JP2007188632A - Optical information processing device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information processing device which reproduces a high-quality reproduction signal from an optical disk, and also provide an optical information processing method. <P>SOLUTION: The optical information processing device includes; an optical head which irradiates an optical information recording medium with light, converts the light reflected by the optical information recording medium to a head signal, and outputs the signal; a signal quality index detection device which detects a signal quality index representing the quality of the head signal, based on the head signal outputted from the optical head; and a two-dimensional seeking device which seeks a focus position and spherical aberration quantity, wherein a value of the signal quality index detected by the signal-quality index detection device is optimal, by changing the focus position and spherical aberration quantity of the light radiated to the optical information recording medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical information processing apparatus and an optical information processing method including an optical head that emits light to an optical information recording medium, converts light reflected by the optical information recording medium into a head signal, and outputs the head signal.

  An optical disc called a DVD (Digital Versatile Disk) is commercially available as a high-density, large-capacity optical information recording medium. Such an optical disc has been rapidly spreading recently as a recording medium for recording images, music, and computer data. In recent years, research on next-generation optical discs with higher recording density has been promoted in various places. The next generation optical disc is expected as a recording medium to replace the video tape of the mainstream VTR (Video Tape Recorder), and is being developed at a rapid pitch.

  As a means for increasing the recording density of the optical disc, there is a method of reducing the spot formed on the recording surface formed on the optical disc. By increasing the numerical aperture of the light irradiated from the optical head and shortening the wavelength of the irradiated light, the spot formed on the recording surface formed on the optical disk can be reduced.

  However, when the numerical aperture of the light emitted from the optical head is increased and the wavelength of the emitted light is shortened, the amount of spherical aberration caused by the error in the thickness of the protective layer formed on the optical disk increases rapidly. . Therefore, it is indispensable to provide means for correcting the amount of spherical aberration. A conventional optical information processing apparatus provided with means for correcting the spherical aberration will be described below.

  FIG. 15 is a block diagram showing a configuration of a conventional optical information processing apparatus 90, and FIG. 16 is a block diagram for explaining a configuration of an optical head 5 provided in the conventional optical information processing apparatus 90. The optical information processing apparatus 90 includes an optical head 5. The optical head 5 is provided with a semiconductor laser 123. The light beam 122 emitted from the semiconductor laser 123 passes through the prism 124 and is collimated by the condenser lens 13 to become a substantially parallel light beam.

  The light beam collimated by the condenser lens 13 passes through the concave lens and the convex lens provided in the spherical aberration correction device 7 and is reflected by the mirror 14. The light beam reflected by the mirror 14 is converged by the objective lens 9, forms a spot on the recording surface formed on the optical disc 6, and is reflected by the recording surface. The reflected light 33 reflected by the recording surface again passes through the objective lens 9, is reflected by the mirror 14, passes through the spherical aberration correction device 7, and is narrowed down by the condenser lens 13. The reflected light 33 focused by the condenser lens 13 is reflected by the prism 124 and passes through the hologram 115 provided for detecting the amount of spherical aberration and the cylindrical lens 116 provided for detecting the focus position. , Enters the photodetector 117.

  The photodetector 117 generates a head signal based on the incident reflected light 33 and outputs the head signal to the preamplifier 18. The preamplifier 18 generates and outputs a focus error signal FE according to the astigmatism method based on the head signal output from the photodetector 117 provided in the optical head 5. Further, as disclosed in JP-T-2001-507463, the focus error signal of the inner peripheral portion and the focus error signal of the outer peripheral portion of the reflected light 33 are individually detected, and based on the difference between the two. The preamplifier 18 generates and outputs a spherical aberration amount error signal SAE.

The focus error signal FE output from the preamplifier 18 is input to the signal amplitude measuring device 20 via the switch 28. The signal amplitude measuring device 20 measures the amplitude of the focus error signal FE and outputs the result as a detection signal FE _pp to the maximum amplitude searcher 21. The maximum amplitude searcher 21 outputs the spherical aberration compensation signal ΔSAE to the adder 26 so that the amplitude of the detection signal FE _pp becomes maximum.

The maximum amplitude searcher 21 uses the detection signal FE _pp as an evaluation value and searches for the spherical aberration amount so that the detection signal FE _pp becomes maximum. As a method for searching for such an optimal spherical aberration amount, for example, the spherical aberration amount compensation signal ΔSAE is slightly changed to slightly increase or decrease the spherical aberration amount, and the increase or decrease of the amplitude of the detection signal FE _pp at that time is examined. A method of changing the spherical aberration compensation signal ΔSAE in the direction in which the detection signal FE _pp increases can be used.

  Since the switch 27 is in the OFF state, the adder 26 outputs the spherical aberration amount compensation signal ΔSAE output from the maximum amplitude searcher 21 to the spherical aberration amount controller 12. The spherical aberration controller 12 changes the divergence degree of the luminous flux by changing the distance between the two lenses provided in the spherical aberration correction device 7 of the optical head 5, and the thickness error of the protective layer formed on the optical disk 6. In order to correct the spherical aberration amount caused by the spherical aberration amount compensation signal ΔSAE output from the adder 26, the spherical aberration amount correction actuator provided in the spherical aberration amount correction device 7 of the optical head 5 is used. 8 outputs a control signal.

  The preamplifier 18 amplifies the head signal output from the optical head 5, generates a reproduction signal RF, and outputs it to the jitter detector 4. The jitter measuring device 4 measures the jitter of the reproduction signal RF output from the preamplifier 18 and outputs the result to the minimum jitter searcher 91 as a jitter detection signal JT.

  Here, jitter refers to 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 processing apparatus.

  The minimum jitter searcher 91 searches for the focus position where the jitter value is minimum using the same method as the maximum amplitude searcher 21 described above, and outputs the focus position compensation signal ΔFE to the adder 25. The switch 28 switches to the adder 25, and the focus error signal FE output from the preamplifier 18 is output to the adder 25. The adder 25 adds the focus error signal FE output from the preamplifier 18 and the focus position compensation signal ΔFE output from the minimum jitter prober 91, and outputs the result to the focus controller 11. The focus controller 11 outputs a control signal to the focus actuator 10 provided in the optical head 5 based on the addition result output from the adder 25. The focus actuator 10 drives the objective lens 9 along the direction perpendicular to the optical disk 6 so as to control the focus position of the light beam that converges on the optical disk 6 based on the control signal output from the focus controller 11. . In this way, focus control is executed.

  Then, the switch 27 changes from off to on. The maximum amplitude searcher 21 outputs to the adder 26 a spherical aberration compensation signal ΔSAE that maximizes the amplitude of the focus error signal FE stored before execution of focus control. The adder 26 adds the spherical aberration amount error signal SAE output from the preamplifier 18 and the spherical aberration amount compensation signal ΔSAE output from the maximum amplitude searcher 21, and the result is sent to the spherical aberration amount controller 12. Output. Based on the addition result output from the adder 26, the spherical aberration amount controller 12 outputs a control signal to the spherical aberration amount correction actuator 8 provided in the spherical aberration amount correction device 7 of the optical head 5. The spherical aberration amount correcting actuator 8 is a spherical surface in order to correct the spherical aberration amount caused by the thickness error of the protective layer formed on the optical disc 6 based on the control signal output from the spherical aberration amount controller 12. The degree of divergence of the light beam is changed by changing the distance between the two lenses provided in the aberration correction device 7.

In the conventional optical disc apparatus, the spherical aberration amount is first corrected in this way, and then the focus position where the jitter value is minimized is searched.
JP-T-2001-507463

  However, in the conventional optical information processing apparatus configured as described above, it has been found by recent studies by the present inventors that the jitter does not necessarily converge to the minimum value.

  FIGS. 17A to 17C are graphs showing the relationship between the wavefront aberration and the distance from the center of the light beam. The horizontal axis indicates the distance from the center of the light beam that the optical head 5 irradiates the optical disc 6 with, and the vertical axis indicates the wavefront aberration. Since wavefront aberration is closely related to jitter, it is used to evaluate the optical performance of an optical head.

  FIG. 17A shows the relationship between the distance from the center of the light flux and the wavefront aberration when the focus position of the light flux is located slightly off the recording surface formed on the optical disc along the direction perpendicular to the surface of the optical disc. Shows the relationship between. As shown in FIG. 17A, the curve indicating the relationship between the distance from the center of the light beam and the wavefront aberration when the focus position of the light beam is shifted from the recording surface is a quadratic curve.

  FIG. 17B shows the distance from the center of the light beam and the wavefront aberration when the spherical aberration correction device 7 gives a spherical aberration of 20 mλ when the focus position is shifted from the recording surface as shown in FIG. Shows the relationship between. As is apparent from the curve shown in FIG. 17B, it can be seen that the total wavefront aberration amount is larger than the total wavefront aberration amount shown in FIG.

  FIG. 17C shows the distance from the center of the light beam when the spherical aberration correction device 7 gives spherical aberration of −20 mλ when the focus position of the light beam is shifted from the recording surface as shown in FIG. And the wavefront aberration. As is apparent from the curve shown in FIG. 17C, it can be seen that the total wavefront aberration amount is smaller than the total wavefront aberration amount shown in FIG.

  As described above, even when spherical aberration having the same absolute value is applied, the total wavefront aberration amount increases in the case of FIG. 17B and decreases in the case of FIG. 17C. This means that the focus position and the spherical aberration amount are influenced by each other, and the focus position and the spherical aberration amount are not independent of jitter.

  In the conventional optical information processing apparatus described above, the spherical aberration amount is first searched for the spherical aberration amount at which the amplitude of the focus error signal is maximized, and then the focus position at which the jitter value is minimized. And the focus position are independently explored.

  However, as described above, both the focus position and the spherical aberration amount affect the jitter. Therefore, when the focus position and the spherical aberration amount are independently searched, they depend on the initial focus position and the initial spherical aberration amount. Therefore, the convergence results in exploration may be different. As a result, there is a possibility that a search result in which the jitter becomes a true minimum value cannot always be obtained. If the jitter value obtained as a result of the search deviates from the true minimum value, there arises a problem that the quality of the reproduced signal deteriorates. Further, there is a possibility that the record information and address information recorded on the optical disc cannot be read normally. Furthermore, when recording on the optical disk, the recording is performed in a state where the spot of the light beam spreads, and therefore there is a possibility that information cannot be recorded accurately.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an optical information processing apparatus and an optical information processing method in which the quality of a reproduction signal reproduced from an optical disc is good.

  In order to achieve the object, an optical information processing apparatus according to the present invention includes an optical head that irradiates light to an optical information recording medium, converts the light reflected by the optical information recording medium into a head signal, and outputs the head signal. A signal quality indicator detector for detecting a signal quality indicator representing the quality of the head signal based on the head signal output from the optical head; and a focus position and a spherical surface of the light applied to the optical information recording medium A two-dimensional searcher for searching for a focus position and a spherical aberration amount at which the value of the signal quality index detected by the signal quality index detector is optimal by changing the amount of aberration; The dimension explorer changes the focus position X at a predetermined spherical aberration amount Y1 when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y. Thus, the focus position X1 at which the value of the signal quality index is optimal is searched for, and the focus position X is changed at a predetermined spherical aberration amount Y2, thereby the focus position X2 at which the value of the signal quality index is optimal. And the focus position X and the point on the straight line Y = (Y2−Y1) / (X2−X1) × (X−X1) + Y1 connecting the point (X1, Y1) and the point (X2, Y2). By changing the spherical aberration amount Y, the focus position and the spherical aberration amount at which the value of the signal quality index is optimum are searched.

  In this specification, the signal quality index refers to an index representing the quality of the head signal converted by the optical head from the light reflected by the optical information recording medium. The signal quality index includes, for example, jitter, error rate, reproduction signal amplitude, tracking error signal amplitude, focus error signal amplitude, and wobble signal amplitude.

  An optical information processing method according to the present invention includes an optical head signal output step of irradiating an optical information recording medium with light, converting the light reflected by the optical information recording medium into a head signal and outputting the head signal, and the optical head A signal quality indicator detecting step for detecting a signal quality indicator representing the quality of the head signal based on the head signal output in the signal output step; and a focus position and spherical aberration of the light irradiated on the optical information recording medium A two-dimensional search step for searching for a focus position and a spherical aberration amount at which the value of the signal quality indicator detected by the signal quality indicator detection step is optimal by changing the amount, In the exploration step, when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y, the focus position X is changed at a predetermined spherical aberration amount Y1. Thus, the focus position X1 at which the value of the signal quality index is optimal is searched, and the focus position X is changed at a predetermined spherical aberration amount Y2, thereby the focus position at which the value of the signal quality index is optimal. X2 is searched, and the focus position X is on the straight line Y = (Y2−Y1) / (X2−X1) × (X−X1) + Y1 connecting the point (X1, Y1) and the point (X2, Y2). By changing the spherical aberration amount Y, the focus position and the spherical aberration amount at which the value of the signal quality index is optimum are searched.

  As described above, according to the present invention, it is possible to provide an optical information processing apparatus and an optical information processing method in which the quality of a reproduction signal reproduced from an optical disc is good.

  In the optical information processing apparatus according to the present embodiment, the value of the signal quality index detected by the signal quality index detector is changed by changing the focus position and the spherical aberration amount of the light irradiated to the optical information recording medium. The two-dimensional probe searches for the focus position and the spherical aberration amount that are optimal. For this reason, the value of the signal quality index can be optimized based not only on the focus position of the light applied to the optical information recording medium but also based on the amount of spherical aberration of the light applied to the optical information recording medium. As a result, an optical information processing apparatus that can optimize the quality of the head signal output from the optical head can be provided.

  The two-dimensional prober includes a focus position prober that searches for a focus position at which the value of the signal quality index is optimal by changing the focus position, and the signal quality by changing the amount of spherical aberration. It is preferable to have a spherical aberration amount searcher that searches for the spherical aberration amount that optimizes the index value.

  The two-dimensional searcher alternately repeats the search for the focus position by the focus position searcher and the search for the spherical aberration amount by the spherical aberration amount searcher, so that the value of the signal quality index becomes optimum. It is preferable to search the focus position and the spherical aberration amount.

  The two-dimensional probe defines the focus position as a variable X and the spherical aberration amount as a variable Y, and sets n values (n is an integer of 2 or more) within a range ΔX in the variable X to Xi (i is Each point (m is an integer of 1 or more and n or less) and m (m is an integer of 2 or more) within the range ΔY in the variable Y is Yj (j is an integer of 1 or more and m or less). By comparing the values of the signal quality index in Xi, Yj), the point (Xa, Yb) where the value of the signal quality index is optimal is searched, and the point (Xa , Yb), it is preferable to obtain the focus position and the spherical aberration amount at which the value of the signal quality index is optimal by repeating the search.

  When the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y, the two-dimensional probe searches for the value of the signal quality index by changing the focus position X at a predetermined spherical aberration amount Y1. Is searched for the optimum focus position X1, and by changing the focus position X in a predetermined spherical aberration amount Y2, the focus position X2 where the value of the signal quality index is optimum is searched, and the point (X1, Y1 ) And the point (X2, Y2), the focus position X and the spherical aberration amount Y are changed on a straight line Y = (Y2−Y1) / (X2−X1) × (X−X1) + Y1. Thus, it is preferable to search for the focus position and the spherical aberration amount at which the value of the signal quality index is optimal.

  When the focus position is defined as a variable X and the amount of spherical aberration is defined as a variable Y, the two-dimensional explorer changes the value of the signal quality index by changing the amount of spherical aberration Y at a predetermined focus position X1. Is searched for the spherical aberration amount Y1 at which the signal quality index is optimal, and the spherical aberration amount Y2 at which the value of the signal quality index is optimal is searched for by changing the spherical aberration amount Y at a predetermined focus position X2. , Y1) and the point (X2, Y2), the focus position X and the spherical aberration amount Y are changed on a straight line Y = (Y2-Y1) / (X2-X1) × (X-X1) + Y1. It is preferable to search for the focus position and the spherical aberration amount at which the value of the signal quality index is optimal.

  When the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y, the two-dimensional probe has the focus position X on a straight line Y = aX + Y0 having a slope a passing through a predetermined spherical aberration amount Y0. And the spherical aberration amount Y are searched for the focus position X1 and the spherical aberration amount Y1 at which the value of the signal quality index is optimal, and the inclination of −1 / a passing through the point (X1, Y1) is obtained. By changing the focus position X and the spherical aberration amount Y on the straight line Y = − (X−X1) / a + Y1, the focus position and the spherical aberration amount at which the value of the signal quality index is optimal are obtained. Exploration is preferred.

  Assuming that the wavelength of light irradiated to the optical information recording medium is λ and the numerical aperture is NA, the wavelength λ is 390 nanometers (nm) to 420 nanometers, and the numerical aperture NA is about 0.85. The value of the slope a is preferably 0.1λ rms / μm or more and 0.3λ rms / μm or less.

  Preferably, the signal quality indicator detected by the signal quality indicator detector is jitter, and the two-dimensional searcher searches for a focus position and a spherical aberration amount at which the jitter value is minimized.

  Preferably, the signal quality indicator detected by the signal quality indicator detector is an error rate, and the two-dimensional searcher searches for a focus position and a spherical aberration amount at which the error rate value is minimized. .

  The signal quality indicator detected by the signal quality indicator detector is an amplitude of a reproduction signal, and the two-dimensional searcher searches for a focus position and a spherical aberration amount at which the amplitude value of the reproduction signal is maximized. It is preferable to do.

  The signal quality indicator detected by the signal quality indicator detector is an amplitude of a tracking error signal, and the two-dimensional prober has a focus position and a spherical aberration amount at which the amplitude value of the tracking error signal is maximized. It is preferable to explore.

  The signal quality indicator detected by the signal quality indicator detector is an amplitude of a wobble signal, and the two-dimensional probe searches for a focus position and a spherical aberration amount at which the amplitude value of the wobble signal is maximized. It is preferable to do.

  Test information is recorded on the optical information recording medium, and the head signal converted from the light reflected by the optical information recording medium is obtained by reproducing the test information. Preferably it is a signal.

  The signal quality indicator includes a focus error signal and a tracking error signal, and the two-dimensional searcher searches for a focus position where the amplitude of the tracking error signal is maximized by changing the focus position. A focus position searcher; and a spherical aberration amount searcher that searches for a spherical aberration amount that maximizes the amplitude of the focus error signal by changing the spherical aberration amount, and the optical head includes the optical head, It is preferable to record the test information on the optical information recording medium at a spherical aberration amount at which the amplitude of the focus error signal is maximized and at a focus position at which the amplitude of the tracking error signal is maximized.

  In the optical information processing method according to the present embodiment, the value of the signal quality index detected by the signal quality index detection step by changing the focus position and the spherical aberration amount of the light irradiated to the optical information recording medium. The two-dimensional search process searches for a focus position and a spherical aberration amount that are optimal. For this reason, the value of the signal quality index can be optimized based not only on the focus position of the light applied to the optical information recording medium but also based on the amount of spherical aberration of the light applied to the optical information recording medium. As a result, it is possible to provide an optical information processing method capable of optimizing the quality of the head signal output from the optical head.

  The two-dimensional search step includes a focus position search step for searching for a focus position at which the value of the signal quality index is optimal by changing the focus position, and the signal quality by changing the amount of spherical aberration. It is preferable to include a spherical aberration amount search step for searching for a spherical aberration amount that optimizes the index value.

  In the two-dimensional search step, the value of the signal quality index is optimized by alternately repeating the focus position search in the focus position search step and the spherical aberration amount search in the spherical aberration amount search step. It is preferable to search the focus position and the spherical aberration amount.

  In the two-dimensional exploration step, the focus position is defined as a variable X, the spherical aberration amount is defined as a variable Y, and n values (n is an integer of 2 or more) within a range ΔX in the variable X are expressed as Xi (where i is Each point (m is an integer of 1 or more and n or less) and m (m is an integer of 2 or more) within the range ΔY in the variable Y is Yj (j is an integer of 1 or more and m or less). By comparing the values of the signal quality index in Xi, Yj), the point (Xa, Yb) where the value of the signal quality index is optimal is searched, and the point (Xa , Yb), it is preferable to obtain the focus position and the spherical aberration amount at which the value of the signal quality index is optimal by repeating the search.

  In the two-dimensional exploration step, when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y, the value of the signal quality index is changed by changing the focus position X at a predetermined spherical aberration amount Y1. Is searched for the optimum focus position X1, and by changing the focus position X in a predetermined spherical aberration amount Y2, the focus position X2 where the value of the signal quality index is optimum is searched, and the point (X1, Y1 ) And the point (X2, Y2), the focus position X and the spherical aberration amount Y are changed on a straight line Y = (Y2−Y1) / (X2−X1) × (X−X1) + Y1. Thus, it is preferable to search for the focus position and the spherical aberration amount at which the value of the signal quality index is optimal.

  In the two-dimensional search step, when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y, the value of the signal quality index is changed by changing the spherical aberration amount Y at a predetermined focus position X1. Is searched for the spherical aberration amount Y1 at which the signal quality index is optimal, and the spherical aberration amount Y2 at which the value of the signal quality index is optimal is searched for by changing the spherical aberration amount Y at a predetermined focus position X2. , Y1) and the point (X2, Y2), the focus position X and the spherical aberration amount Y are changed on a straight line Y = (Y2-Y1) / (X2-X1) × (X-X1) + Y1. It is preferable to search for the focus position and the spherical aberration amount at which the value of the signal quality index is optimal.

  In the two-dimensional search step, when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y, the focus position X is on a straight line Y = aX + Y0 having a slope a passing through a predetermined spherical aberration amount Y0. And the spherical aberration amount Y are searched for the focus position X1 and the spherical aberration amount Y1 at which the value of the signal quality index is optimal, and the inclination of −1 / a passing through the point (X1, Y1) is obtained. By changing the focus position X and the spherical aberration amount Y on the straight line Y = − (X−X1) / a + Y1, the focus position and the spherical aberration amount at which the value of the signal quality index is optimal are obtained. Exploration is preferred.

  Assuming that the wavelength of light irradiated to the optical information recording medium is λ and the numerical aperture is NA, the wavelength λ is 390 nanometers (nm) to 420 nanometers, and the numerical aperture NA is about 0.85. The value of the slope a is preferably 0.1λ rms / μm or more and 0.3λ rms / μm or less.

  Preferably, the signal quality index detected by the signal quality index detection step is jitter, and the two-dimensional search step searches for a focus position and a spherical aberration amount at which the jitter value is minimized.

  Preferably, the signal quality index detected by the signal quality index detection step is an error rate, and the two-dimensional search step searches for a focus position and a spherical aberration amount at which the error rate value is minimized. .

  The signal quality index detected by the signal quality index detection step is an amplitude of a reproduction signal, and the two-dimensional search step searches for a focus position and a spherical aberration amount at which the amplitude value of the reproduction signal is maximized. It is preferable to do.

  The signal quality index detected by the signal quality index detection step is an amplitude of a tracking error signal, and the two-dimensional search step includes a focus position and a spherical aberration amount at which the amplitude value of the tracking error signal is maximized. It is preferable to explore.

  The signal quality index detected by the signal quality index detection step is an amplitude of a wobble signal, and the two-dimensional search step searches for a focus position and a spherical aberration amount at which the amplitude value of the wobble signal is maximized. It is preferable to do.

  Test information is recorded on the optical information recording medium, and the head signal converted from the light reflected by the optical information recording medium is obtained by reproducing the test information. Preferably it is a signal.

  The signal quality index includes a focus error signal and a tracking error signal, and the two-dimensional search step searches for a focus position where the amplitude of the tracking error signal is maximized by changing the focus position. A focus position searching step; and a spherical aberration amount searching step for searching for a spherical aberration amount that maximizes the amplitude of the focus error signal by changing the spherical aberration amount, and the optical head signal output step. Preferably, the test information is recorded on the optical information recording medium at a spherical aberration amount at which the amplitude of the focus error signal is maximized and at a focus position at which the amplitude of the tracking error signal is maximized.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an optical information processing apparatus 100 according to the present embodiment. FIG. 2 is a block diagram for explaining a configuration of an optical head 5 provided in the optical information processing apparatus 100. FIG. 3 is a block diagram showing a configuration of the minimum jitter probe 1 provided in the optical information processing apparatus 100.

  The optical information processing apparatus 100 includes an optical head 5. The optical head 5 is provided with a semiconductor laser 23. The light beam 22 emitted from the semiconductor laser 23 passes through the prism 24, is collimated by the condenser lens 13, and becomes a substantially parallel light beam.

  The light beam collimated by the condenser lens 13 passes through the concave lens and the convex lens provided in the spherical aberration correction device 7 and is reflected by the mirror 14. The light beam reflected by the mirror 14 is converged by the objective lens 9, forms a spot on the recording surface formed on the optical disc 6, and is reflected by the recording surface. The reflected light 33 reflected by the recording surface again passes through the objective lens 9, is reflected by the mirror 14, passes through the spherical aberration correction device 7, and is narrowed down by the condenser lens 13. The reflected light 33 focused by the condenser lens 13 is reflected by the prism 24 and passes through the hologram 15 provided for detecting the amount of spherical aberration and the cylindrical lens 16 provided for detecting the focus position. , Enters the photodetector 17.

  The photodetector 17 generates a head signal based on the incident reflected light 33 and outputs the head signal to the preamplifier 18. The preamplifier 18 generates a focus error signal FE according to the astigmatism method based on the head signal output from the photodetector 17 provided in the optical head 5 and outputs the focus error signal FE to the adder 25. The preamplifier 18 also individually detects the focus error signal of the inner peripheral portion and the focus error signal of the outer peripheral portion of the reflected light 33, generates a spherical aberration amount error signal SAE based on the difference therebetween, and adds the adder 26. Output to. The preamplifier 18 further amplifies the head signal output from the optical head 5 to generate a reproduction signal RF and outputs it to the jitter detector 4. The jitter detector 4 measures the jitter of the reproduction signal RF output from the preamplifier 18 and outputs the result to the minimum jitter prober 1 as a jitter detection signal JT.

  Here, jitter refers to 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. Therefore, jitter is used as an evaluation value for control in the optical information processing apparatus.

  The minimum jitter prober 1 has a focus position prober 2. The focus position searcher 11 generates a focus position compensation signal ΔFE and outputs the focus position compensation signal ΔFE to the adder 25 in order to search for a focus position at which the value of the jitter detection signal JT is minimized by changing the focus position.

  The minimum jitter probe 1 is provided with a spherical aberration probe 3. The spherical aberration amount searcher 3 generates a spherical aberration amount compensation signal ΔSAE and outputs it to the adder 26 in order to search for the spherical aberration amount that minimizes the value of the jitter detection signal JT by changing the spherical aberration amount. .

  The adder 25 adds the focus error signal FE output from the preamplifier 18 and the focus position compensation signal ΔFE output from the focus position searcher 11 provided in the minimum jitter searcher 1, and the result is focused. Output to the controller 11. The focus controller 11 outputs a control signal to the focus actuator 10 provided in the optical head 5 based on the addition result output from the adder 25. The focus actuator 10 drives the objective lens 9 along the direction perpendicular to the optical disk 6 so as to control the focus position of the light beam that converges on the optical disk 6 based on the control signal output from the focus controller 11. . In this way, focus control is executed.

  The adder 26 adds the spherical aberration amount error signal SAE output from the preamplifier 18 and the spherical aberration amount compensation signal ΔSAE output from the spherical aberration amount searcher 3, and sends the result to the spherical aberration amount controller 12. Output. Based on the addition result output from the adder 26, the spherical aberration amount controller 12 outputs a control signal to the spherical aberration amount correction actuator 8 provided in the spherical aberration amount correction device 7 of the optical head 5. The spherical aberration amount correcting actuator 8 is a spherical surface in order to correct the spherical aberration amount caused by the thickness error of the protective layer formed on the optical disc 6 based on the control signal output from the spherical aberration amount controller 12. The degree of divergence of the light beam is changed by changing the distance between the two lenses provided in the aberration correction device 7.

  FIG. 4 is a graph showing the jitter characteristics with respect to the focus position and the spherical aberration amount in the optical information processing apparatus 100. The horizontal axis indicates the focus position of the light beam applied to the optical disk 6 by the optical head 5, and the vertical axis indicates the spherical aberration amount of the light beam on the recording surface formed on the optical disk 6. The value of jitter is shown by a contour map composed of a plurality of ellipses drawn concentrically. The jitter values are equal on the outer circumference of each ellipse, and the jitter values become smaller as the ellipse approaches the center of each ellipse. Therefore, the jitter value is minimized at the center of each ellipse.

  As shown in FIG. 4, the major and minor axes of each ellipse are inclined with respect to the horizontal and vertical axes. This means that the focus position and the spherical aberration amount are influenced by each other with respect to jitter. Therefore, in order to minimize the jitter, it is not desirable to adjust the focus position and the spherical aberration amount independently of each other, and it is necessary to adjust them while associating them. That is, in order to minimize the jitter value, it is necessary to search two-dimensionally in consideration of both the focus position and the spherical aberration amount.

  The minimum jitter probe 1 performs such a two-dimensional search. For example, in the optical information processing apparatus 100 according to the present embodiment, the minimum jitter probe 1 is constituted by a microprocessor. If the minimum jitter prober 1 is constituted by a microprocessor, the two-dimensional search can be easily realized by programming even if the two-dimensional search method is somewhat complicated.

  FIG. 5 is a graph for explaining the two-dimensional exploration by the optical information processing apparatus 100. Similar to FIG. 4 described above, the horizontal axis indicates the focus position of the light beam, and the vertical axis indicates the amount of spherical aberration. The value of jitter is shown by a contour map composed of a plurality of ellipses drawn concentrically. Hereinafter, for the sake of brevity, the focus position is X and the spherical aberration amount is Y.

First, the focus position searcher 11 provided in the minimum jitter searcher 1 changes the focus position X on a straight line with a predetermined spherical aberration amount Y = Y ₁ to change the focus value X _{1 at} which the jitter value becomes minimum. Exploring. Then, the spherical aberration amount searcher 3 searches for the spherical aberration amount Y ₂ that minimizes the jitter value by changing the spherical aberration amount Y on the straight line of the focus position X = X ₁ . The search for the focus position X by the focus position searcher 11 and the search for the spherical aberration amount Y by the spherical aberration amount searcher 3 are alternately repeated to indicate the zigzag-shaped broken line drawn in FIG. In this way, the jitter value is reduced, and the jitter value does not decrease any more by both the search of the focus position X by the focus position searcher 11 and the search of the spherical aberration amount Y by the spherical aberration searcher 3. The exploration is repeated when the hit state is reached. In this way, it is possible to obtain the focus position and the spherical aberration amount that minimize the jitter value.

  FIG. 6 is a flowchart showing an operation for two-dimensional exploration by the optical information processing apparatus 100. First, in step S1, initial values of the focus position X and the spherical aberration amount Y are set. As the initial value, a value set in advance with a jitter small enough to reproduce the signal is used by experiment, simulation, or the like. In step S2, the focus position searcher 11 changes the focus position X by ΔX. Thereafter, the jitter detector 4 measures the jitter. Next, in step S3, the focus position searcher 11 determines whether or not the measured jitter value is minimized. The process returns to step S2 until the jitter value is minimized, and the focus position searcher 11 changes the focus position X. If the jitter is minimized (YES in step S3), the process proceeds to step S4.

  In step S4, the spherical aberration probe 3 changes the spherical aberration amount Y by ΔY. Then, the jitter detector 4 measures jitter. Thereafter, in step S5, the spherical aberration detector 3 determines whether or not the measured jitter value is minimized. The process returns to step S4 until the jitter value is minimized, and the spherical aberration amount searcher 3 changes the spherical aberration amount Y. If the jitter is minimized (YES in step S5), the process proceeds to step S6.

  In step S6, the minimum jitter prober 1 determines whether or not the minimum jitter value has converged, and steps S2 to S5 are repeated until it converges. As a convergence determination condition for determining whether or not the minimum jitter value has converged, the change in the minimum jitter value may be equal to or less than a preset value. When the jitter minimum value has converged (YES in step S6), the two-dimensional search ends.

  As described above, according to the present embodiment, the focus position at which the jitter value detected by the jitter detector 4 is minimized by changing the focus position of the light beam applied to the optical disc 6 and the amount of spherical aberration. The minimum jitter prober 1 searches for the spherical aberration amount. For this reason, the value of jitter can be optimized based not only on the focus position of the light beam applied to the optical disc 6 but also on the amount of spherical aberration of the light beam applied to the optical disc 6. As a result, it is possible to provide an optical information processing apparatus capable of optimizing the quality of a reproduction signal reproduced based on the head signal output from the optical head 5.

  In the present embodiment, an example in which the signal quality index is jitter in the focus position search by the focus position searcher 11 and the spherical aberration search by the spherical aberration searcher 3 has been shown. It is not limited to. The signal quality index is the amplitude of a wobble signal obtained by scanning a light spot on an information track wobbled with an error rate, reproduction signal amplitude, tracking error signal amplitude, focus error signal amplitude, and a predetermined frequency. May be. The same applies to the embodiments described later.

  The jitter, error rate, and reproduction signal can be obtained by reproducing a track in which disk information, address, and data are recorded with an optical head. In the case of an unrecorded optical disc, the test information generated by the recording signal generator 22 (FIG. 1), which is a recording signal generator, is recorded on the optical disc 6 by the optical head 5, and the recorded test information is recorded. Jitter, error rate and reproduction signal can be obtained.

  At this time, experimental information is recorded at the spherical aberration amount at which the amplitude of the focus error signal is maximized in the spherical aberration amount searcher 3 and at the focus position at which the amplitude of the tracking error signal is maximized in the focus position searcher 11. For example, it is possible to record with a more narrow spot. The recorded experimental information may be deleted after the search for the focus position and the spherical aberration amount at which the value of the signal quality index is optimum is completed. Alternatively, a test track may be provided on the optical disc 6 and test information may be recorded on the test track.

  FIG. 7 is a graph for explaining another two-dimensional exploration by the optical information processing apparatus 100. Similar to FIG. 5 described above, the horizontal axis indicates the focus position of the light beam, and the vertical axis indicates the amount of spherical aberration. The value of jitter is shown by a contour map composed of a plurality of ellipses drawn concentrically.

First, the minimum jitter prober 1 searches for a point having the smallest jitter value among the five points A ₀ , A ₁ , A ₂ , A ₃ and A _{4 shown} in FIG. The points A ₁ , A ₂ , A _3, and A ₄ form rectangular vertices having a side length of ΔX along the X-axis direction and a side length of ΔY along the Y-axis direction, respectively. is doing. Point A ₀ is located at the center of the rectangle formed by points A ₁ , A ₂ , A ₃ and A ₄ . In the contour map shown in FIG. 7, the point at which the value of the jitter probed by the minimum jitter probe 1 is the minimum is the point A ₀ .

Next, the minimum jitter prober 1 searches for a point having the smallest jitter value among the five points A ₀ , B ₁ , B ₂ , B ₃ and B ₄ . B ₁ , B ₂ , B _3, and B ₄ form a rectangular vertex centered at the point A ₀ , respectively. In the rectangle formed by the points B ₁ , B ₂ , B ₃ and B ₄ , the length of one side along the X-axis direction is shorter than ΔX, and the length of one side along the Y-axis direction is ΔY Is shorter. In the contour map shown in FIG. 7, the point where the value of the jitter probed by the minimum jitter probe 1 is minimum is the point B ₃ .

Then, when the above-described search is repeated with the ΔX and ΔY being made smaller around the point B ₃ where the jitter found by this search is minimized, the jitter value decreases. When the jitter value reaches a bottoming state where the jitter value does not decrease any more, the search is repeated repeatedly. In this way, it is possible to obtain the focus position and the spherical aberration amount that minimize the jitter value. This search method can reduce the number of jitter measurement points as compared with the search method described above with reference to FIG. Therefore, it is possible to search faster than the search method described above with reference to FIG.

  FIG. 8 is a flowchart showing an operation for another two-dimensional exploration by the optical information processing apparatus 100. First, in step S11, the minimum jitter prober 1 sets initial values of the focus position X and the spherical aberration amount Y. As the initial value, a value set in advance with a jitter small enough to reproduce the signal is used by experiment, simulation, or the like. In step S12, the minimum jitter probe 1 sets five measurement points included in the range of ΔX and ΔY with the initial value (X, Y) as the center. Next, in step S13, the jitter detector 4 measures the jitter values at the five measurement points, and the minimum jitter prober 1 searches for the measurement point at which the jitter is minimum among the five measurement points.

  Thereafter, in step S14, the minimum jitter prober 1 determines whether or not the minimum jitter value has converged. The convergence determination condition may be set such that when the change in the minimum jitter value is equal to or less than a preset value, the jitter measurement values at the five measurement points are the same.

  When it is determined that the minimum jitter value has not converged (NO in step S14), the values of ΔX and ΔY are further reduced, and steps S12 and S13 are repeated. When it is determined that the minimum jitter value has converged (YES in step S14), the two-dimensional search is terminated. As described above, it is possible to perform the focus control and the spherical aberration control with high accuracy by executing the two-dimensional search for obtaining the focus position and the spherical aberration amount that minimize the jitter.

  In the present embodiment, an example in which five jitter measurement points are included in the range of ΔX and ΔY has been described, but the present invention is not limited to this. The number of jitter measurement points may be 2 or more and 4 or less, or 6 or more.

  As described above, according to the present embodiment, the minimum jitter prober 1 defines the focus position as the variable X and the spherical aberration amount as the variable Y, and n (n is 2 or more) within the range ΔX in the variable X. An integer) value is Xi (i is an integer of 1 to n), and m values (m is an integer of 2 or more) within a range ΔY in the variable Y are Yj (j is an integer of 1 to m). Then, by comparing the jitter values at the respective points (Xi, Yj), the point (Xa, Yb) at which the jitter value is minimized is searched and the points ΔX and ΔY are reduced while decreasing the range ΔX and the range ΔY. Repeat the search around (Xa, Yb). For this reason, it is possible to accurately obtain the focus position and the spherical aberration amount that minimize the jitter value.

  FIG. 9 is a graph for explaining still another two-dimensional exploration by the optical information processing apparatus 100. Similar to FIG. 7 described above, the horizontal axis indicates the focus position of the light beam, and the vertical axis indicates the amount of spherical aberration. The value of jitter is shown by a contour map composed of a plurality of ellipses drawn concentrically.

First, the minimum jitter prober 1 searches the focus position X ₁ at which the jitter value is minimized by changing the focus position X on a predetermined spherical aberration amount Y = Y ₁ straight line. Next, the minimum jitter probe 1 searches the focus position X ₂ where the jitter value is minimized by changing the focus position X on another predetermined spherical aberration amount Y = Y ₂ straight line.

Then, the minimum jitter prober 1 has a straight line Y = (Y ₂ −Y ₁ ) / (X ₂ −X ₁ ) × (X connecting the point (X ₁ , Y ₁ ) and the point (X ₂ , Y ₂ ). The focus position and the spherical aberration amount at which the jitter value is minimized are searched by changing the focus position X and the spherical aberration amount Y on the straight line of −X ₁ ) + Y ₁ . This search method can further reduce the number of jitter measurement points as compared with the search method described above with reference to FIG. Therefore, it is possible to search faster than the search method described above with reference to FIG.

FIG. 10 is a flowchart showing an operation for still another two-dimensional exploration by the optical information processing apparatus 100. First, in step S31, initial values of the focus position X and the spherical aberration amounts Y ₁ and Y ₂ are set. As the initial value, a value set in advance with a jitter small enough to reproduce the signal is used by experiment, simulation, or the like. In step S32, jitter is measured by changing the focus position X by ΔX on the straight line of the spherical aberration amount Y ₁ . Next, in step S33, it is determined whether or not the measured jitter value is minimum. If it is determined that the measured jitter value is not the minimum (NO in step S33), the process returns to step S32 and the focus position X is changed until the jitter value becomes the minimum. When it is determined that the measured jitter value is minimum (YES in step S33), the process proceeds to step S34.

Then, in step S34, the straight line of the spherical aberration Y _2, the focal position X is varied by ΔX to measure the jitter. Next, in step S35, it is determined whether or not the measured jitter value is minimum. When it is determined that the measured jitter value is not the minimum (NO in step S35), the process returns to step S34 and the focus position X is changed until the jitter value becomes the minimum. When it is determined that the measured jitter value is minimum (YES in step S35), the process proceeds to step S36.

Thereafter, in step S36, the focus position X is changed by ΔX, and the spherical aberration amount Y is an expression Y = (Y ₂ ) representing a straight line connecting the point (X ₁ , Y ₁ ) and the point (X ₂ , Y ₂ ). as _{-Y 1) / (X 2 -X} 1) × (X-X 1) + value obtained Y ₁ by substituting X, to measure the jitter. In step S37, it is determined whether or not the measured jitter value is minimized. If it is determined that the measured jitter value is not minimum (NO in step S37), the process returns to step S36 to change the focus position X and the spherical aberration amount Y until the jitter value becomes minimum. When it is determined that the measured jitter value is minimum (YES in step S37), the two-dimensional search is terminated.

  As described above, according to the present embodiment, the minimum jitter prober 1 changes the focus position X at the predetermined spherical aberration amount Y1 when the focus position is defined as the variable X and the spherical aberration amount is defined as the variable Y. Thus, the focus position X1 at which the jitter value is minimized is searched, and the focus position X2 at which the jitter value is minimized is searched by changing the focus position X at a predetermined spherical aberration amount Y2. , Y1) and the point (X2, Y2), the focus position X and the spherical aberration amount Y are changed on a straight line Y = (Y2−Y1) / (X2−X1) × (X−X1) + Y1. Thus, the focus position and the spherical aberration amount that minimize the jitter value are searched. For this reason, the focus position and the spherical aberration amount that minimize the jitter value can be obtained with high accuracy and at high speed.

The focus position X was searched under the predetermined spherical aberration amounts Y = Y ₁ and Y = Y ₂ , but the spherical aberration amount under the predetermined focus positions X = X ₁ and X = X _2. It goes without saying that a search similar to that described above may be performed by searching for Y.

FIG. 11 is a graph for explaining still another two-dimensional exploration by the optical information processing apparatus 100. First, the minimum jitter prober 1 changes the focus position X and the spherical aberration amount Y on the straight line Y = aX + Y _{0 having} a slope a passing through the predetermined spherical aberration amount Y ₀ to minimize the jitter value. The focus position X ₁ and the spherical aberration amount Y ₁ are searched. Next, the minimum jitter prober 1 has a focus position X and a spherical aberration amount on a straight line Y = − (X−X ₁ ) / a + Y ₁ with a slope −1 / a passing through the point (X ₁ , Y ₁ ). The focus position and the spherical aberration amount at which the jitter value is minimized are searched by changing Y.

  The inclination a is determined according to the numerical aperture, wavelength, and recording method. When the slope a is set to a value of 0.1λ rms / μm or more and 0.3λ rms / μm or less (λ is the wavelength of light), it has a numerical aperture NA of 0.85, and light with a wavelength of 390 nanometers to 420 nanometers This is effective when an optical head for irradiating an optical disk is used.

  This exploration method utilizes the fact that the major axis and minor axis of each ellipse constituting the contour map representing the jitter characteristics have a certain inclination with respect to the X axis and the Y axis, respectively. The number of jitter measurement points can be further reduced as compared with the search method described above with reference to FIG. Therefore, it is possible to search faster than the search method described above with reference to FIG.

FIG. 12 is a flowchart showing still another operation for two-dimensional exploration by the optical information processing apparatus 100. First, in step S41, initial values of the inclination a and the spherical aberration amount Y ₀ are set. As the initial value, a value set in advance with a jitter small enough to reproduce the signal is used by experiment, simulation, or the like. Then, in step S42, the focus position X is varied by [Delta] X, the spherical aberration Y is a value obtained by substituting X into equation Y = aX + Y _0, to measure the jitter.

  Next, in step S43, it is determined whether or not the measured jitter value is minimum. If it is determined that the measured jitter value is not minimum (NO in step S43), the process returns to step S42 to change the focus position X and the spherical aberration amount Y until the jitter value becomes minimum. When it is determined that the measured jitter value is minimized (YES in step S43), the process proceeds to step S44.

In step S44, the focus position X is changed by ΔX, and the spherical aberration amount Y is set to a value obtained by substituting X into the equation Y = − (X−X ₁ ) / a + Y ₁ , and jitter is measured. Next, in step S45, it is determined whether or not the measured jitter value is minimized. If it is determined that the measured jitter value is not minimized (NO in step S45), the process returns to step S44 and the focus position X and the spherical aberration amount Y are changed until the jitter value is minimized. When it is determined that the measured jitter value is minimized (YES in step S45), the two-dimensional search is terminated.

  As described above, according to the present embodiment, when the focus position is defined as the variable X and the spherical aberration amount is defined as the variable Y, the minimum jitter prober 1 has the straight line Y with the inclination a passing through the predetermined spherical aberration amount Y0. By changing the focus position X and the spherical aberration amount Y on the straight line of = aX + Y0, the focus position X1 and the spherical aberration amount Y1 at which the jitter value is optimum are searched, and the inclination passes through the point (X1, Y1). By changing the focus position X and the spherical aberration amount Y on the straight line Y =-(X−X1) / a + Y1, the focus position and the spherical aberration amount at which the jitter value is minimized are obtained. Explore. For this reason, the focus position and the spherical aberration amount that minimize the jitter value can be obtained with high accuracy and at high speed.

  In the above-described embodiment, the example in which the spherical aberration amount is corrected by changing the distance between the two lenses provided in the spherical aberration correction device 7 of the optical head 5 has been described. The invention is not limited to this. The amount of spherical aberration may be corrected by a liquid crystal element.

  FIG. 13 is a block diagram for explaining the configuration of another optical head 5A provided in the optical information processing apparatus 100 according to the present embodiment, and FIG. 14 is a liquid crystal element 31 provided in the other optical head 5A. FIG. The same components as those of the optical head 5 described above with reference to FIG. 2 are denoted by the same reference numerals. Therefore, detailed description of these components is omitted. The difference from the optical head 5 described above is that a liquid crystal element 31 is provided instead of the spherical aberration correction device 7. As shown in FIG. 14, the electrodes provided in the liquid crystal element 31 are divided into a plurality of regions by a plurality of concentric circles. The amount of spherical aberration can be corrected by adjusting the voltage applied to each electrode provided in each region and adjusting the phase difference of light transmitted through the liquid crystal element 31.

It is a block diagram which shows the structure of the optical information processing apparatus which concerns on this Embodiment. It is a block diagram for demonstrating the structure of the optical head provided in the optical information processing apparatus which concerns on this Embodiment. It is a block diagram which shows the structure of the minimum jitter probe provided in the optical information processing apparatus which concerns on this Embodiment. It is a graph which shows the characteristic of the jitter with respect to the focus position and spherical aberration amount in the optical information processing apparatus according to the present embodiment. It is a graph for demonstrating the two-dimensional search by the optical information processing apparatus which concerns on this Embodiment. It is a flowchart which shows the operation | movement for the two-dimensional search by the optical information processing apparatus which concerns on this Embodiment. It is a graph for demonstrating the other two-dimensional search by the optical information processing apparatus which concerns on this Embodiment. It is a flowchart which shows the operation | movement for the other two-dimensional search by the optical information processing apparatus which concerns on this Embodiment. It is a graph for demonstrating other two-dimensional search by the optical information processing apparatus which concerns on this Embodiment. It is a flowchart which shows the operation | movement for the other two-dimensional search by the optical information processing apparatus which concerns on this Embodiment. It is a graph for demonstrating other two-dimensional search by the optical information processing apparatus which concerns on this Embodiment. It is a flowchart which shows the operation | movement for the other two-dimensional search by the optical information processing apparatus which concerns on this Embodiment. It is a block diagram for demonstrating the structure of the other optical head provided in the optical information processing apparatus which concerns on this Embodiment. It is a front view of the liquid crystal element provided in the other optical head concerning this Embodiment. It is a block diagram which shows the structure of the conventional optical information processing apparatus. It is a block diagram for demonstrating the structure of the optical head provided in the conventional optical information processing apparatus. (A)-(c) is a graph which shows the relationship between a wavefront aberration and the distance from the center of a light beam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Minimum jitter probe 2 Focus position probe 3 Spherical aberration probe 4 Jitter detector 5 Optical head 6 Optical disk 7 Spherical aberration corrector 8 Spherical aberration corrector actuator 9 Objective lens 10 Focus actuator 11 Focus controller 12 Spherical aberration Quantity controller 13 Condenser lens 14 Mirror 15 Hologram 16 Cylindrical lens 17 Photo detector 18 Preamplifiers 25 and 26 Adder

Claims (18)

An optical head that irradiates light onto an optical information recording medium, converts the light reflected by the optical information recording medium into a head signal, and outputs the head signal;
A signal quality indicator detector for detecting a signal quality indicator representing the quality of the head signal based on the head signal output from the optical head;
The focus position and spherical aberration at which the value of the signal quality index detected by the signal quality index detector is optimized by changing the focus position and spherical aberration amount of the light irradiated onto the optical information recording medium A two-dimensional probe for exploring quantities,
When the two-dimensional probe defines the focus position as a variable X and the spherical aberration amount as a variable Y,
By changing the focus position X at a predetermined spherical aberration amount Y1, the focus position X1 where the value of the signal quality index is optimal is searched,
By changing the focus position X at a predetermined spherical aberration amount Y2, the focus position X2 where the value of the signal quality index is optimal is searched,
On the straight line Y = (Y2-Y1) / (X2-X1) × (X−X1) + Y1 connecting the point (X1, Y1) and the point (X2, Y2), the focus position X and the spherical aberration amount Y The optical information processing apparatus searches for a focus position and a spherical aberration amount at which the value of the signal quality index is optimal. The two-dimensional searcher searches for a focus position where the value of the signal quality index is optimal by changing the focus position;
The optical information processing apparatus according to claim 1, further comprising a spherical aberration amount searcher that searches for a spherical aberration amount that optimizes the value of the signal quality index by changing the spherical aberration amount. The signal quality indicator detected by the signal quality indicator detector is jitter;
The optical information processing apparatus according to claim 1, wherein the two-dimensional probe searches for a focus position and a spherical aberration amount at which the jitter value is minimized. The signal quality indicator detected by the signal quality indicator detector is an error rate;
The optical information processing apparatus according to claim 1, wherein the two-dimensional probe searches for a focus position and a spherical aberration amount at which the error rate value is minimized. The signal quality indicator detected by the signal quality indicator detector is the amplitude of the reproduced signal;
The optical information processing apparatus according to claim 1, wherein the two-dimensional probe searches for a focus position and a spherical aberration amount at which the amplitude value of the reproduction signal is maximized. The signal quality indicator detected by the signal quality indicator detector is an amplitude of a tracking error signal;
The optical information processing apparatus according to claim 1, wherein the two-dimensional probe searches for a focus position and a spherical aberration amount at which the amplitude value of the tracking error signal is maximized. The signal quality indicator detected by the signal quality indicator detector is an amplitude of a wobble signal;
The optical information processing apparatus according to claim 1, wherein the two-dimensional probe searches for a focus position and a spherical aberration amount at which the amplitude value of the wobble signal is maximized. The optical head records test information by irradiating the optical information recording medium with light,
The optical information processing apparatus according to claim 1, wherein the head signal converted from the light reflected by the optical information recording medium is a signal obtained by reproducing the experimental information. The signal quality indicator includes a focus error signal and a tracking error signal,
The two-dimensional explorer includes a focus position searcher that searches for a focus position where the amplitude of the tracking error signal is maximized by changing the focus position;
A spherical aberration amount searcher for searching for a spherical aberration amount that maximizes the amplitude of the focus error signal by changing the spherical aberration amount;
The optical head records the test information on the optical information recording medium at a spherical aberration amount at which the amplitude of the focus error signal is maximized and a focus position at which the amplitude of the tracking error signal is maximized. 9. The optical information processing apparatus according to 8. An optical head signal output step of irradiating the optical information recording medium with light, converting the light reflected by the optical information recording medium into a head signal, and outputting the head signal;
A signal quality indicator detection step of detecting a signal quality indicator representing the quality of the head signal based on the head signal output in the optical head signal output step;
The focus position and spherical aberration at which the value of the signal quality index detected by the signal quality index detection step is optimized by changing the focus position and spherical aberration amount of the light irradiated onto the optical information recording medium Including a two-dimensional exploration process for exploring quantities,
In the two-dimensional exploration step, when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y,
By changing the focus position X at a predetermined spherical aberration amount Y1, the focus position X1 where the value of the signal quality index is optimal is searched,
By changing the focus position X at a predetermined spherical aberration amount Y2, the focus position X2 where the value of the signal quality index is optimal is searched,
On the straight line Y = (Y2-Y1) / (X2-X1) × (X−X1) + Y1 connecting the point (X1, Y1) and the point (X2, Y2), the focus position X and the spherical aberration amount Y The optical information processing method is characterized in that the focus position and the spherical aberration amount at which the value of the signal quality index is optimal are searched for by changing. The two-dimensional exploration step includes a focus position exploration step of exploring a focus position at which the value of the signal quality index is optimal by changing the focus position;
The optical information processing method according to claim 10, further comprising: a spherical aberration amount searching step of searching for a spherical aberration amount that optimizes the value of the signal quality index by changing the spherical aberration amount. The signal quality indicator detected by the signal quality indicator detection step is jitter;
The optical information processing method according to claim 10, wherein the two-dimensional search step searches for a focus position and a spherical aberration amount at which the jitter value is minimized. The signal quality indicator detected by the signal quality indicator detection step is an error rate;
The optical information processing method according to claim 10, wherein the two-dimensional search step searches for a focus position and a spherical aberration amount at which the error rate value is minimized. The signal quality index detected by the signal quality index detection step is an amplitude of a reproduction signal,
The optical information processing method according to claim 10, wherein the two-dimensional search step searches for a focus position and a spherical aberration amount at which the amplitude value of the reproduction signal is maximized. The signal quality indicator detected by the signal quality indicator detection step is an amplitude of a tracking error signal;
The optical information processing method according to claim 10, wherein the two-dimensional search step searches for a focus position and a spherical aberration amount at which the amplitude value of the tracking error signal is maximized. The signal quality indicator detected by the signal quality indicator detection step is an amplitude of a wobble signal;
The optical information processing method according to claim 10, wherein the two-dimensional search step searches for a focus position and a spherical aberration amount at which the amplitude value of the wobble signal is maximized. Test information is recorded on the optical information recording medium,
The optical information processing method according to claim 10, wherein the head signal converted from the light reflected by the optical information recording medium is a signal obtained by reproducing the experimental information. The signal quality indicator includes a focus error signal and a tracking error signal,
The two-dimensional search step includes a focus position search step of searching for a focus position where the amplitude of the tracking error signal is maximized by changing the focus position;
A spherical aberration amount search step of searching for a spherical aberration amount that maximizes the amplitude of the focus error signal by changing the spherical aberration amount;
Prior to the optical head signal output step, the trial information is transferred to the optical information recording medium at the spherical aberration amount at which the amplitude of the focus error signal is maximized and the focus position at which the amplitude of the tracking error signal is maximized. The optical information processing method according to claim 17, further comprising an optical head recording step of recording.

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