search step for searching for a first best position of the correction optical member and the light collecting member, and an offset amount of the light collecting member with respect to a displacement amount of the correction optical member with the first best position as a base point The position of the correction optical member and the light condensing member are changed in parallel so that the ratio becomes a predetermined ratio-1 / K, and the value of the signal quality index is the best, and the correction optical member and the light collection member. And a second search step for searching for the second best position of the optical member.

  The optical information processing method of the present invention relates to an optical pickup that condenses a light beam emitted from a light source onto an optical recording medium by a condensing member, and detects the light beam reflected from the optical recording medium as an optical information signal. Spherical aberration correction processing for correcting spherical aberration generated in the light beam irradiated on the optical recording medium, and offset in the optical axis direction so that the light beam is focused on the signal recording surface of the optical recording medium with respect to the condensing member This is a method of performing a focus offset adjustment process for adjusting the amount.

  Then, focus servo control and tracking servo control are executed based on the optical information signal in the servo control step to detect a signal quality index representing the quality of the optical information signal, and the detected signal quality index value is the best. The spherical aberration correction amount and the focus offset amount are determined.

  According to the above configuration, in both the first search step and the second search step, the position of the correction optical member for correcting spherical aberration and the position of the light collecting member are changed in parallel, and the value of the signal quality index is set. Is searching for the best position. Therefore, according to the above configuration, the servo control is less than that in the conventional method in which the spherical aberration correcting unit and the focus offset adjusting unit are operated alternately to search for the position where the reproduction signal quality is the best. It becomes possible to perform processing in a short time without becoming stable.

  Furthermore, according to the above configuration, since the spherical aberration is detected as the position of the correction optical member for correcting the spherical aberration in the first search step and the second search step, the reflected light from the optical recording medium is detected. Compared with the method of detecting the amount of spherical aberration from the spherical aberration signal obtained by detecting and calculating the spherical aberration signal, the detection circuit can be simplified, and the influence of the environment such as temperature is relatively small, so it is adjusted accurately. It is possible.

  As described above, according to the above configuration, it is possible to realize an optical information processing method capable of performing the focus offset process and the spherical aberration process of the optical pickup in a short time and accurately.

  For the ratio K, the first contour map indicating the characteristics of the signal quality index with respect to the position of the correction optical member and the position of the light condensing member, and the position of the correction optical member and the position of the light condensing member It can be determined based on the second contour map indicating the characteristics of the amplitude of the tracking error signal.

  That is, among the arbitrary straight lines extending along the ridgeline of the first contour map, the slope of the straight line most parallel to the ridgeline of the second contour map can be set as the ratio K.

  By determining the ratio K in this way, when performing the spherical aberration correction process and the focus offset adjustment process of the optical pickup, in the first search step, the correction optical signal is corrected at a ratio with a small change in the amplitude distribution of the tracking error signal. The positions of the member and the light collecting member are changed in parallel. Accordingly, spherical aberration correction processing and focus offset adjustment processing can be performed without causing tracking control to become unstable, such as tracking servo loss due to a decrease in the amplitude of the tracking error signal. Further, since the number of positions for measuring the signal quality index can be reduced, the adjustment time can be shortened.

  In the optical information processing method of the present invention, in the first search step, the parallel light position when the light beam passing through the correction optical member becomes parallel light in the optical system including the light source and the correction optical member is determined. The optical pickup picks up the calculated position so that the spherical aberration is minimized when the correction optical member is moved from the parallel light position and focused on the signal recording surface of the optical recording medium. The starting position is preferred.

  When the search start position of the first search is uniformly set for all the optical pickups, tracking servo control is performed at the start of the first search step due to assembly variations of the optical system of each optical pickup. May not be stable, or tracking servo control may not be possible.

  According to the above configuration, in the first search step, the parallel light position when the light beam passing through the correction optical member becomes parallel light in the optical system including the light source and the correction optical member is stored. In the optical pickup, the position where the correction optical member is moved from the parallel light position and the focal point is calculated on the signal recording surface of the optical recording medium so that the spherical aberration is minimized is the search start position. Therefore, it is possible to eliminate variations due to assembly errors of the correction optical member and other optical systems. For this reason, a more stable search is possible as compared with the method of setting the search start position to a certain fixed value.

  According to the optical information processing method of the present invention, in the first search step and the second search step, the signal quality index is a combination of at least three positions of the correction optical member and the position of the light collecting member. The first search step and the second search step are approximated from the measurement results of the combinations of the positions, respectively, by approximating the signal quality index with respect to the position of the correction optical member and the position of the light collecting member. A first approximate curve creating step for creating a curve, and a first calculation step for calculating the position of the correction optical member and the light collecting member, from which the value of the signal quality index is the best, from the approximate curve. It is preferable to include.

  According to the above configuration, in the first search step and the second search step, the value of the signal quality index is a combination of at least three positions of the correction optical member and the position of the light collecting member. In the first approximate curve creation step, an approximate curve of the signal quality index for the position of the correction optical member and the position of the light collecting member is created from the measurement result of each position combination, and the first calculation is performed. In the step, the position of the correction optical member and the light condensing member with which the value of the signal quality index is the best is calculated from the approximate curve. The number of position combinations can be reduced, and accurate adjustment can be performed. Note that the number of combinations of the positions to be searched may be at least three, but more accurate adjustment is possible by increasing the number of combinations of the positions.

  According to the optical information processing method of the present invention, in the first search step and the second search step, the signal quality index is a combination of at least three positions of the correction optical member and the position of the light collecting member. The first search step and the second search step are respectively a comparison step for comparing the signal quality index values measured at the respective combinations of positions, and a signal quality index based on the comparison result. From the measurement result of the signal quality index including the additional measurement step including at least one combination of the position of the correction optical member and the position of the light collecting member to be measured, and the additional measurement step, the correction optical A second approximate curve creating step for creating an approximate curve of a signal quality index for the position of the member and the position of the light collecting member, and the signal quality indicator from the approximate curve. It is preferable to include a second calculation step of calculating the position of the correction optical member and the light condensing member in which the standard value is the best.

  The assembled optical pickups have different tracking error signal amplitudes and reproduction signal quality distributions (characteristics) depending on the accuracy of optical components, assembly errors, and variations in the sensitivity of photodetectors that detect reflected light. Accordingly, when the signal quality index value is measured at the same position combination for all of the assembled optical pickups and the best position of the correction optical member and the light collecting member is searched, the distribution characteristic of the tracking error signal amplitude is shifted. In the optical pickup, the amplitude of the tracking error signal at the measurement position becomes small, which may cause a tracking control error. In addition, the change in the value of the signal quality index between the measurement positions becomes small, and there is a possibility that the best position cannot be calculated by the approximate curve.

  According to the above configuration, in the first search step and the second search step, the value of the signal quality index is a combination of at least three positions of the correction optical member and the position of the light collecting member. And comparing the signal quality index values measured at each position combination in the comparison step. In the additional measurement step, based on the comparison result of the comparison step, at least one combination of the position of the correction optical member and the position of the light collecting member where the value of the signal quality index is to be measured is added. From the signal quality index measurement results including the additional measurement step in the approximate curve creation step, an approximate curve of the signal quality index for the position of the correction optical member and the position of the light collecting member is created. Add at least one combination of the position of the correcting optical member and the position of the condensing member for which the value of the signal quality index is to be measured in accordance with the deviation of the distribution of the signal quality index due to assembly errors and component tolerances. A curve can be created. Then, in the second calculation step, tracking servo control is performed by calculating the position of the correction optical member and the condensing member where the value of the signal quality index is the best from the approximate curve thus created. More accurate adjustment is possible without becoming unstable.

  In the optical information processing method of the present invention, the signal quality indicator is a jitter of the reproduction signal, and the correction optical member that minimizes the value of the jitter of the reproduction signal in the first search step and the second search step. It is preferable to search for the position of the light collecting member.

  According to the above configuration, jitter is highly correlated with the quality of the recorded information that must be ensured as an optical pickup, so the signal processing is relatively simple and higher compensation accuracy. Thus, spherical aberration correction processing and focus offset adjustment processing can be performed.

  In the optical information processing method of the invention, the signal quality index is the amplitude of the reproduction signal, and in the first search step and the second search step, the correction optical member that maximizes the value of the reproduction signal amplitude and It is preferable to search for the position of the light collecting member.

  According to the above configuration, since the reproduction signal of the recorded information whose quality must be ensured as an optical pickup is directly used as an index, accurate adjustment can be performed and complicated signal processing is not required. The circuit can perform spherical aberration correction processing and focus offset adjustment processing.

  In the optical information processing method of the invention, the signal quality index is an error rate of the reproduction signal, and the correction optical that minimizes the value of the error rate of the reproduction signal in the first search step and the second search step. It is preferable to search for the position of the member and the light collecting member.

  According to the above configuration, the error rate that is highly correlated with the quality of the recorded information that must ensure the quality as an optical pickup is used as the reference signal, so that compensation with the highest accuracy and sensitivity is performed. Can do.

  In order to solve the above-described problems, the optical information recording apparatus of the present invention condenses the light beam emitted from the light source onto the optical recording medium by the condensing member, and emits light from the light beam reflected from the optical recording medium. For an optical pickup that detects an information signal, a spherical aberration correction process that corrects a spherical aberration that occurs in the light beam that irradiates the optical recording medium, and for the condensing member, the light beam is combined on the signal recording surface of the optical recording medium In an optical information recording apparatus including an optical information processing unit that performs a focus offset adjustment process for adjusting an offset amount in an optical axis direction so as to be in focus, the optical information processing unit performs focus servo control based on the optical information signal. And a servo control unit that executes tracking servo control, and based on the optical information signal detected by the optical pickup, the quality of the optical information signal is adjusted. The signal quality indicator is detected, the spherical aberration is detected as the position of the correction optical member for correcting the spherical aberration, and the ratio of the offset amount of the condensing member to the displacement amount of the correction optical member becomes a predetermined ratio K. As described above, the positions of the correction optical member and the light condensing member are changed in parallel, and the first best position of the correction optical member and the light condensing member in which the value of the signal quality index is the best is searched. 1 is performed, and the correction is performed so that the ratio of the offset amount of the light collecting member to the displacement amount of the correction optical member is a predetermined ratio−1 / K with the first best position as a base point. A second search step of searching for a second best position of the correction optical member and the light collecting member, wherein the positions of the optical member and the light collecting member are changed in parallel, and the value of the signal quality index is the best. The fruit It is characterized in that.

  According to said structure, the optical information recording device which can perform the focus offset process and spherical aberration process of an optical pick-up accurately in a short time is realizable.

  As described above, the optical information processing method of the present invention includes a servo control step for executing focus servo control and tracking servo control based on the optical information signal, and a spherical optical aberration and a correction optical member for correcting the spherical aberration. The position of the correction optical member and the light collecting member is changed in parallel so that the ratio of the offset amount of the light collecting member to the displacement amount of the correction optical member is a predetermined ratio K. A first search step for searching for a first best position of the correction optical member and the condensing member in which a value of a signal quality index representing the quality of the optical information signal is the best, and a base point of the first best position The position of the correction optical member and the light condensing member so that the ratio of the offset amount of the light condensing member to the displacement amount of the correction optical member is a predetermined ratio-1 / K. Parallel by changing the value of the signal quality index is optimized, a configuration and a second searching step of searching for second best position of the correction optical member and the condensing member.

  As described above, in the optical information recording apparatus of the present invention, the optical information processing unit has a servo control unit that performs focus servo control and tracking servo control based on the optical information signal. The correction optical member and the light collection member are detected as the position of the correction optical member that corrects the spherical aberration, and the ratio of the offset amount of the light collection member to the displacement amount of the correction optical member becomes a predetermined ratio K. The first search step for searching for the first best position of the correction optical member and the condensing member where the value of the signal quality index is the best is performed, and the first search step is executed. Positions of the correction optical member and the condensing member so that a ratio of the offset amount of the condensing member to a displacement amount of the correction optical member is a predetermined ratio-1 / K with the best position as a base point Parallel by changing the value of the signal quality index is optimized, it is configured to perform a second search step of searching for second best position of the correction optical member and the condensing member.

  Therefore, the focus offset process and the spherical aberration process of the optical pickup can be realized in a short time and accurately.

1 is a block diagram showing a schematic configuration of an optical information recording apparatus according to Embodiment 1. FIG. It is a schematic diagram which shows the hologram pattern formed in the hologram element of the optical information recording device shown in FIG. The collimating lens is focused on the recording layer in a focused state so that spherical aberration does not occur in the focused beam from the objective lens with respect to the thickness of the cover layer of the optical disk. It is a schematic diagram which shows the light beam on the photodetector in the case of doing. (A) is a flowchart which shows the basic sequence of a spherical aberration correction process and a focus offset adjustment process, (b) is a flowchart which shows the procedure of the 1st search step of a spherical aberration correction process and a focus offset adjustment process. 10 is a flowchart showing a procedure of a second search step of spherical aberration correction processing and focus offset adjustment processing. It is a graph for demonstrating the measurement location of the reproduction | regeneration signal quality parameter | index of a 1st search step and a 2nd search step, (a) is RF signal amplitude (RF amplitude) with respect to a focus offset and the position of the collimating lens 22. FIG. ) Is a graph showing the simulation result of the characteristic of (), and (b) is a graph showing the simulation result of the characteristic of the tracking error signal amplitude (PP amplitude) with respect to the focus offset and the collimating lens position. 3 is a graph for explaining the experimental results by the inventor of the present application, in which (a) is a graph showing the contour characteristics of the RF signal jitter characteristics with respect to the focus offset and the collimating lens position in the optical information recording apparatus of FIG. (B) is a graph showing the contour map of the experimental results of the tracking error signal amplitude (PP amplitude) with respect to the focus offset and the collimating lens position in the optical information recording apparatus of FIG. FIG. 9 is a flowchart showing a procedure of a first search step and a second search step in spherical aberration correction processing and focus offset adjustment processing according to Embodiment 2, and (a) shows the procedure of the first search step. , (B) shows the procedure of the second search step. It is a graph for demonstrating the experimental result by this inventor, (a) is a graph which showed the characteristic of the jitter of RF signal with respect to a focus offset and a collimating lens position with the contour map, (b) is a focus It is the graph which showed the experimental result of the tracking error signal amplitude (PP amplitude) with respect to an offset and a collimating lens position by the contour map.

  The present invention relates to optical information for performing spherical aberration correction processing and focus offset adjustment processing for an optical pickup used in an optical information recording apparatus that records / reproduces information on a writable optical disk such as a write once type or a rewritable type at a high density. The present invention relates to a processing method and an optical information recording apparatus having the optical information function.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the present embodiment.

[Embodiment 1]
The following describes Embodiment 1 of the present invention with reference to FIGS.

  FIG. 1 is a block diagram showing a schematic configuration of an optical information recording apparatus 100 according to Embodiment 1 of the present invention. As shown in FIG. 1, the optical information recording apparatus 100 includes an optical information processing unit 1 and an optical pickup 2. The optical pickup 2 irradiates a read beam light toward an optical disk 4 as an optical recording medium that is rotationally driven by a spindle motor 3, and receives the reflected light as a light reception signal. Then, the light reception signal is converted into an electric signal and supplied to the optical information processing unit 1. The optical information processing unit 1 includes a focus error generation circuit 11, a tracking error generation circuit 12, and an RF signal generation circuit 13. Based on the input electric signal (light reception signal), a focus error signal, a tracking error signal, And a reproduction signal is generated.

  The pickup 2 includes a laser generating element (light source) 21, a collimating lens (correcting optical member) 22, a collimating lens actuator 23, a quarter wavelength plate 25, an objective lens (condensing member) 26, an objective lens actuator 27, and a hologram. An element 28, a polarization beam splitter 29, and a photodetector 30 are provided.

  The laser generating element 21 generates laser beam light (linearly polarized light) having a predetermined optical power and emits the laser beam toward the optical disc 4. The laser beam light emitted from the laser generating element 21 is converted into parallel light by the collimating lens 22.

  Here, the optical pickup 2 is provided with a collimating lens actuator 23 for moving the collimating lens 22 in the optical axis direction. The collimating lens actuator 23 moves the collimating lens 22 in the optical axis direction based on a driving signal from a collimating lens driving circuit 15 described later. Thereby, the spherical aberration due to the thickness error of the transmission substrate for each optical disk 4 is corrected.

  The amount of movement of the collimating lens 22 is detected by a position sensor 24 built in the collimating lens actuator 23. Examples of the combination of the collimating lens actuator 23 and the position sensor 24 include a configuration in which a stepping motor and a photo interrupter are combined, and a configuration in which a piezoelectric actuator and a Hall element are combined. When the stepping motor and the photo interrupter are combined, the photo interrupter detects only the initial position of the collimating lens 22. The amount of movement of the collimator lens 22 is managed by the number of pulses applied to the stepping motor. On the other hand, when the piezoelectric actuator and the hall element are combined, the absolute amount of the movement amount of the collimator lens 22 is detected by the hall element.

  The laser beam light that has passed through the collimating lens 22 is converted from linearly polarized light to circularly polarized light by the quarter wavelength plate 25. The objective lens 26 condenses the laser beam light on a recording track formed on the recording surface of the optical disc 4.

  The objective lens 26 is mounted on the objective lens actuator 27 and is driven in the optical axis direction (focus direction) of the optical system or in the disc radial direction of the optical disc 4. The objective lens 26 is driven in the optical axis direction based on a focus error signal generated by the focus error generation circuit 11. The objective lens 26 is driven in the disk radial direction based on a signal from the tracking error generation circuit 12. As the objective lens actuator 27, for example, a configuration using a voice coil motor as a drive source can be cited.

  Thus, the optical pickup 2 irradiates the recording track of the optical disc 4 with the laser beam emitted from the laser generating element 21 as the reading beam light. Reflected light (returned light) obtained by irradiating the recording track of the optical disk 4 passes through the objective lens 26, is converted from circularly polarized light to linearly polarized light by the λ / 4 plate 25, and enters the hologram element 28. At this time, the return light is diffracted by the hologram element 28, separated into 0th-order diffracted light (non-diffracted light) and ± 1st-order diffracted light (diffracted light), and enters the polarization beam splitter 52. The return light separated into the 0th-order diffracted light (non-diffracted light) and the ± 1st-order diffracted light (diffracted light) is reflected by the polarization beam splitter 29 and condensed on the light receiving surface of the photodetector 30 to be converted into an electric signal. Converted. A detailed hologram pattern in the hologram area of the hologram element 28 will be described later.

  The optical information processing unit 1 generates a focus error signal, a tracking error signal, and a reproduction signal based on the electrical signal converted by the photodetector 30.

  The focus error generation circuit 11 adds and subtracts a plurality of output signals detected by the photodetector 30 to generate a focus error signal. This focus error signal serves as an index of the amount of positional deviation between the convergence position of the laser beam irradiated onto the optical disc 4 and the information surface of the optical disc 4. Astigmatic method or knife edge method is used as a method for detecting the focus error signal.

  The tracking error generation circuit 12 adds and subtracts a plurality of output signals detected by the photodetector 30 to generate a tracking error signal. This tracking error signal is an indicator of the amount of positional deviation between the spot of the light beam formed on the information surface of the optical disc 4 and the track on the information surface of the optical disc 4. As a tracking error signal detection method, a push-pull method or a phase difference method is used.

  The RF signal generation circuit 13 generates an RF signal indicating reproduction information based on the output signal of the photodetector 30.

  In the optical information processing unit 1, the focus error signal generated by the focus error generation circuit 11 and the tracking error signal generated by the tracking error generation circuit 12 are input to a servo control circuit (servo control unit) 14. . On the other hand, the RF signal generated by the RF signal generation circuit 13 is input to the main control circuit 16.

  The servo control circuit 14 includes a phase compensation circuit, a servo pull-in logic circuit, and an objective lens actuator drive circuit (not shown). Based on the input focus error signal and tracking error signal, a drive signal is supplied to the objective lens actuator 27. Thereby, control of the focus servo and tracking servo is performed.

  The collimating lens driving circuit 15 supplies a driving signal to the collimating lens actuator 23 to drive the collimating lens 22. The driving signal is supplied to the collimating lens actuator 23 of the collimating lens driving circuit 15 by a command from the main control circuit 16.

  The main control circuit 16 sends commands to each circuit board and collects data output from each circuit board. Specifically, a command to correct spherical aberration is sent to the collimating lens driving circuit 15, a focus offset adjustment signal is sent to the servo control circuit 14, and RF signal data is collected from the RF signal generating circuit. Is the main role. For this reason, the main control circuit 16 includes a CPU having an arithmetic function, a ROM for recording predetermined programs and data, a working RAM, and a memory for writing adjustment results.

  Hereinafter, calculation for generating a focus error signal, a tracking error signal, and a reproduction signal in the present embodiment will be described with reference to FIGS. FIG. 2 is a schematic diagram showing a hologram pattern formed on the hologram element 28. As shown in FIG. 2, the hologram pattern of the hologram element 28 is composed of six regions 28a to 28f.

  Next, the relationship between the division pattern of the hologram element 28 and the light receiving portion pattern of the photodetector 30 will be described with reference to FIG. FIG. 3 shows a state in which the position of the collimator lens 22 in the optical axis direction is adjusted so that spherical aberration does not occur in the focused beam by the objective lens 26 with respect to the thickness of the cover layer of the optical disc 4. Fig. 5 shows a light beam on the photodetector 30 when the light is focused in a focused state. Actually, the center position of the hologram element 28 is set at a position corresponding to the center position of the light receiving portions 30 a to 30 d of the photodetector 30. In FIG. 3, for the sake of explanation, the hologram element 28 is shown shifted in the Y direction.

  The laser beam light condensed by the objective lens 26 in the forward optical system is reflected by the recording surface of the optical disk 4 and is reflected by the hologram element 28 in the backward optical system by the 0th-order diffracted light (non-diffracted light) and the + 1st-order diffracted light (diffracted light). And separated.

  The photodetector 30 includes a light receiving unit for receiving a light beam necessary for detection of a reproduction signal (RF signal) or a servo signal among 0th-order diffracted light and + 1st-order diffracted light, and 12 light beams 30a to 30l. It is comprised by the light-receiving part. 30a-30d are installed as a light-receiving part which receives 0th order diffracted light (non-diffracted light). In addition, 30i and 30j are installed as light receiving units that receive the + 1st order diffracted light diffracted in the region 28a. Further, 30k and 30l are installed as light receiving portions that receive the + 1st order diffracted light diffracted in the region 28b. 30e and 30h are provided as light receiving portions for receiving ± first-order diffracted light diffracted in the regions 28c and 28f, respectively. In addition, 30f and 30g are installed as light receiving portions that receive ± first-order diffracted light diffracted by the regions 28d and 28e, respectively.

  Next, operations for generating an RF signal, a tracking error signal, and a focus error signal will be described. Here, signals output from the light receiving units 30a to 30l are represented as Sa to Sl.

The RF signal (RF) is detected using non-diffracted light. That is, the RF signal (RF) is expressed by the following arithmetic expression:
RF = Sa + Sb + Sc + Sd
Given in.

  The tracking error signal is detected using a phase difference method (DPD method) or a phase shift DPP method.

  When the phase difference method (DPD method) is used, the tracking error signal (TES1) is detected by performing phase comparison of Sa to Sd.

When using the phase shift DPP method, the tracking error signal (TES2) is expressed by the following equation:
TES2 = {(Sa + Sb) − (Sc + Sd)} − α {(Sf + Sg) − (Se + Sh)}
Given in. Here, α is set to an optimum coefficient for canceling offset due to objective lens shift or optical disc tilt.

The focus error signal (FES) is detected using a double knife edge method. That is, FES is the following arithmetic expression:
FES = (Si-Sj)-(Sk-Sl)
Given in.

  As described above, the optical information processing unit 1 generates the RF signal by the RF signal generation circuit 13, and generates the focus error signal and the tracking error signal by the focus error generation circuit 11 and the tracking error generation circuit 12, respectively. Performs operation and tracking servo operation. The focus servo operation and tracking servo operation are performed to perform spherical aberration correction processing and focus offset adjustment processing.

  Next, spherical aberration correction processing and focus offset adjustment processing by the optical information processing unit 1 will be described with reference to FIGS. FIG. 4A is a flowchart showing a basic sequence of spherical aberration correction processing and focus offset adjustment processing in the present embodiment.

  First, in step S1, the spindle motor is operated to rotate the optical disc. Then, the laser generating element 21 is driven to irradiate the optical disk 4 with laser beam light (spindle motor ON, laser ON).

  Next, in step S2 (servo control step), in order to execute the focus servo operation, a command is issued from the control system 16 to the main control circuit 14, and the focus servo operation is started. Subsequently, in order to execute the tracking servo operation, a command is issued from the main control circuit 16 to the servo control circuit 14, and the tracking servo operation is started (focus servo ON, tracking servo ON).

  In step S3, a first search step, which is an initial search for searching for the best reproduction signal quality, is performed. The flow of the first search step will be described later.

  In step S4, a second search step which is a second search for searching for the best point of the reproduction signal quality is executed. The flow of the second search step will be described later.

  In step S5, adjustment is made to the optimum spherical aberration correction position and the optimum focus offset position calculated in the second search step, and the adjustment flow is completed.

  Next, the first search step (step S3) and the second search step (step S4) will be described in more detail. FIG. 4B is a flowchart showing the procedure of the first search step in the spherical aberration correction process and the focus offset adjustment process according to the present embodiment.

  As shown in FIG. 4B, first, in step S11, the three predetermined positions are changed while changing both the position of the collimating lens 22 and the focus offset at a predetermined ratio K from a predetermined search start position. A reproduction signal quality index (signal quality index) is measured for each combination. In other words, the reproduction signal quality index for each of the three points M0, M1, and M2 is measured in the coordinate system of the position of the collimator lens 22 and the focus offset. The predetermined search start position and the predetermined ratio K will be described later.

  Next, in step S12 (first approximate curve creation step), an approximate curve is created from the reproduction signal quality index measured at each of the three points M0, M1, and M2. This approximate curve is a curve indicating the value of the reproduction signal quality index with respect to the coordinate point indicating the relationship between the position of the collimator lens 22 and the focus offset. The approximation curve is created by a processing circuit provided in the main control circuit 16 shown in FIG.

  Next, in step S13 (first calculation step), the best point M3 at which the reproduction signal quality is the best is calculated from the approximate curve generated in step S12. The calculation of the best point M3 is performed by a processing circuit provided in the main control circuit 16 shown in FIG.

  Next, the procedure of the second search step (step S4) will be described. FIG. 4C is a flowchart showing the procedure of the second search step in the spherical aberration correction process and the focus offset adjustment process according to the present embodiment.

  As shown in FIG. 4C, first, in step S21, both the position of the collimator lens 22 and the focus offset at a predetermined ratio R with the best point M3 calculated in the first search step as a base point. To change. Then, the reproduction signal quality index is measured for each of combinations of three predetermined positions including the best point M3. In other words, the reproduction signal quality index for each of the three points M3, M4, and M5 is measured in the coordinate system of the position of the collimator lens 22 and the focus offset. The predetermined ratio R will be described later.

  Next, in step S22 (first approximate curve creation step), an approximate curve is created from the reproduction signal quality index measured at each of the three points M3, M4, and M5. This approximate curve is a curve indicating the value of the reproduction signal quality index with respect to the coordinate point indicating the positional relationship between the position of the collimator lens 22 and the focus offset. The approximation curve is created by a processing circuit provided in the main control circuit 16 shown in FIG.

  Next, in step S23 (first calculation step), the best point M6 at which the reproduction signal quality is the best is calculated from the approximate curve generated in step S22. The calculation of the best point M6 is performed by a processing circuit provided in the main control circuit 16 shown in FIG.

  Next, the measurement location of the reproduction signal quality index in the first search step and the second search step will be described in more detail with reference to FIGS. FIG. 5 is a graph for explaining the measurement points of the reproduction signal quality index in the first search step and the second search step. FIG. 5A is a graph (first contour map) showing a simulation result of the characteristics of the RF signal amplitude (RF amplitude) with respect to the focus offset and the position of the collimating lens 22, and FIG. It is a graph (2nd contour map) which shows the simulation result of the characteristic of tracking error signal amplitude (PP amplitude) to offset and a collimating lens position. Note that the graphs shown in FIGS. 5A and 5B show the simulation results of the RF signal amplitude and tracking error signal amplitude with respect to the position of the collimator lens 22 and the focus offset, respectively. The optical system used for the simulation is the optical system of the optical pickup 2 shown in FIG. The simulation is a simulation when the RF signal, tracking error signal, and focus error signal are calculated and created as described above. 5A and 5B, the horizontal axis is the position of the collimating lens 22, the vertical axis is the focus offset, and the RF amplitude and tracking error signal amplitude are shown as contour maps. The value on the vertical axis represents the focus offset as a ratio (%) of the offset amount to the tracking error signal amplitude.

  As shown in FIGS. 5A and 5B, the RF signal amplitude and the tracking error signal amplitude have similar characteristics, and the slopes of the ridge lines are almost the same in the contour map. Note that the “ridge line” refers to a straight line existing in a region where the value of the reproduction signal quality index or the amplitude of the tracking error signal is highest in the contour map. FIG. 5A shows the result of a simulation of the RF signal amplitude as the reproduction signal quality index, but the same result is obtained even when the jitter of the reproduced RF signal is used as the reproduction signal quality index. That is, the jitter distribution of the RF signal and the tracking error signal amplitude have similar characteristics, and the slopes of the ridge lines are almost the same in the contour map. Such a result is a characteristic of the optical information recording apparatus 100 when the focus error signal is generated by the knife edge method using the hologram element 28 having the hologram pattern shown in FIG.

  As described above, the RF signal amplitude and the tracking error signal amplitude have similar characteristics. Therefore, in the first search step, in the RF signal amplitude contour map shown in FIG. 5A, the position of the collimating lens 22 and the focus offset are simultaneously changed so as to follow the inclination of the ridge line, while the reproduction signal quality is changed. The best point of the index (here, RF signal amplitude) is searched. As a result, unstable tracking servo control due to a decrease in the amplitude of the tracking error signal can be avoided, and a stable search for the reproduction signal quality index becomes possible. Hereinafter, the change direction of the coordinate point of the collimator lens 22 and the focus offset in the contour map will be referred to as a first search direction. The first search direction coincides with the direction of the ridgeline in the contour map, and is indicated by a dotted line in FIGS. 5 (a) and 5 (b).

  Here, the search start point in the first search step does not necessarily exist on the edge of the contour map of the RF signal amplitude due to an assembly error of the optical pickup 2 or the like. For this reason, the first search step alone does not reach the best point on the contour map of the RF signal amplitude.

  Therefore, in the second search step, the position of the collimator lens 22 and the focus offset are simultaneously changed in the contour map in accordance with a direction (second search direction) orthogonal to the first search direction (dotted line direction). However, the best point of the reproduction signal quality index (here, the RF signal amplitude) is searched. As described above, since the RF signal amplitude and the tracking error signal amplitude have similar characteristics, the second search direction is a direction in which the fluctuation of the tracking error signal amplitude increases. Therefore, in the second search step, it is necessary to make the search range, that is, the position of the collimating lens 22 and the fluctuation range of the focus offset narrower than those in the first search step so that the tracking control does not become unstable. . On the other hand, the second search direction is also a direction in which the fluctuation of the RF signal amplitude increases. Therefore, even if the search range in the second search direction becomes narrow as described above, it is possible to search for the best point without any problem.

  5 (a) and 5 (b) show examples in which the RF signal amplitude is used as the reproduction signal quality index, the present invention is not limited to this. As a reproduction signal quality indicator, jitter of the reproduction signal may be used in addition to the RF signal amplitude. Jitter here means a physical quantity representing a time lag of information transition in a reproduction signal. Jitter is closely related to an error rate that indicates the probability of an error when reading information from an optical disc. For this reason, the jitter is used as an evaluation value for control in the optical information recording apparatus.

  The inventor of the present application conducted an experiment to search for the best point of jitter by the first search step and the second search step, using the jitter of the playback signal as the playback signal quality. FIG. 6 is a graph for explaining an experimental result by the present inventor. FIG. 6A is a graph (first contour map) showing the characteristics of the jitter of the RF signal with respect to the focus offset and the position of the collimating lens 22 in a contour map in the optical information recording apparatus 100. FIG. b) is a graph (second contour map) showing an experimental result of the tracking error signal amplitude (PP amplitude) with respect to the focus offset and the collimating lens position in the optical information recording apparatus 100 as a contour map. 6A and 6B, the horizontal axis is the position of the collimating lens 22, and the vertical axis is the focus offset.

  In the contour maps of FIGS. 6A and 6B, the first search step is indicated by a straight line T1, and the second search step is indicated by a straight line T2. Further, the first search direction in which the search is performed in the first search step is the direction of the straight line T1, and the second search direction in which the search is performed in the second search step is the direction of the straight line T2.

  In the first search step, first, the jitter of the reproduction signal at a point M0 which is a predetermined search start point is measured. Here, the setting method of the point M0 which is a search start point is demonstrated.

  First, when the search start point is uniformly set to a fixed point M0 for all the optical pickups 2 to be searched for searching for the jitter of the reproduction signal, the following problem occurs. That is, due to variations in the assembly of the optical systems of the individual optical pickups 2, there may occur cases where tracking control becomes unstable at the start of search or tracking control becomes impossible. Therefore, in the optical information recording apparatus 100, in the assembly process of the optical pickup 2, a memory that records the collimating lens position that becomes parallel light when the light beam from the laser generating element 21 passes through the collimating lens 22 as parallel light position data. Is built in the main control circuit 16. When spherical aberration correction and focus offset adjustment are performed in the first search step, the search starts at the position (point M0) where the collimator lens 22 is moved by a predetermined amount from the parallel light position data recorded in the memory. It becomes a point. Specifically, the search start point is a position calculated by moving from the parallel light position recorded in the memory so that the spherical aberration is minimized when the information recording surface of the disc is focused. That is, a value obtained by adding a certain calculated value to the parallel light position recorded in the memory when the optical pickup is assembled is set as a search start point. When searching for the best point of the reproduction signal quality index, if the same search start point is set for all the optical pickups 2 to be searched, the search for the best point becomes unstable due to variations in the assembly of the optical system. Exists. On the other hand, there is little variation from the parallel light position to the position where the spherical aberration is minimized. Therefore, a stable reproduction signal quality index can be obtained by setting the position calculated so that the spherical aberration is minimized when moving from the parallel light position and focusing on the information recording surface of the disc as the search start point. The best point search can be realized.

  Note that the optimal movement amount (predetermined amount) for moving the collimator lens 22 varies depending on the design of the optical system of the optical pickup 2 to be searched, and therefore may be appropriately determined from simulation results and experimental results. For example, the parallel light position of the collimating lens 22 is designed so that the optical pickup 2 is compatible with a two-layer disc, and the laser beam is focused at an intermediate position between the first layer and the second layer. Think about the case. In this case, when performing spherical aberration correction and focus offset adjustment on the first layer, a predetermined amount for moving the collimator lens 22 may be set to 0.8 mm to 1.2 mm on the light source side.

  As a result, variations due to the assembly error of the optical pickup 2 can be eliminated, so that a more stable search is possible as compared with a method in which the search start point is set to a certain value.

  As described above, after setting the point M0 that is the search start point, both the position of the collimating lens 22 and the focus offset are changed at a predetermined ratio K. Then, the jitter of the reproduced signal at points M1 and M2 is measured. The point M1 at which the jitter of the reproduction signal is measured is a position where both the collimating lens position and the focus offset are reduced by the ratio K with the point M0 as the base point in the contour maps of FIGS. 6 (a) and 6 (b). ing. Further, the point M2 is a position where both the collimating lens position and the focus offset are increased by the ratio K with the point M0 as the base point in the contour maps of FIGS. 6 (a) and 6 (b).

  The predetermined ratio K corresponds to the slope of the straight line T1 in the contour maps of FIGS. 6 (a) and 6 (b). The ratio K (that is, the slope of the straight line T1) is ideally the slope of the ridgeline (dotted line) of the contour map of FIGS. 5A and 5B obtained from the simulation results. However, when performing the actual adjustment, it is necessary to set the predetermined ratio K in consideration of various error factors of the optical pickup 2.

  Regarding the ratio K, for example, the contour map (first contour map) in FIG. 6A showing the characteristics of the jitter of the reproduction signal with respect to the position and focus offset of the collimator lens 22, and the position and focus offset of the collimator lens 22. This can be determined based on the contour map (second contour map) of FIG. 6B showing the amplitude characteristic of the tracking error signal.

  That is, among the arbitrary straight lines extending along the ridgeline of the contour map of FIG. 6A, the slope of the straight line T1 that is most parallel to the ridgeline of the contour map of FIG.

  Here, in the contour maps of FIGS. 5A and 5B, the focus offset on the vertical axis is not the actual movement amount of the objective lens 26 but the ratio of the offset injection voltage to the amplitude of the focus error signal (%). ). This is because the focus offset cannot be managed by the position (μm) of the objective lens 26 when performing spherical aberration correction and focus offset adjustment in the optical pickup 2. Therefore, the voltage (focus offset injection voltage) injected into the objective lens actuator 27 is managed. The focus offset injection voltage varies in the actual focus male set amount due to variations in sensitivity and gain of the photodetector that detects the focus error signal, and variations in sensitivity of the actuator 27 for the objective lens. Therefore, by managing the focus offset amount (%) based on the ratio of the focus offset injection voltage to the focus error signal amplitude, it is possible to eliminate an error factor of the focus offset amount due to variations in photodetector sensitivity and gain.

  Errors due to assembly errors of the optical system of the optical pickup 2 cannot be eliminated. For this reason, when the adjustment is actually performed, the ratio K may be set by adding the actual measurement result to the simulation result for the optical pickup 2 designed individually. When the inclination K was obtained from the simulation result with the optical pickup designed by the present inventor, K = 55 was calculated.

  In the first search step, an approximate curve of the jitter of the reproduction signal is created from the three points M0, M1, and M2 measured as described above (step S12 in FIG. 4B). Then, the best point in the first search step is calculated from the approximate curve (step S13 in FIG. 4B). This best point is defined as a point M3.

  As shown in FIG. 6B, in the first search direction (the direction of the straight line T1) in which the search is performed in the first search step, the change in the amplitude is small in the contour map of the tracking error signal amplitude. ing. In this way, in the first search step, the first search direction is set as the ridge line direction of the contour map of the jitter of the reproduction signal, and as a result, the search is performed in the ridge line direction of the contour map of the tracking error signal. Become. For this reason, the change in the amplitude of the tracking error signal is small, and the servo control error due to the decrease in the amplitude is rare.

  In order to improve the search accuracy of the point M3, which is the best point, a plurality of points may be measured at the predetermined ratio K described above. However, in order to shorten the adjustment time, the measurement may be performed at three points including the point M0 that is the search start point.

  Next, the search procedure of the second search step will be described. The second search step is represented by a straight line T2 in FIGS. 6 (a) and 6 (b).

  In the second search step, both the position of the collimating lens 22 and the focus offset are changed at a predetermined ratio R. Then, the jitter of the reproduced signal at points M4 and M5 is measured. The point M4 at which the jitter of the reproduction signal is measured is obtained by reducing both the collimating lens position and the focus offset by a ratio R from the point M3 which is the best point in the contour maps of FIGS. 6 (a) and 6 (b). It is in the position. Further, the point M5 is a position where both the collimating lens position and the focus offset are increased by the ratio R with respect to the point M3 which is the best point in the contour maps of FIGS. 6 (a) and 6 (b). Yes.

  The ratio R corresponds to the slope of the straight line T2 in the contour map shown in FIGS. 6 (a) and 6 (b). As shown in FIGS. 6A and 6B, the direction of the straight line T2 (second search direction) is orthogonal to the direction of the straight line T1 (first search direction). The straight line T2 passes through the point M3 which is the best point calculated in the first search step.

  Here, the ratio R (that is, the slope of the straight line T2) is ideally orthogonal to the ridgeline (dotted line) of the contour map of FIGS. 5A and 5B obtained from the simulation results. The slope of the straight line. That is, the ratio K for changing both the position and the focus offset of the collimating lens 22 in the first search step and the ratio R for changing both the position and the focus offset of the collimating lens 22 in the second search step. In the meantime, the relational expression “K × R = −1 (ie, R = −1 / K)” holds. However, when the adjustment is actually performed, it is preferable to set the ratio R by adding the actual measurement result to the simulation result for the optical pickup 2 designed individually. When the ratio R was obtained from the simulation results with the optical pickup designed by the present inventor, R = −0.018 was calculated.

  In the second search step, an approximate curve of the jitter of the reproduction signal is created from the three points M3, M4, and M5 measured as described above (step S32 in FIG. 4C). Then, the best point in the second search step is calculated from the approximate curve (step S33 in FIG. 4B). The best point M6 calculated in this way is the optimum value of the collimating lens position and the focus offset in the optical pickup 2.

  As shown in FIG. 6B, in the second search step, the search is performed in a direction in which the amplitude change of the tracking error signal is large. For this reason, the search range (the width of the straight line T2) needs to be narrower than the search range (the width of the straight line T1) in the first search step so that tracking control does not become unstable. However, in the second search direction (the direction of the straight line T2), since the change in the jitter of the reproduction signal is large, it is possible to find the best point M6 even if the search range is narrowed.

  Next, the jitter search range of the reproduction signal in the first search step and the second search step will be described using the experiment results of the inventors of the present application shown in FIGS. 6 (a) and 6 (b). .

  In order to find the best point from the approximated curve of the measured reproduction signal quality (jitter) with high accuracy, the search range should be as large as possible. However, if the search range is widened, the amplitude of the tracking error signal becomes small and the tracking control becomes unstable. Therefore, in the first search step and the second search step, as a search range, the reproduction signal jitter has a sufficient difference to draw an approximate curve between the measurement points, and the tracking error signal amplitude is servo-controlled. It suffices to set a range that is large enough to perform.

  The first search step is a search in a direction in which the change in the tracking error signal amplitude is small. On the other hand, the second search step is a search in a direction in which the change in the tracking error signal amplitude is large. For this reason, in the 2nd search step, it is good to narrow a search range rather than the 1st search step.

  In the experiments of the present inventors shown in FIG. 6A and FIG. 6B, the adjustment range of the position of the collimating lens 22 in the first search step is ± 0.29 μm, and the collimating lens 22 in the second search step. The position adjustment range was set to ± 0.14 μm. Even if the difference in jitter measured in each search step is 0.5% or more, and the ridge line of the jitter and tracking error signal amplitude distribution is shifted by ± 0.16 μm in the collimating lens position direction due to assembly error or the like, The range of decrease in the amplitude of the tracking error signal is within 20%.

  As a result, it is possible to search for the best point of jitter with high accuracy using an approximate curve, and to search without making tracking control unstable. The search range is an adjustment range determined for the optical system of the optical pickup 2, and does not limit the search ranges of the first search step and the second search step in the present invention. In order to implement the spherical aberration correction method and the focus offset adjustment method of the present invention in another optical pickup, the range must be determined in consideration of the respective jitter characteristics and assembly errors.

  In addition, in order to improve the search accuracy, it is possible to perform jitter measurement at three or more points on the contour map of the reproduction signal quality index. Even when three or more jitter measurements are performed, the measurement is performed within the above-described search range.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIGS. According to the method of the present embodiment, it is possible to realize a spherical aberration correction and focus offset adjustment method capable of further improving the adjustment accuracy without causing problems such as a servo control error during adjustment.

  Note that the configuration of the optical information recording apparatus 100 according to the present embodiment is the same as that of the first embodiment, and a description thereof will be omitted. Further, the basic sequence of the optical information processing method of the present embodiment follows the flowchart shown in FIG.

  The first search step and the second search step in the present embodiment will be described with reference to FIGS. FIG. 7 is a flowchart showing the procedure of the first search step and the second search step of the spherical aberration correction process and the focus offset adjustment process according to the present embodiment, and FIG. The procedure of the search step is shown, and FIG. 7B shows the procedure of the second search step.

  First, in the first search step, step S31 is executed as shown in FIG. In step S31, both the position of the collimating lens 22 and the focus offset are changed at a predetermined ratio K. Then, the jitter of the reproduced signal is measured at the three changed points M10, M11, and M12. In step S31, the setting of the point M10, which is the search start point, is the same as in the first embodiment, and a description thereof will be omitted. The method for setting the “predetermined ratio K” is the same as that in the first embodiment, and a description thereof is omitted.

  Next, in step S32 (comparison step), the measured jitter of the reproduced signal is compared. This comparison is performed by comparing the jitter value J11 at the point M11 with the jitter value J12 at the point M12.

  If the comparison result satisfies | J11−J12 |> 0.5 [%] and J11> J12, the process proceeds to step S33. If the comparison result satisfies | J11−J12 |> 0.5 [%] and J11 <J12, the process proceeds to step S34. If the comparison result satisfies | J11−J12 | ≦ 0.5 [%], the process proceeds to step S35.

  In step S33 (additional measurement step), the jitter of the reproduced signal at points M13 and M14 is additionally measured. Here, the points M13 and M14 are M13 = M12 + addition value α and M14 = M13 + addition value α. The addition value α is a constant value to be added (subtracted) to the position of the collimator lens 22 and the focus offset at a predetermined ratio K. Thereafter, the process proceeds to step S36.

  In step S34 (additional measurement step), the jitter of the reproduction signal at points M13 and M14 is additionally measured. Here, the points M13 and M14 are M13 = M11−addition value α and M14 = M13−addition value α. Thereafter, the process proceeds to step S36.

  In step S35 (additional measurement step), the jitter of the reproduction signal at points M13 and M14 is additionally measured. Here, the points M13 and M14 are M13 = M11−addition value α and M14 = M12 + addition value α. Thereafter, the process proceeds to step S36.

  In step S36 (second approximate curve creating step), an approximate curve is created from the jitter of the reproduced signal at the five points M10 to M14 measured as described above. This is performed by a processing circuit provided in the main control circuit 16 shown in FIG. 1 as in the first embodiment.

  In step S37 (second calculation step), the best point M15 is calculated from the approximate curve created in step 36. This is performed by a processing circuit provided in the main control circuit 16 shown in FIG.

  Next, the procedure of the second search step will be described. FIG. 7B is a flowchart showing the procedure of the second search step of the spherical aberration correction process and the focus offset adjustment process according to the present embodiment.

  As shown in FIG. 7B, first, in step S41, both the position of the collimator lens 22 and the focus offset at a predetermined ratio R with the best point M15 calculated in the first search step as a base point. To change. Then, the jitter of the reproduction signal is measured at the three changed points M15, M16, and M17. The method of setting “predetermined ratio R” is the same as that in the first embodiment, and thus the description thereof is omitted. The point M16 at which the jitter of the reproduction signal is measured is obtained by decreasing both the collimating lens position and the focus offset by the ratio R from the point M15 which is the best point in the contour maps of FIGS. 8 (a) and 8 (b). It is in the position. Further, the point M17 is a position where both the collimating lens position and the focus offset are increased by the ratio R with respect to the point M15 which is the best point in the contour maps of FIGS. 8A and 8B. Yes.

  Next, in step S42, the jitter of the measured reproduction signal is compared. This comparison is performed by comparing the jitter value J16 at the point M16 with the jitter value J17 at the point M17.

  If the comparison result satisfies | J16−J17 |> 0.5 [%] and J16> J17, the process proceeds to step S43. If the comparison result satisfies | J16−J17 |> 0.5 [%] and J16 <J17, the process proceeds to step S44. If the comparison result satisfies | J16−J17 | ≦ 0.5 [%], the process proceeds to step S45.

  In step S43, the jitter of the reproduction signal at the point M18 is additionally measured. Here, the point M18 is M18 = M17 + added value β. The addition value β is a constant value that increases or decreases the collimating lens position and the focus offset at a predetermined ratio R. Thereafter, the process proceeds to step S45.

  In step S44, the jitter of the reproduction signal at the point M18 is additionally measured. Here, the point M18 is M18 = M16−addition value β. Thereafter, the process proceeds to step S45.

  In step S45, an approximate curve is created from the jitter of the reproduced signal at the four points M15 to M18 measured as described above. This is performed by a processing circuit provided in the main control circuit 16 shown in FIG. 1 as in the first embodiment.

  In step S46, the best point M19 is calculated from the approximate curve created in step 45. This is performed by a processing circuit provided in the main control circuit 16 shown in FIG.

  Next, the measurement location of the reproduction signal quality index in the first search step and the second search step will be described in more detail with reference to FIG. FIG. 8 is a graph for explaining the experimental results by the present inventor. FIG. 8A shows a contour map of the jitter characteristics of the RF signal with respect to the focus offset and the position of the collimating lens 22. FIG. 8B is a graph showing an experimental result of the tracking error signal amplitude (PP amplitude) with respect to the focus offset and the position of the collimating lens 22 as a contour map. In FIGS. 8A and 8B, the horizontal axis is the position of the collimating lens 22, and the vertical axis is the focus offset.

  In the contour maps of FIGS. 8A and 8B, the search range in the first search step is indicated by a straight line T11, and the search range in the second search step is indicated by a straight line T12. Yes. The first search direction for searching in the first search step is the direction of the straight line T11, and the second search direction for searching in the second search step is the direction of the straight line T12. In the present embodiment, the first search step and the second search step each have a branch point in the flow, and there are a plurality of procedures according to the comparison result of the jitter measurement of the first reproduction signal. FIG. 8 shows an example of the plurality of procedures.

  In the first search step, first, the jitter of the reproduction signal at the point M10 in the contour map is measured. A point M10 is a search start point, and the setting method is the same as that in the first embodiment, and thus the description thereof is omitted.

  Subsequently, by changing the position of the collimator lens 22 and the focus offset at a predetermined ratio K, the jitter of the reproduction signal at the points M11 and M12 is measured. The point M11 at which the jitter of the reproduction signal is measured is a position where both the collimator lens position and the focus offset are reduced by the ratio K with respect to the point M10 in the contour maps of FIGS. 8 (a) and 8 (b). ing. Further, the point M12 is a position where both the collimating lens position and the focus offset are increased by the ratio K with the point M10 as a base point in the contour maps of FIGS. 8A and 8B.

  In the present embodiment, the positional relationship between the three points M10, M11, and M12 in the contour map is such that M11 = M10−addition value α and M12 = M10 + addition value α. Here, the addition value α is a constant value that is added (subtracted) to the collimating lens position and the focus offset at a predetermined ratio K. In the contour maps shown in FIGS. 8A and 8B, for example, when a change from the point M10 to the point M11 is considered, the addition value α is the subtraction amount a of the collimator lens position at the point M10, and the point A combination of the focus offset subtraction amount b in M10 can be used. The added value α is adjusted so that the ratio of the added value of the focus offset to the added amount of the collimating lens position becomes a predetermined ratio K. The predetermined ratio K is the same as that in the first embodiment, and thus the description thereof is omitted.

  The added value α will be described in more detail with reference to FIGS. 8A and 8B. In order to find the best point accurately from the approximate curve of the jitter of the reproduced signal to be measured, it is better to increase the added value α and widen the search range. However, if the search range is widened, the tracking error signal amplitude becomes small and the tracking control becomes unstable. Therefore, in the first search step and the second search step, the jitter of the reproduced signal has a sufficient difference between the measurement points to draw an approximate curve, and the tracking error signal amplitude is servo-controlled in the entire search range. A range that is large enough to perform the above may be set as the search range. The first search step is a search in a direction in which the change in the tracking error signal amplitude is small. On the other hand, the second search step is a search in a direction in which the change in the tracking error signal amplitude is large. For this reason, in the 2nd search step, it is good to narrow a search range rather than the 1st search step.

  8A and 8B, the addition value α (“a” shown in FIG. 8) of the collimating lens position is set to 0.14 μm. At this time, the focus offset addition value α (“b” shown in FIG. 8) is 7.9% so as to follow a predetermined ratio K. The addition value α of the collimating lens position and the focus offset may be set so as to satisfy the following conditions (1) and (2). (1) The difference between the maximum value and the minimum value of jitter at all measurement points including the jitter measurement point added in the first search step is 0.5% or more. (2) Even if the ridgeline of the reproduction signal jitter and tracking error signal amplitude distribution is shifted by ± 0.16 μm in the direction of the collimating lens due to assembly errors, the tracking error signal amplitude is 80% or more of the maximum amplitude at all measurement points. Is set to the range.

  By satisfying the above conditions (1) and (2), the best point can be searched stably and accurately. Note that the addition value α is a value determined for the optical system of the optical pickup 2 and does not limit the addition value α used in the first search step in the present embodiment. In order to implement the spherical aberration correction method and the focus offset adjustment method of the present invention in another optical pickup, the added value α must be determined in consideration of the respective jitter characteristics and assembly errors.

  In the next step (step S32), the jitter value J11 at the point M11 is compared with the jitter value J12 at the point M12. By comparing the jitter values, it is possible to determine the addition of the measurement points for the jitter of the reproduction signal in accordance with the deviation of the jitter distribution due to the assembly error of each optical pickup and the tolerance of parts. A more accurate and stable search is possible.

  In the first search step, classification is performed according to the following three conditions according to the comparison result. The three conditions are: | J11−J12 |> 0.5 and J11> J12, | J11−J12 |> 0.5 and J11 <J12, and | J11−J12 | ≦ 0. 5 is satisfied.

  When | J11−J12 |> 0.5 and J11> J12 are satisfied, it is estimated that the best point of the jitter of the reproduction signal is that the collimating lens position is on the plus side of the point M12. Therefore, it is preferable to add the measurement points M13 and M14 on the plus side of the point M12. Therefore, in this condition, the additional measurement points M13 and M14 are M13 = M12 + addition value α and M14 = M13 + addition value α.

  When | J11−J12 |> 0.5 and J11 <J12 are satisfied, it is estimated that the best point of the jitter of the reproduction signal is that the collimating lens position is on the minus side of the point M11. Therefore, the measurement points M13 and M14 may be added on the minus side of the point M11. Therefore, in this condition, the additional measurement points M13 and M14 are M13 = M11−addition value α and M14 = M13−addition value α.

  When | J11−J12 | ≦ 0.5 is satisfied, it is estimated that the best point of the jitter of the reproduction signal is between the point M11 and the point M12. Therefore, the measurement point M13 may be added to the minus side of the collimating lens position from the point M11, and the measurement point M14 may be added to the plus side of the collimating lens position from the point M12. Therefore, in this condition, the additional measurement points M13 and M14 are M13 = M11−addition value α and M14 = M12 + addition value α. In the example shown in FIG. 8, the relationship between measurement points under this condition is shown.

  In the next step (step S36), approximate curves are created from the jitter of the reproduced signal at the points M10, M11, and M12 measured first and the points M13 and M14 measured additionally. Then, the best point M15 in the first search step is calculated from the approximate curve (step S37).

  Next, the search procedure of the second search step will be described. The second search step is indicated by a straight line T12 in the contour map of FIGS. 8 (a) and 8 (b).

  In the second search step, both the position of the collimating lens 22 and the focus offset are changed at a predetermined ratio R. Then, the jitter of the reproduced signal at points M16 and M17 is measured. The point M16 at which the jitter of the reproduction signal is measured is obtained by decreasing both the collimating lens position and the focus offset by the ratio R from the point M15 which is the best point in the contour maps of FIGS. 8 (a) and 8 (b). It is in the position. Further, the point M17 is a position where both the collimating lens position and the focus offset are increased by the ratio R with respect to the point M15 which is the best point in the contour maps of FIGS. 8A and 8B. Yes.

  Here, in this embodiment, the positional relationship between the three points M15, M16, and M17 in the contour map is such that M16 = M15−addition value β and M17 = M15 + addition value β. Here, the addition value β is a constant value that is added (subtracted) to the collimator lens position and the focus offset at a predetermined ratio R. In the contour maps shown in FIGS. 8A and 8B, for example, when a change from the point M15 to the point M17 is considered, the addition value β is an addition amount a ′ of the collimating lens position at the point M15, and The focus offset subtraction amount b 'at the point M15 can be combined. The added value β is adjusted so that the ratio of the added value of the focus offset to the added amount of the collimating lens position becomes a predetermined ratio R. The predetermined ratio R is the same as that in the first embodiment, and thus the description thereof is omitted.

  The added value β will be described in more detail with reference to FIGS. 8A and 8B. In the example of the experiment of the present inventor shown in FIGS. 8A and 8B, the addition value β (“a ′” shown in FIG. 8) of the collimating lens position is set to 0.072 μm. The added value β (“b ′” shown in FIG. 8) of the focus offset was set to −0.013% so as to follow the ratio R.

  The addition value β of the collimating lens position and the focus offset may be set so as to satisfy the following conditions (1) and (2). (1) In the second search step, the difference between the maximum value and the minimum value of jitter at all measurement points including additional measurement points is 0.5% or more. (2) Even if the edge of the jitter and tracking error signal amplitude distribution is shifted by ± 0.16 μm in the collimating lens position direction due to assembly errors, etc., the tracking error signal amplitude is within 80% of the maximum amplitude at all measurement points. Set.

  By satisfying the above conditions (1) and (2), the best point can be searched stably and accurately. Note that the addition value β is a value determined for the optical system of the optical pickup 2 and does not limit the addition value β used in the second search step in the present embodiment. In order to implement the spherical aberration correction method and the focus offset adjustment method of the present invention in another optical pickup, the added value β must be determined in consideration of the respective jitter characteristics and assembly errors.

  In the next step (step S41), the jitter value J16 at the point M16 is compared with the jitter value J17 at the point M17. By comparing the jitter values, it is possible to determine the addition of the measurement points for the jitter of the reproduction signal in accordance with the deviation of the jitter distribution due to the assembly error of each optical pickup and the tolerance of parts. A more accurate and stable search is possible.

  In the second search step, classification is performed under the following three conditions. The first condition is when | J16-J17 |> 0.5 and J16> J17, and the second condition is when | J16-J17 |> 0.5 and J16 <J17. This is a case where the third condition satisfies | J16−J17 | ≦ 0.5.

  When | J16−J17 |> 0.5 and J16> J17 are satisfied, it is estimated that the best point of the jitter of the reproduction signal is that the collimating lens position is on the plus side of the point M17. Therefore, the measurement point M18 may be added on the plus side of the point M17. Therefore, in this condition, the additional measurement point M18 is set to M18 = M17 + added value β. In the example shown in FIG. 8, the relationship between measurement points under this condition is shown.

  When | J16−J17 |> 0.5 and J16 <J17 are satisfied, it is estimated that the best point of the jitter of the reproduction signal is that the collimating lens position is on the minus side of the point M16. Therefore, it is preferable to add the measurement point M18 on the minus side of the point M16. Therefore, in this condition, the additional measurement point M18 is M18 = M16−addition value β.

  When | J16−J17 | ≦ 0.5 is satisfied, the best point of the jitter of the reproduction signal is estimated to be between the point M11 and the point M12. Therefore, under this condition, the process proceeds to the next step S45 without performing additional measurement.

  In the next step (step S45), an approximate curve is created from the jitter of the reproduced signal at each of the first measured points M15, M16, M17 and the additionally measured point M18. Then, the best point M19 in the second search step is calculated from the approximate curve (step S46). The best point M19 is the final value of the collimating lens position and the focus offset.

(Another expression)
The present invention can be expressed as the following (1) to (8).

  (1) An optical pickup that irradiates a focused light beam onto an optical recording medium and reads recorded information by the amount of light reflected from the optical recording medium, and is generated in the light beam irradiated onto the optical recording medium Spherical aberration correction means comprising a correction optical system for correcting spherical aberration, a correction optical system driving unit for driving the correction optical system, and a position sensor for detecting the position or initial position of the correction optical system, and the light beam on the signal recording surface A spherical aberration correction and focus offset adjustment method for an optical pickup comprising a focus offset adjustment means for adjusting an offset amount in the optical axis direction so as to be focused, and the step of irradiating the optical beam onto the optical recording medium A step of executing focus control and tracking control, and the spherical aberration correcting means and the focus offset adjusting means. The first search step of searching for the best position of the reproduction signal quality while simultaneously operating at a predetermined ratio from the search start position of the first, the spherical aberration correcting means, and the focus offset adjusting means, the best search of the first search An optimum spherical aberration correction position and an optimum focus offset position are determined by a second search step of searching for the best position of reproduction signal quality while simultaneously operating in a direction orthogonal to the first search through the position. And spherical aberration correction and focus offset adjustment method of the optical pickup.

  (2) In the operation of the spherical aberration correction means, the search for the first search is started at a position moved by a predetermined amount from the position adjusted so that the light beam passing through the correction optical system becomes parallel light. The spherical aberration correction and focus offset adjustment method of the optical pickup according to (1), wherein the position is a position.

  (3) The first search and the second search are a step of measuring reproduction signal quality at at least three locations, a step of creating an approximate curve from the measurement result, and a step of calculating the best position from the approximate curve The spherical aberration correction and focus offset adjustment method of the optical pickup according to (1) or (2), characterized by comprising:

  (4) The first search and the second search are performed by measuring at least three reproduction signal qualities, comparing the measured reproduction signal quality, and at least one location based on the comparison result. The light according to (1) or (2), further comprising: a step of additionally measuring the reproduction signal quality of: a step of creating an approximate curve from the measurement result; and a step of calculating a best position from the approximate curve. A method for correcting spherical aberration and adjusting a focus offset of a pickup.

  (5) The search for the best point of the reproduced signal quality uses an index that minimizes the jitter of the reproduced signal, and the optical pickup according to any one of (1) to (4) Spherical aberration correction and focus offset adjustment method.

  (6) The search for the best point of the reproduced signal quality uses an index that maximizes the amplitude of the reproduced signal. The optical pickup according to any one of (1) to (4), Spherical aberration correction and focus offset adjustment method.

  (7) The optical pickup according to any one of (1) to (4), wherein the search for the best point of the reproduced signal quality uses as an index the minimum error rate of the reproduced signal. Spherical aberration correction and focus offset adjustment method.

  (8) An optical information recording apparatus comprising the spherical aberration correction and focus offset adjustment functions according to any one of (1) to (7).

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be applied to an optical pickup compatible with various optical disks such as CD, DVD, and BD. Further, the present invention can be applied to an optical pickup having a plurality of objective lenses and corresponding to several types of optical disks.

  In addition, by applying the present invention to an optical information recording apparatus such as a DVD recorder or a BD recorder, an optical information recording apparatus capable of accurate adjustment in a short time can be provided.

DESCRIPTION OF SYMBOLS 1 Optical information processing part 11 Focus error generation circuit 12 Tracking error generation circuit 13 RF signal generation circuit 14 Servo control circuit (servo control part)
15 Collimating lens driving circuit 16 Main control circuit 2 Optical pickup 21 Laser generating element (light source)
22 Collimating lens (correcting optical member)
23 Collimating Lens Actuator 24 Position Sensor 25 1/4 Wave Plate 26 Objective Lens (Condensing Member)
27 Actuator for Objective Lens 28 Hologram Element 29 Optical Beam Splitter 30 Photodetector 3 Spindle Motor 4 Optical Disk 100 Optical Information Recording Device

Claims (8)

Light that irradiates the optical recording medium with respect to an optical pickup that condenses the light beam emitted from the light source onto the optical recording medium by the condensing member and detects the light beam reflected from the optical recording medium as an optical information signal. Spherical aberration correction processing for correcting spherical aberration generated in the beam, and focus offset adjustment processing for adjusting the offset amount in the optical axis direction so that the light beam is focused on the signal recording surface of the optical recording medium with respect to the condensing member. In the optical information processing method to be performed,
Servo control step for executing focus servo control and tracking servo control based on the optical information signal,
Spherical aberration is detected as the position of the correction optical member for correcting spherical aberration, and the correction optical member and the correction optical member so that the ratio of the offset amount of the condensing member to the displacement amount of the correction optical member becomes a predetermined ratio K. A first search for a first best position of the correction optical member and the condensing member where the position of the condensing member is changed in parallel and the value of the signal quality index representing the quality of the optical information signal is the best. A search step of
With the first best position as a base point, the correction optical member and the condensing member have a predetermined ratio-1 / K so that the ratio of the offset amount of the condensing member to the displacement amount of the correction optical member is a predetermined ratio-1 / K. A second search step for searching for a second best position of the correction optical member and the light collecting member, wherein the position is changed in parallel and the value of the signal quality index is the best. Optical information processing method. In the first search step, a parallel light position when the light beam passing through the correction optical member becomes parallel light in the optical system including the light source and the correction optical member is stored.
In the optical pickup, the search start position is a position calculated so that spherical aberration is minimized when the correction optical member is moved from the parallel light position and focused on the signal recording surface of the optical recording medium. The optical information processing method according to claim 1. In the first search step and the second search step, the value of the signal quality index is measured by a combination of at least three or more positions of the correction optical member and the light collecting member,
The first search step and the second search step are respectively
A first approximate curve creating step of creating an approximate curve of a signal quality index with respect to the position of the correction optical member and the position of the light collecting member from the measurement result of each position combination;
3. The method according to claim 1, further comprising: a first calculation step of calculating a position of the correction optical member and the condensing member from which the value of the signal quality index is the best from the approximate curve. Optical information processing method. In the first search step and the second search step, the value of the signal quality index is measured by a combination of at least three or more positions of the correction optical member and the light collecting member,
The first search step and the second search step are respectively
A comparison step for comparing the signal quality index values measured at each position combination;
An additional measurement step of adding at least one combination of the position of the correction optical member and the position of the light collecting member on which the value of the signal quality index is to be measured based on the comparison result;
A second approximate curve creating step of creating an approximate curve of the signal quality index with respect to the position of the correction optical member and the position of the light collecting member from the measurement result of the signal quality index including the additional measurement step;
The method according to claim 1, further comprising: a second calculation step of calculating a position of the correction optical member and the light condensing member from which the value of the signal quality index is the best from the approximate curve. Optical information processing method. The signal quality index is the jitter of the playback signal,
The first search step and the second search step search for positions of the correction optical member and the condensing member that minimize the jitter value of the reproduction signal. The optical information processing method according to claim 1. The signal quality indicator is the amplitude of the reproduction signal,
The first search step and the second search step search for the position of the correction optical member and the condensing member that maximizes the amplitude value of the reproduction signal. The optical information processing method according to claim 1. The signal quality index is an error rate of the reproduction signal,
5. The position of the said correction | amendment optical member and the said condensing member in which the value of the error rate of the said reproduction signal becomes the minimum is searched in a 1st search step and a 2nd search step. The optical information processing method according to any one of the above. Light that irradiates the optical recording medium with respect to an optical pickup that condenses the light beam emitted from the light source onto the optical recording medium by the condensing member and detects an optical information signal from the light beam reflected from the optical recording medium. Spherical aberration correction processing for correcting spherical aberration generated in the beam, and focus offset adjustment processing for adjusting the offset amount in the optical axis direction so that the light beam is focused on the signal recording surface of the optical recording medium with respect to the condensing member. In an optical information recording apparatus having an optical information processing unit for performing,
The optical information processing unit
Based on the optical information signal, a servo control unit that performs focus servo control and tracking servo control,
Spherical aberration is detected as the position of the correction optical member for correcting spherical aberration, and the correction optical member and the correction optical member so that the ratio of the offset amount of the condensing member to the displacement amount of the correction optical member becomes a predetermined ratio K. A first search for a first best position of the correction optical member and the condensing member where the position of the condensing member is changed in parallel and the value of the signal quality index representing the quality of the optical information signal is the best. Perform the search step
With the first best position as a base point, the correction optical member and the condensing member have a predetermined ratio-1 / K so that the ratio of the offset amount of the condensing member to the displacement amount of the correction optical member is a predetermined ratio-1 / K. A second search step for searching for a second best position of the correction optical member and the light condensing member, wherein the position is changed in parallel and the value of the signal quality index is the best, is executed. Optical information recording device.

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