JP2003233917A - Optical information processor and method for optical information processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information processor and a method for optical information processing which are excellent in the quality of a signal reproduced from an optical disk. <P>SOLUTION: The optical information processor comprises an optical head which irradiates an optical information recording medium with light, converts the light reflected by the optical information recording medium into a head signal, and outputs it, a signal quality index detector which detects a signal quality index representing the quality of the head signal according to the head signal outputted from the optical head, and a two-dimensional probe which probes a focus position where the value of the signal quality index detected by the signal quality index detector becomes optimum and a spherical aberration quantity by varying the focus position of the light irradiating the optical information recording medium and the spherical aberration quantity. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information processing apparatus and an optical information processing apparatus provided with an optical head which irradiates an optical information recording medium with light and converts the light reflected by the optical information recording medium into a head signal for output. Information processing method.

[0002]

2. Description of the Related Art DVD (Digital Versat)
An optical disc called "ile Disk" has a high density,
It is commercially available as a large capacity optical information recording medium. Such optical discs have recently become rapidly popular as recording media for recording images, music and computer data.
In recent years, research on next-generation optical discs with even higher recording densities has been underway in various places. Next-generation optical discs are currently the mainstream VTR (Video Tape Record).
er) is expected as a recording medium to replace the video tape, and is being developed at a rapid pace.

As a means for increasing the recording density of an optical disk, there is a method of reducing the spot formed on the recording surface formed on the optical disk. By increasing the numerical aperture of the light emitted from the optical head and shortening the wavelength of the emitted 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 is drastically increased. Increase to. Therefore, it is essential to provide a means for correcting the spherical aberration amount. Hereinafter, a conventional optical information processing device provided with a means for correcting the amount of spherical aberration will be described.

FIG. 15 is a block diagram showing the structure of a conventional optical information processing device 90, and FIG. 16 is a block diagram for explaining the structure of an optical head 5 provided in the conventional optical information processing device 90. . The optical information processing device 90 includes the optical head 5
Is equipped with. 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 the condenser lens 1
The light beams are collimated by 3 and become a substantially parallel light beam.

The light beam collimated by the condenser lens 13 passes through a concave lens and a convex lens provided in the spherical aberration correction device 7, and is reflected by a 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 passes through the objective lens 9 again, is reflected by the mirror 14, passes through the spherical aberration correction device 7, and is focused by the condenser lens 13. Reflected light 33 focused by the condenser lens 13
Is reflected by the prism 124, passes through the hologram 115 provided for detecting the amount of spherical aberration and the cylindrical lens 116 provided for detecting the focus position, and enters the photodetector 117.

The photodetector 117 generates a head signal based on the incident reflected light 33 and outputs it to the preamplifier 18. The preamplifier 18 generates and outputs the 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 Japanese Patent Publication No. 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 the 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 the detection signal FE.
Output to the maximum amplitude searcher 21 as _PP . The maximum amplitude searcher 21 outputs the spherical aberration amount compensation signal ΔSAE to the adder 26 so that the detection signal FE _PP has the maximum amplitude.

The maximum amplitude searcher 21 uses the detection signal FE _PP as an evaluation value to search the spherical aberration amount so that the detection signal FE _PP becomes maximum. As a method of searching such an optimum spherical aberration amount, for example, the spherical aberration amount compensation signal Δ
The SAE is slightly changed to slightly increase or decrease the spherical aberration amount, the increase or decrease in the amplitude of the detection signal FE _PP at that time is examined, and the spherical aberration amount compensation signal ΔS increases in the direction in which the detection signal FE _PP increases.
A method of changing AE 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 probe 21 to the spherical aberration amount controller 12.
Output to. The spherical aberration amount controller 12 changes the distance between the two lenses provided in the spherical aberration amount correction device 7 of the optical head 5 to change the degree of divergence of the light flux, and the thickness error of the protective layer formed on the optical disc 6. In order to correct the spherical aberration amount caused by the above, the spherical aberration amount correction actuator provided in the spherical aberration amount correction device 7 of the optical head 5 based on the spherical aberration amount compensation signal ΔSAE output from the adder 26. The control signal is output to 8.

The preamplifier 18 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 measuring device 4 measures the jitter of the reproduction signal RF output from the preamplifier 18,
The result is output to the minimum jitter detector 91 as a jitter detection signal JT.

Here, the jitter is a physical quantity representing a time shift of information transition in a reproduced signal. Jitter is closely related to the error rate, which indicates the probability that an error will occur when reading information from an optical disc. Therefore, the jitter is used as an evaluation value of control in the optical information processing device.

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, and outputs the focus position compensation signal ΔFE to the adder 25. The switch 28 is switched 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 probe 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 disc 6 so as to control the focus position of the light flux that converges on the optical disc 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 the off state to the on state. The maximum amplitude searcher 21 outputs to the adder 26 the spherical aberration amount 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 exploring device 21, and outputs the result to the spherical aberration amount controller 12. Output. 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 based on the addition result output from the adder 26. The spherical aberration correction actuator 8 corrects the spherical aberration generated due to the thickness error of the protective layer formed on the optical disc 6 based on the control signal output from the spherical aberration controller 12. The degree of divergence of the light flux is changed by changing the distance between the two lenses provided in the aberration correction device 7.

In the conventional optical disk device, the spherical aberration amount is first corrected in this way, and then the focus position where the jitter value is minimum is searched.

[0016]

[Patent Document 1] Japanese Patent Laid-Open No. 2001-507463

[0017]

However, in the conventional optical information processing apparatus configured as described above, the jitter may not necessarily converge to the minimum value.
It was revealed by the recent studies by the present inventors.

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 represents the distance from the center of the light beam that the optical head 5 irradiates the optical disk 6, and the vertical axis represents the wavefront aberration. Since the wavefront aberration is closely related to the jitter, it is used to evaluate the optical performance of the optical head.

FIG. 17 (a) shows the distance from the center of the light beam and the wavefront when the focus position of the light beam is located at a position slightly displaced from the recording surface formed on the optical disk along the direction perpendicular to the surface of the optical disk. The relationship between aberrations is shown. As shown in FIG. 17A, the curve showing the relationship between the distance from the center of the light beam and the wavefront aberration when the focus position of the light beam deviates from the recording surface is a quadratic curve.

FIG. 17B shows the distance from the center of the light flux when the spherical aberration correction device 7 gives a spherical aberration of 20 mλ when the focus position deviates from the recording surface as shown in FIG. 17A. And the wavefront aberration. As is clear 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 center of the light beam when the spherical aberration correction device 7 gives a spherical aberration of −20 mλ when the focus position of the light beam is displaced from the recording surface as shown in FIG. 17A. 3 shows the relationship between the distance from and the wavefront aberration. As is clear 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 if spherical aberrations having the same absolute value are given, 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 influence each other, and the focus position and the spherical aberration amount are not independent of the jitter.

In the above-mentioned conventional optical information processing apparatus, first, the spherical aberration amount that maximizes the amplitude of the focus error signal is searched, and then the focus position that minimizes the jitter value is searched. The search for the amount of spherical aberration and the search for the focus position are performed independently.

However, as described above, since the focus position and the spherical aberration amount both influence the jitter, when the focus position and the spherical aberration amount are searched independently of each other, the initial focus position and the initial spherical aberration amount are detected. Depending on, the convergence result in the exploration may be different. As a result, it may not always be possible to obtain a search result in which the jitter has a true minimum value. If the jitter value obtained as a result of the search deviates from the true minimum value, the quality of the reproduced signal deteriorates. Further, there is a possibility that the recording information and the address information recorded on the optical disc cannot be read normally. Further, when recording on the optical disc, since the recording is performed in a state where the spot of the light flux is expanded, there is a possibility that information cannot be accurately recorded.

The present invention has been made to solve the above problems, and an object thereof is to provide an optical information processing apparatus and an optical information processing method in which the quality of a reproduced signal reproduced from an optical disk is good.

[0026]

In order to achieve the above object, an optical information processing apparatus according to the present invention irradiates an optical information recording medium with light and outputs the light reflected by the optical information recording medium as a head signal. An optical head for converting into and outputting the optical head, a signal quality index detector for detecting a signal quality index representing the quality of the head signal based on the head signal output from the optical head, and irradiation to the optical information recording medium. Two-dimensional search for the focus position and the spherical aberration amount at which the value of the signal quality index detected by the signal quality index detector is optimum by changing the focus position and the spherical aberration amount of the light to be generated. And a probe.

In the present specification, the signal quality index is 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, reproduced signal amplitude, tracking error signal amplitude, focus error signal amplitude, and wobble signal amplitude.

The 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 and converting the light reflected by the optical information recording medium into a head signal for output. A signal quality index detection step of detecting a signal quality index representing the quality of the head signal based on the head signal output in the optical head signal output step; and a focus position of the light with which the optical information recording medium is irradiated. And a spherical aberration amount, by changing the spherical aberration amount and the spherical aberration amount, a two-dimensional searching process for searching the focus position and the spherical aberration amount for which the value of the signal quality index detected by the signal quality index detecting step is optimum. Is characterized by.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION In the optical information processing apparatus according to the present embodiment, the signal quality index detector detects by changing the focus position and the spherical aberration amount of the light irradiated on the optical information recording medium. The two-dimensional probe explores the focus position and the amount of spherical aberration at which the value of the obtained signal quality index is optimum. Therefore, the value of the signal quality index can be optimized based on not only the focus position of the light radiated on the optical information recording medium but also the spherical aberration amount of the light radiated on the optical information recording medium. As a result, it is possible to provide an optical information processing apparatus capable of optimizing the quality of the head signal output from the optical head.

The two-dimensional searcher changes the focus position to search for a focus position where the value of the signal quality index is optimum, and the spherical aberration amount to change the focus position searcher. It is preferable to have a spherical aberration amount probe for searching the spherical aberration amount for which the value of the signal quality index is optimum.

The two-dimensional searcher alternately repeats the search of the focus position by the focus position searcher and the search of the spherical aberration amount by the spherical aberration amount searcher, so that the value of the signal quality index is It is preferable to search for the optimum focus position and 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 n values (n is an integer of 2 or more) within a range ΔX in the variable X are Xi. (I is an integer of 1 or more and n or less), and m values (m is an integer of 2 or more) within the range ΔY in the variable Y are Y.
When j (j is an integer of 1 or more and m or less), the value of the signal quality index is optimized by comparing the values of the signal quality index at each point (Xi, Yj) (Xa , Yb), and by repeating the search around the point (Xa, Yb) while reducing the range ΔX and the range ΔY, the focus position and the spherical aberration amount at which the value of the signal quality index becomes optimum. Is preferred.

In the two-dimensional probe, 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 at which the value of the signal quality index is optimum is searched, and the focus position X is changed at 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, Y
2) A straight line connecting to Y = (Y2-Y1) / (X2-X1)
By changing the focus position X and the spherical aberration amount Y on x (X−X1) + Y1, it is preferable to search the focus position and the spherical aberration amount for which the value of the signal quality index is optimum. .

In the two-dimensional probe, when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y,
By changing the spherical aberration amount Y at a predetermined focus position X1, searching for the spherical aberration amount Y1 at which the value of the signal quality index is optimum, and changing the spherical aberration amount Y at the predetermined focus position X2. Therefore, the spherical aberration amount Y2 for which the value of the signal quality index is optimum
And a straight line connecting the point (X1, Y1) and the point (X2, Y2) Y = (Y2-Y1) / (X2-X1) * (X-X
1) It is preferable to search the focus position and the spherical aberration amount where the value of the signal quality index is optimum by changing the focus position X and the spherical aberration amount Y on + Y1.

In the two-dimensional probe, when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y,
A straight line Y = aX + Y having an inclination a passing through a predetermined spherical aberration amount Y0
By changing the focus position X and the spherical aberration amount Y on a straight line 0, the focus position X1 and the spherical aberration amount Y where the value of the signal quality index is optimum.
1 and changing the focus position X and the spherical aberration amount Y on a straight line Y = − (X−X1) / a + Y1 having a slope −1 / a that passes through the point (X1, Y1). It is preferable to search for the focus position and the spherical aberration amount by which the value of the signal quality index is optimum.

When the wavelength of the light radiated to the optical information recording medium is λ and the numerical aperture is NA, the wavelength λ is 390.
Greater than or equal to nanometer (nm) and less than or equal to 420 nanometer,
It is preferable that the numerical aperture NA is about 0.85, and the value of the slope a is 0.1 λrms / μm or more and 0.3 λrms / μm or less.

The signal quality index detected by the signal quality index detector is jitter, and the two-dimensional searcher can search for the focus position and the spherical aberration amount where the value of the jitter is minimized. preferable.

The signal quality index detected by the signal quality index detector is an error rate, and the two-dimensional searcher searches for a focus position and a spherical aberration amount where the value of the error rate is minimized. It is preferable.

The signal quality indicator detected by the signal quality indicator detector is the amplitude of the reproduced signal,
It is preferable that the dimension searcher searches for the focus position and the spherical aberration amount at which the amplitude value of the reproduction signal is maximized.

The signal quality index detected by the signal quality index detector is the amplitude of the tracking error signal, and the two-dimensional probe uses the focus position and spherical surface where the amplitude value of the tracking error signal is maximum. It is preferable to search the aberration amount.

The signal quality index detected by the signal quality index detector is the amplitude of the wobble signal, and the two-dimensional probe uses the focus position and the spherical aberration amount where the value of the amplitude of the wobble signal is maximum. It is preferable to search for and.

Trial information is recorded on the optical information recording medium, and the head signal converted from the light reflected by the optical information recording medium reproduces the trial information. Preferably, the signal obtained by

The signal quality index includes a focus error signal and a tracking error signal, and the two-dimensional searcher changes the focus position so that the amplitude of the tracking error signal becomes maximum. A focus position probe for searching for a spherical aberration amount probe for searching for a spherical aberration amount that maximizes the amplitude of the focus error signal by changing the spherical aberration amount. It is preferable that the trial information is recorded on the optical information recording medium at the spherical aberration amount where the amplitude of the focus error signal becomes maximum and at the focus position where the amplitude of the tracking error signal becomes maximum.

In the optical information processing method according to the present embodiment, the signal quality detected by the signal quality index detecting step is changed by changing the focus position and the spherical aberration amount of the light applied to the optical information recording medium. The two-dimensional search process searches for the focus position and the amount of spherical aberration for which the index value is optimum. Therefore, it is possible to optimize the value of the signal quality index based on not only the focus position of the light irradiated onto the optical information recording medium but also the spherical aberration amount of the light irradiated onto 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.

In the two-dimensional search step, by changing the focus position, a focus position search step of searching a focus position where the value of the signal quality index is optimum, and by changing the spherical aberration amount,
It is preferable that the method further includes a spherical aberration amount searching step of searching for a spherical aberration amount with which the value of the signal quality index is optimum.

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

In the two-dimensional search 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 Xi. (I is an integer of 1 or more and n or less), and the variable Y
When the value of m (m is an integer of 2 or more) within the range ΔY in Y is (j is an integer of 1 or more and m or less), the value of the signal quality index at each point (Xi, Yj) is By comparing, by searching the point (Xa, Yb) where the value of the signal quality index is optimal, and repeating the searching around the point (Xa, Yb) while reducing the range ΔX and the range ΔY. It is preferable to obtain the focus position and the spherical aberration amount at which the value of the signal quality index is optimum.

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 changed at a predetermined spherical aberration amount Y1 to obtain the signal quality. The focus position X1 for which the index value is optimum is searched, and the focus position X2 for which the signal quality index value is optimized is searched by changing the focus position X at a predetermined spherical aberration amount Y2. X1, Y1) and the point (X2,
A straight line connecting with Y2) Y = (Y2-Y1) / (X2-X
1) Searching the focus position and the spherical aberration amount for which the value of the signal quality index is optimal by changing the focus position X and the spherical aberration amount Y on (X-X1) + Y1. Is preferred.

In the two-dimensional searching step, when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y, the signal quality is changed by changing the spherical aberration amount Y at a predetermined focus position X1. The spherical aberration amount Y1 for which the value of the index is optimum is searched, and the spherical aberration amount Y2 for which the value of the signal quality index is optimized is searched by changing the spherical aberration amount Y at a predetermined focus position X2. A straight line connecting the point (X1, Y1) and the point (X2, Y2) Y = (Y2-Y1) / (X2-X1) * (X
By changing the focus position X and the spherical aberration amount Y on −X1) + Y1, it is preferable to search the focus position and the spherical aberration amount for which the value of the signal quality index is optimum.

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, a straight line Y = aX having a slope a passing through a predetermined spherical aberration amount Y0.
By changing the focus position X and the spherical aberration amount Y on the straight line + Y0, the focus position X1 and the spherical aberration amount Y1 at which the value of the signal quality index is optimum are searched, and the point (X1, Y1 ) Slope passing through -1 /
By changing the focus position X and the spherical aberration amount Y on a straight line Y = − (X−X1) / a + Y1 of a, the focus position and the spherical aberration amount for which the value of the signal quality index is optimum. It is preferable to search for and.

Assuming that the wavelength of the light applied to the optical information recording medium is λ and the numerical aperture is NA, the wavelength λ is 390.
Greater than or equal to nanometer (nm) and less than or equal to 420 nanometer,
It is preferable that the numerical aperture NA is about 0.85, and the value of the slope a is 0.1 λrms / μm or more and 0.3 λrms / μm or less.

The signal quality index detected by the signal quality index detection step is jitter, and the two-dimensional search step can search the focus position and the spherical aberration amount that minimize the jitter value. preferable.

The signal quality index detected by the signal quality index detection step is an error rate, and
In the dimension search step, it is preferable to search the focus position and the spherical aberration amount where the value of the error rate becomes the minimum.

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

The signal quality index detected by the signal quality index detection step is the amplitude of the tracking error signal, and the two-dimensional search step is the focus position and the spherical surface where the amplitude value of the tracking error signal is maximum. It is preferable to search the aberration amount.

The signal quality index detected by the signal quality index detection step is the amplitude of the wobble signal,
In the two-dimensional search step, it is preferable to search the focus position and the spherical aberration amount where the amplitude value of the wobble signal is maximum.

Trial information is recorded on the optical information recording medium, and the head signal converted from the light reflected by the optical information recording medium reproduces the trial information. Preferably, the signal obtained by

The signal quality index includes a focus error signal and a tracking error signal. In the two-dimensional search step, the focus position is changed so that the amplitude of the tracking error signal becomes maximum. A focus position searching step of searching for a spherical aberration amount and a spherical aberration amount searching step of searching a spherical aberration amount that maximizes the amplitude of the focus error signal by changing the spherical aberration amount. In the signal output step, it is preferable that the trial information is recorded on the optical information recording medium at the spherical aberration amount where the amplitude of the focus error signal becomes maximum and at the focus position where the amplitude of the tracking error signal becomes maximum. .

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

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

The optical information processing apparatus 100 has an optical head 5. The optical head 5 is provided with a semiconductor laser 23. The light flux 22 emitted from the semiconductor laser 23 is
After passing through the prism 24, the light 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 passes through the objective lens 9 again, is reflected by the mirror 14, passes through the spherical aberration correction device 7, and is focused by the condenser lens 13. Reflected light 33 focused by the condenser lens 13
Are reflected by the prism 24, and the hologram 15 provided to detect the spherical aberration amount and the cylindrical lens 16 provided to detect the focus position.
After passing through and enters the photodetector 17.

The photodetector 17 generates a head signal based on the incident reflected light 33 and outputs it to the preamplifier 18.
The preamplifier 18 is the photodetector 1 provided in the optical head 5.
The focus error signal FE is generated according to the astigmatism method on the basis of the head signal output from 7 and output 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 between the two, 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 the reproduction signal RF 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 probe 1 as a jitter detection signal JT.

Here, the jitter is a physical quantity representing a time shift of information transition in the reproduced signal. Jitter is closely related to the error rate, which indicates the probability that an error will occur when reading information from an optical disc. Therefore, the jitter is used as an evaluation value of control in the optical information processing device.

The minimum jitter probe 1 has a focus position probe 2. The focus position searcher 11 generates the focus position compensation signal ΔFE and searches the focus position where the value of the jitter detection signal JT is minimized by changing the focus position, and the adder 25
Output to.

A spherical aberration amount probe 3 is provided in the minimum jitter probe 1. The spherical aberration amount exploring device 3 generates the spherical aberration amount compensating signal ΔSAE and outputs it to the adder 26 in order to search the spherical aberration amount for which the value of the jitter detection signal JT is minimized 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 outputs the sum. The result is output to the focus controller 11. Focus controller 1
1 is based on the addition result output from the adder 25,
Focus actuator 10 provided on the optical head 5
Output a control signal to. Focus actuator 10
Drives the objective lens 9 along the direction perpendicular to the optical disc 6 so as to control the focus position of the light flux that converges on the optical disc 6, based on the control signal output from the focus controller 11. Focus control is executed in this manner.

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 exploration device 3, and controls the result to control the spherical aberration amount. Output to the container 12. 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 based on the addition result output from the adder 26. The spherical aberration correction actuator 8 corrects the spherical aberration generated due to the thickness error of the protective layer formed on the optical disc 6 based on the control signal output from the spherical aberration controller 12. The degree of divergence of the light flux is changed by changing the distance between the two lenses provided in the aberration correction device 7.

FIG. 4 is a graph showing the characteristics of jitter with respect to the focus position and the amount of spherical aberration in the optical information processing device 100. The horizontal axis indicates the focus position of the light beam irradiated onto the optical disc 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 disc 6. The value of jitter is shown by a contour map composed of a plurality of concentric ellipses. The jitter values are equal on the outer circumference of each ellipse, and the closer to the center of each ellipse, the smaller the jitter value. Therefore, the jitter value becomes the minimum at the center of each ellipse.

As shown in FIG. 4, each ellipse has its major and minor axes inclined with respect to the horizontal and vertical axes.
This means that the focus position and the amount of spherical aberration affect 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 they must be adjusted 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 executes such a two-dimensional probe, and is composed of a microprocessor, for example, in the optical information processing apparatus 100 according to the present embodiment. If the minimum-jitter probe 1 is composed of a microprocessor, the two-dimensional probe can be easily realized by programming even if the method of the two-dimensional probe is somewhat complicated.

FIG. 5 is a graph for explaining the two-dimensional search by the optical information processing device 100. Similar to FIG. 4 described above, the horizontal axis represents the focus position of the light beam, and the vertical axis represents the spherical aberration amount. The value of jitter is shown by a contour map composed of a plurality of concentric ellipses. Hereinafter, in order to simplify the description, 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 has a predetermined spherical aberration amount Y = Y ₁
The focus position X _{1 at} which the jitter value is minimized is searched by changing the focus position X on the straight line. Then, the spherical aberration amount probe 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 . By alternately repeating 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 as shown by the zigzag polygonal line drawn in FIG. As described above, the value of the jitter decreases, and the value of the jitter does not decrease further by both 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. When the hit state is reached, the search is repeated. 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 the operation for the two-dimensional search by the optical information processing device 100. First, in step S1, initial values of the focus position X and the spherical aberration amount Y are set. As an initial value,
A preset value with small jitter so that the signal can be reproduced is used by simulation or the like. Then, in step S2, the focus position searcher 11 changes the focus position X by ΔX. Then, the jitter detector 4 measures the jitter. Next, in step S3, the focus position searcher 11 determines whether or not the measured jitter value has become minimum. The focus position searcher 11 changes the focus position X until the jitter value becomes the minimum. If the jitter is minimized (YES in step S3), the process proceeds to step S4.

In step S4, the spherical aberration amount probe 3
Changes the spherical aberration amount Y by ΔY. Then, the jitter detector 4 measures the jitter. Then, in step S5, the spherical aberration amount probe 3 determines whether or not the measured jitter value is minimum. The process returns to step S4 until the value of the jitter becomes the minimum, and the spherical aberration amount probe 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 detector 1 determines whether or not the minimum jitter value has converged, and steps S2 to S5 are repeated until the minimum jitter value converges. The convergence determination condition for determining whether or not the minimum jitter value has converged may be that the change in the minimum jitter value is equal to or less than a preset value. When the minimum jitter value converges (YES in step S6), the two-dimensional search ends.

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

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

The jitter, error rate and reproduction signal are
It can be obtained by reproducing a track on which disc information, address and data are recorded by 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 the recording signal generating means, is recorded on the optical disc 6 by the optical head 5, and the recorded test information is recorded. By reproducing, the jitter, the error rate and the reproduced signal can be obtained.

At this time, experimental information is obtained at the spherical aberration amount where the amplitude of the focus error signal is maximized in the spherical aberration probe 3 and at the focus position where the amplitude of the tracking error signal is maximized in the focus position probe 11. By recording, it is possible to record with the spot narrowed down. Also, the recorded trial information is
It may be erased 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 search by the optical information processing device 100. Similar to FIG. 5 described above, the horizontal axis represents the focus position of the light beam, and the vertical axis represents the spherical aberration amount. The value of jitter is shown by a contour map composed of a plurality of concentric ellipses.

First, the minimum jitter searcher 1 searches for the point where the jitter value is the minimum 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 have a side length of ΔX along the X-axis direction and Y
Each of the vertices of a rectangle whose side length along the axial direction is ΔY is formed. 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 where the value of the jitter searched by the minimum jitter searcher 1 is the minimum is the point A ₀ .

Next, the minimum jitter probe 1 has five points A
_{Of 0} , B ₁ , B ₂ , B ₃ and B ₄ , the point where the jitter value is the minimum is searched. Points B ₁ , B ₂ , B ₃ and B ₄ are points A
Each of the vertices of a rectangle centered at ₀ is formed.
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 than. In the contour map shown in FIG. 7,
The point where the value of the jitter detected by the minimum jitter detector 1 is the minimum is the point B ₃ .

Then, when the above-described search is repeated by further reducing ΔX and ΔY around the point B ₃ where the jitter obtained by this search is the minimum, the value of the jitter is reduced. When the jitter value reaches the bottom state where it does not decrease any more, the repeated search is terminated. In this way, the focus position and the spherical aberration amount that minimize the jitter value can be obtained. This exploration method is shown in FIG.
It is possible to reduce the number of jitter measurement points as compared with the search method described above with reference to FIG. Therefore, the search can be performed faster than the search method described above with reference to FIG.

FIG. 8 is a flow chart showing the operation for another two-dimensional search by the optical information processing apparatus 100.
First, in step S11, the minimum jitter probe 1 sets initial values of the focus position X and the spherical aberration amount Y. As an initial value, a preset value with a small jitter so that a signal can be reproduced is used by an experiment, a simulation, or the like. Then, in step S12, the minimum jitter probe 1 has Δ centered on the initial value (X, Y).
Five measurement points included in the range of X and ΔY are set.
Next, in step S13, the jitter detector 4 measures the values of the jitter at the five measurement points, and the minimum jitter probe 1 searches for the measurement point having the smallest jitter among the five measurement stores.

Then, in step S14, the minimum jitter detector 1 determines whether or not the minimum jitter value has converged. The convergence determination condition may be, for example, when the change in the minimum jitter value is equal to or less than a preset value, when the measured jitter values at five measurement points are the same value, or the like.

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 S are performed.
Repeat 13. When it is determined that the minimum jitter value has converged (YES in step S14), the two-dimensional search ends. As described above, the focus control and the spherical aberration control can be accurately performed by performing the two-dimensional search for obtaining the focus position and the spherical aberration amount that minimize the jitter.

In the present embodiment, ΔX, Δ
An example in which the number of jitter measurement points included in the Y range is set to 5 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 probe 1 defines the focus position as the variable X and the spherical aberration amount as the variable Y, and n pieces within the range ΔX in the variable X (n is n A value of 2 or more) is Xi (i is an integer of 1 or more and n or less), and m (m is 2) within a range ΔY in the variable Y.
When the value of (the above integer) is Yj (j is an integer of 1 or more and m or less), by comparing the jitter values at the respective points (Xi, Yj), the point where the jitter value becomes the minimum ( Xa, Yb) is searched, and the search is repeated around the point (Xa, Yb) while reducing the range ΔX and the range ΔY. Therefore, 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 search by the optical information processing device 100. Similar to FIG. 7 described above, the horizontal axis shows the focus position of the light beam, and the vertical axis shows the spherical aberration amount. The value of jitter is shown by a contour map composed of a plurality of concentric ellipses.

First, the minimum jitter probe 1 is a predetermined spherical surface.
Aberration amount Y = Y₁Change the focus position X on the straight line
Position X that minimizes the jitter value₁To
Explore. Next, the minimum jitter probe 1
Surface aberration amount Y = Y₂Focus position X on the straight line
Focus position X where the jitter value is minimized by changing ₂
To explore.

Then, the minimum jitter probe 1 uses the straight line Y = (Y ₂ which connects the point (X ₁ , Y ₁ ) and the point (X ₂ , Y ₂ ).
-Y ₁ ) / (X ₂ −X ₁ ) × (X−X ₁ ) + Y _{1 On} the straight line, the focus position X and the spherical aberration amount Y are changed to minimize the jitter value. Explore quantity and. This search method can further reduce the number of jitter measurement points as compared with the search method described above with reference to FIG. 7. Therefore, the search can be performed at a higher speed than the search method described above with reference to FIG. 7.

FIG. 10 is a flowchart showing the operation of the optical information processing apparatus 100 for still another two-dimensional search. First, in step S31, initial values of the focus position X and the spherical aberration amounts Y ₁ and Y ₂ are set.
As an initial value, by experiment, simulation, etc.,
A preset value with a small jitter so that the signal can be reproduced is used. Then, in step S32, the focus position X is changed by ΔX on the straight line of the spherical aberration amount Y ₁ , and the jitter is measured. Next, step S33.
At, it is determined whether the measured jitter value is the minimum. When it is determined that the measured jitter value is not the minimum (NO in step S33), the process returns to step S32 until the jitter value becomes the minimum, and the focus position X is reached.
Change. When it is determined that the measured jitter value is the minimum (YES in step S33), the process proceeds to step S34.

Then, in step S34, the focus position X is changed by ΔX on the straight line of the spherical aberration amount Y ₂ , and the jitter is measured. Next, step S35.
At, it is determined whether the measured jitter value is the minimum. When it is determined that the measured jitter value is not the minimum value (NO in step S35), the process returns to step S34 until the jitter value becomes the minimum value.
Change. When it is determined that the measured jitter value is the minimum (YES in step S35), the process proceeds to step S36.

Then, in step S36, the four
By changing the dust position X by ΔX, the spherical aberration amount Y becomes
(X₁, Y₁) And point (X₂, Y₂) An expression Y that represents a straight line connecting
= (Y ₂-Y₁) / (X₂-X₁) × (XX₁) + Y₁To X
Jitter is measured as a value obtained by substituting That
Then, in step S37, the measured jitter value is the maximum.
Determine whether it has become small. The measured jitter value is the highest.
When it is determined that it is not small (N in step S37
O), until the jitter value becomes the minimum, go to step S36.
The return focus position X and spherical aberration amount Y are changed.
It When it is determined that the measured jitter value is the minimum
(YES in step S37) End two-dimensional exploration
To do.

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 probe 1 has the focus position X at the predetermined spherical aberration amount Y1. By changing the focus position X1 with the minimum jitter value, and by changing the focus position X at a predetermined spherical aberration amount Y2, the focus position X2 with the minimum jitter value is searched. Point (X1, Y1) and point (X2, Y
2) A straight line connecting to Y = (Y2-Y1) / (X2-X1)
By changing the focus position X and the spherical aberration amount Y on × (X−X1) + Y1, the focus position and the spherical aberration amount that minimize the jitter value are searched. Therefore, the focus position and the spherical aberration amount that minimize the jitter value can be obtained accurately and at high speed.

It should be noted that the predetermined spherical aberration amount Y = Y ₁ and Y
= Y ₂ of were subjected to exploration focus position X under, perform exploration spherical aberration Y under a predetermined focus position X = X ₁ and X = X _2, the same as the above exploration It goes without saying that you can do it.

FIG. 11 is a graph for explaining still another two-dimensional search by the optical information processing device 100. First, the minimum jitter probe 1 changes the focus position X and the spherical aberration amount Y on the straight line Y = aX + Y _{0 having} the inclination 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 probe 1 determines the focus position X and the amount of spherical aberration on the straight line Y = − (X−X ₁ ) / a + Y _{1 with} the slope −1 / a passing through the points (X ₁ , Y ₁ ). By changing Y and Y, the focus position and the spherical aberration amount that minimize the jitter value are searched.

The slope a is determined according to the numerical aperture, wavelength and recording method. The inclination a is 0.1 λrms / μm or more,
When set to a value of 0.3 λrms / μm or less (λ is the wavelength of light), it has a numerical aperture NA of 0.85 and a wavelength of 390
This is effective when using an optical head that irradiates the optical disc with light of not less than nanometer and not more than 420 nanometer.

This exploration method utilizes the fact that the major axis and the minor axis of each ellipse forming the contour map representing the jitter characteristic 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 with reference to FIG.
Therefore, the search can be performed at a higher speed than the search method described above with reference to FIG.

FIG. 12 is a flowchart showing the operation of the optical information processing apparatus 100 for still another two-dimensional search. First, in step S41, initial values of the inclination a and the spherical aberration amount Y ₀ are set. As an initial value,
A preset value with a small jitter so that the signal can be reproduced is used by an experiment, a simulation, or the like. Then, in step S42, the focus position X is set to ΔX.
Change the spherical aberration amount Y into the formula Y = aX + Y ₀
Then, the jitter is measured.

Next, in step S43, it is determined whether or not the measured jitter value is the minimum. When it is determined that the measured jitter value is not the minimum (step S4
No. 3), the process returns to step S42 until the jitter value becomes the minimum, and the focus position X and the spherical aberration amount Y
Change. When it is determined that the measured jitter value is the minimum (YES in step S43), the process proceeds to step S44.

Then, in step S44, the focus position X is changed by ΔX, and the spherical aberration amount Y is calculated by the equation Y
== (X−X ₁ ) / a + Y ₁ is a value obtained by substituting X, and the jitter is measured. Next, in step S45, it is determined whether or not the measured jitter value is minimized. When it is determined that the measured jitter value is not the minimum (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 minimum. When it is determined that the measured jitter value is minimum (YES in step S45), the two-dimensional search is ended.

As described above, according to this 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 probe 1 has a slope 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 Y = aX + Y0, the focus position X1 and the spherical aberration amount Y1 at which the jitter values are optimal are searched for, and the point (X1, Y1) By changing the focus position X and the spherical aberration amount Y on a straight line Y = − (X−X1) / a + Y1 having a slope of −1 / a that passes through the focus position and the spherical aberration Explore quantity and. Therefore, the focus position and the spherical aberration amount that minimize the jitter value can be obtained accurately and at high speed.

In the above-described embodiment, 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. However, the present invention is not limited to this.
The amount of spherical aberration may be corrected by the 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 this embodiment, and FIG. 14 is another optical head 5A.
3 is a front view of the liquid crystal element 31 provided in FIG. The same components as those of the optical head 5 described above with reference to FIG. 2 are designated by the same reference numerals. Therefore, detailed description of these components will be omitted. The difference from the above-described optical head 5 is that the liquid crystal element 3 is used instead of the spherical aberration correction device 7.
It is a point that is equipped with 1. As shown in FIG. 14, the electrodes provided on the liquid crystal element 31 are divided into a plurality of regions by a plurality of concentric circles. The liquid crystal element 3 is adjusted by adjusting the voltage applied to each electrode provided in each region.
The spherical aberration amount can be corrected by adjusting the phase difference of the light passing through 1.

[0107]

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 reproduced signal reproduced from an optical disk is good.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical information processing apparatus according to this embodiment.

FIG. 2 is a block diagram for explaining a configuration of an optical head provided in the optical information processing device according to the present embodiment.

FIG. 3 is a block diagram showing a configuration of a minimum jitter prober provided in the optical information processing device according to the present embodiment.

FIG. 4 is a graph showing characteristics of jitter with respect to a focus position and a spherical aberration amount in the optical information processing device according to the present embodiment.

FIG. 5 is a graph for explaining a two-dimensional search by the optical information processing device according to the present embodiment.

FIG. 6 is a flowchart showing an operation for two-dimensional search by the optical information processing device according to the present embodiment.

FIG. 7 is a graph for explaining another two-dimensional search by the optical information processing device according to the present embodiment.

FIG. 8 is a flowchart showing an operation for another two-dimensional search by the optical information processing device according to the present embodiment.

FIG. 9 is a graph for explaining still another two-dimensional search by the optical information processing device according to the present embodiment.

FIG. 10 is a flowchart showing an operation for still another two-dimensional search by the optical information processing device according to the present embodiment.

FIG. 11 is a graph for explaining still another two-dimensional search by the optical information processing device according to the present embodiment.

FIG. 12 is a flowchart showing an operation for still another two-dimensional search by the optical information processing device according to the present embodiment.

FIG. 13 is a block diagram for explaining the configuration of another optical head provided in the optical information processing device according to the present embodiment.

FIG. 14 is a front view of a liquid crystal element provided in another optical head according to the present embodiment.

FIG. 15 is a block diagram showing a configuration of a conventional optical information processing device.

FIG. 16 is a block diagram for explaining a configuration of an optical head provided in a conventional optical information processing device.

17A to 17C are graphs showing the relationship between the wavefront aberration and the distance from the center of the light beam.

[Explanation of symbols]

1 Minimum jitter probe 2 Focus position probe 3 Spherical aberration probe 4 Jitter detector 5 optical head 6 optical disks 7 Spherical aberration correction device 8 Spherical aberration correction actuator 9 Objective lens 10 Focus actuator 11 Focus controller 12 Spherical aberration amount controller 13 Condensing lens 14 mirror 15 hologram 16 Cylindrical lens 17 Photodetector 18 preamplifier 25,26 adder

Continued front page    (72) Inventor Akimasa Sano             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Yuichi Kuze             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 2H051 AA14 CD12 CD29 CD30                 5D118 AA14 CA11 CD02 CD06 CF10                 5D789 AA09 BA01 EA03 EC01 JA09

Claims (30)

[Claims] 1. An optical head which irradiates an optical information recording medium with light, converts the light reflected by the optical information recording medium into a head signal and outputs the head signal, and the head signal output from the optical head. A signal quality index detector that detects a signal quality index representing the quality of the head signal based on the signal quality, by changing the focus position and the spherical aberration amount of the light irradiated to the optical information recording medium, An optical information processing apparatus, comprising: a two-dimensional searcher that searches a focus position and a spherical aberration amount where the value of the signal quality index detected by the index detector is optimum. 2. The two-dimensional probe is configured to change the focus position to detect a focus position where the value of the signal quality index is optimum, and to change the spherical aberration amount. The optical information processing apparatus according to claim 1, further comprising: a spherical aberration amount probe that searches for the spherical aberration amount for which the value of the signal quality index is optimum. 3. 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 to obtain the signal quality index. The optical information processing apparatus according to claim 2, wherein a focus position and a spherical aberration amount having optimum values are searched. 4. The two-dimensional probe defines the focus position as a variable X and the spherical aberration amount as a variable Y, and n values (n is an integer of 2 or more) within a range ΔX in the variable X. Is Xi (i is an integer of 1 or more and n or less), and the variable Y is
When the value of m (m is an integer of 2 or more) within the range ΔY in Y is (j is an integer of 1 or more and m or less), the value of the signal quality index at each point (Xi, Yj) is By comparing, the point (Xa, Yb) where the value of the signal quality index is optimum is searched, and the point (Xa, Yb is reduced while the range ΔX and the range ΔY are reduced.
By repeating the exploration around b),
The optical information processing apparatus according to claim 1, wherein a focus position and a spherical aberration amount that optimize the value of the signal quality index are obtained. 5. The two-dimensional probe, when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y, changes the focus position X at a predetermined spherical aberration amount Y1. The focus position X1 where the value of the signal quality index is optimum is searched, and the focus position X2 where the value of the signal quality index is optimum is searched by changing the focus position X at a predetermined spherical aberration amount Y2, A straight line Y = that connects the point (X1, Y1) and the point (X2, Y2)
(Y2-Y1) / (X2-X1) * (X-X1) + Y1
On the top, the focus position X and the spherical aberration amount Y
By changing and, the focus position and the spherical aberration amount for which the value of the signal quality index is optimal are searched,
The optical information processing device according to claim 1. 6. The two-dimensional probe, when the focus position is defined as a variable X and the spherical aberration amount is defined as a variable Y, by changing the spherical aberration amount Y at a predetermined focus position X1, The spherical aberration amount Y1 for which the value of the signal quality index is optimum is searched, and the spherical aberration amount Y2 for which the value of the signal quality index is optimized is searched by changing the spherical aberration amount Y at a predetermined focus position X2. Then, a straight line Y = that connects the point (X1, Y1) and the point (X2, Y2)
(Y2-Y1) / (X2-X1) * (X-X1) + Y1
On the top, the focus position X and the spherical aberration amount Y
By changing and, the focus position and the spherical aberration amount for which the value of the signal quality index is optimal are searched,
The optical information processing device according to claim 1. 7. The two-dimensional probe, when the focus position is defined as a variable X and the spherical aberration amount as a variable Y, a straight line Y = aX + Y having a slope a passing through a predetermined spherical aberration amount Y0.
By changing the focus position X and the spherical aberration amount Y on a straight line 0, the focus position X1 and the spherical aberration amount Y where the value of the signal quality index is optimum.
1 and a straight line Y =-(X with an inclination of -1 / a passing through the point (X1, Y1)
The focus position and the spherical aberration amount for which the value of the signal quality index is optimum are searched by changing the focus position X and the spherical aberration amount Y on a straight line −X1) / a + Y1. The optical information processing device described. 8. The wavelength λ is 39 when the wavelength of the light radiated to the optical information recording medium is λ and the numerical aperture is NA.
The nanometer (nm) or more and 420 nanometers or less, the numerical aperture NA is about 0.85, and the value of the inclination a is 0.1 λrms / μm or more and 0.3λrms / μm or less. Optical information processing device. 9. The signal quality index detected by the signal quality index detector is jitter, and the two-dimensional searcher searches for a focus position and a spherical aberration amount that minimize the value of the jitter. The optical information processing device according to claim 1. 10. The signal quality index detected by the signal quality index detector is an error rate, and the two-dimensional probe uses a focus position and a spherical aberration amount with which the value of the error rate is minimized. Exploring, claim 1
The optical information processing device described. 11. The signal quality index detected by the signal quality index detector is an amplitude of a reproduction signal, and the two-dimensional probe is a focus position and a spherical surface where a value of the amplitude of the reproduction signal is maximum. The optical information processing apparatus according to claim 1, which searches for the aberration amount. 12. The signal quality index detected by the signal quality index detector is the amplitude of a tracking error signal, and the two-dimensional probe is a focus position where the value of the amplitude of the tracking error signal is maximum. The optical information processing device according to claim 1, wherein the optical information processing device searches for the spherical aberration amount and the spherical aberration amount. 13. The signal quality index detected by the signal quality index detector is the amplitude of a wobble signal, and the two-dimensional searcher is configured such that a focus position and a spherical surface at which the value of the amplitude of the wobble signal becomes maximum. The optical information processing apparatus according to claim 1, which searches for the aberration amount. 14. The optical head irradiates the optical information recording medium with light to record test information, and the head signal converted from the light reflected by the optical information recording medium is The optical information processing apparatus according to claim 1, wherein the optical information processing apparatus is a signal obtained by reproducing experimental information. 15. The signal quality indicator includes a focus error signal and a tracking error signal, and the two-dimensional probe maximizes the amplitude of the tracking error signal by changing the focus position. A focus position searcher for searching a focus position, and a spherical aberration amount searcher for changing the spherical aberration amount to search for a spherical aberration amount that maximizes the amplitude of the focus error signal, 15. The optical head records the trial information on the optical information recording medium at a spherical aberration amount where the amplitude of the focus error signal becomes maximum and at a focus position where the amplitude of the tracking error signal becomes maximum. The optical information processing device described. 16. An optical head signal outputting 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 outputting in the optical head signal outputting step. A signal quality index detecting step of detecting a signal quality index indicating the quality of the head signal based on the head signal generated, and changing a focus position and a spherical aberration amount of the light with which the optical information recording medium is irradiated. Accordingly, the optical information processing method includes a two-dimensional search step of searching a focus position and a spherical aberration amount where the value of the signal quality index detected by the signal quality index detection step is optimum. . 17. The focus position searching step of searching the focus position where the value of the signal quality index is optimum by changing the focus position, and the spherical aberration amount is changed in the two-dimensional search step. 17. The optical information processing method according to claim 16, further comprising: a spherical aberration amount exploring step of exploring a spherical aberration amount for which the value of the signal quality index is optimum. 18. The signal quality index of the two-dimensional search step is determined by alternately repeating the search of the focus position by the focus position search step and the search of the spherical aberration amount by the spherical aberration amount search step. The optical information processing method according to claim 17, wherein the focus position and the spherical aberration amount having the optimum values are searched. 19. In the two-dimensional search 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 defined. Is Xi (i is an integer of 1 or more and n or less), and m in the range ΔY in the variable Y (m is an integer of 2 or more)
Is Yj (j is an integer of 1 or more and m or less), the value of the signal quality index is optimized by comparing the values of the signal quality index at each point (Xi, Yj). The point (Xa, Yb) is searched and the point (Xa, Yb is reduced while the range ΔX and the range ΔY are reduced.
By repeating the exploration around b),
17. The optical information processing method according to claim 16, wherein the focus position and the spherical aberration amount at which the value of the signal quality index is optimum are obtained. 20. 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 changed at a predetermined spherical aberration amount Y1, The focus position X1 where the value of the signal quality index is optimum is searched, and the focus position X2 where the value of the signal quality index is optimum is searched by changing the focus position X at a predetermined spherical aberration amount Y2, A straight line Y = that connects the point (X1, Y1) and the point (X2, Y2)
(Y2-Y1) / (X2-X1) * (X-X1) + Y1
On the top, the focus position X and the spherical aberration amount Y
By changing and, the focus position and the spherical aberration amount for which the value of the signal quality index is optimal are searched,
The optical information processing method according to claim 16. 21. 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, by changing the spherical aberration amount Y at a predetermined focus position X1, The spherical aberration amount Y1 for which the value of the signal quality index is optimum is searched, and the spherical aberration amount Y2 for which the value of the signal quality index is optimized is searched by changing the spherical aberration amount Y at a predetermined focus position X2. Then, a straight line Y = that connects the point (X1, Y1) and the point (X2, Y2)
(Y2-Y1) / (X2-X1) * (X-X1) + Y1
On the top, the focus position X and the spherical aberration amount Y
By changing and, the focus position and the spherical aberration amount for which the value of the signal quality index is optimal are searched,
The optical information processing method according to claim 16. 22. 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, a straight line Y = aX + Y having a slope a passing through a predetermined spherical aberration amount Y0.
By changing the focus position X and the spherical aberration amount Y on a straight line 0, the focus position X1 and the spherical aberration amount Y where the value of the signal quality index is optimum.
1 and a straight line Y =-(X with an inclination of -1 / a passing through the point (X1, Y1)
17. The focus position and the spherical aberration amount for which the value of the signal quality index is optimum is searched by changing the focus position X and the spherical aberration amount Y on a straight line −X1) / a + Y1. The optical information processing method described. 23. When the wavelength of the light with which the optical information recording medium is irradiated is λ and the numerical aperture is NA, the wavelength λ is 3
The nanometer (nm) or more and 420 nanometer or less, the numerical aperture NA is about 0.85, and the value of the slope a is 0.1 λrms / μm or more and 0.3λrms / μm or less. Optical information processing method. 24. 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 that minimize the value of the jitter. The optical information processing method according to claim 16. 25. The signal quality index detected by the signal quality index detection step is an error rate, and the two-dimensional search step includes a focus position and a spherical aberration amount that minimize the value of the error rate. The optical information processing method according to claim 16, wherein the optical information processing is performed. 26. 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 includes a focus position and a spherical surface at which an amplitude value of the reproduction signal becomes maximum. The optical information processing method according to claim 16, wherein the aberration amount is searched. 27. The signal quality index detected by the signal quality index detection step is the amplitude of a tracking error signal, and the two-dimensional search step is a focus position where the amplitude value of the tracking error signal is maximum. The optical information processing method according to claim 16, further comprising: searching for the spherical aberration amount and the spherical aberration amount. 28. 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 includes a focus position and a spherical surface where a value of the amplitude of the wobble signal is maximum. To investigate the amount of aberration,
The optical information processing method according to claim 16. 29. 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 reproduces the test information. The optical information processing method according to claim 16, which is a signal obtained by 30. The signal quality index includes a focus error signal and a tracking error signal, and in the two-dimensional search step, the amplitude of the tracking error signal is maximized by changing the focus position. A focus position searching step of searching a focus position, and a spherical aberration amount searching step of searching a spherical aberration amount in which the amplitude of the focus error signal is maximized by changing the spherical aberration amount, Before the optical head signal output step, the trial information is recorded on the optical information recording medium at the spherical aberration amount where the amplitude of the focus error signal becomes maximum and at the focus position where the amplitude of the tracking error signal becomes maximum. 30. The optical information processing method according to claim 29, further comprising a step of recording an optical head.