JP2002319160A - Signal recording device and signal recording method, signal reproducing device and signal reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal recording device which stably carries out gap control to control the distance between an optical means and an optical recording medium in a proximity field, and to provide a signal recording method, a signal reproducing device and a signal reproducing method. SOLUTION: In a band-limited circuit 20, the frequency band of an inputted return light quantity S1 is limited within a gap control band, and a return light quantity S2 after a band limitation not influenced by a modulation by the information source 1 of a laser beam LB1 for recording, the surface roughness of a glass master disk 17, the resonance of an exposure device, etc., is outputted. The return light quantity S2 after the band limitation is inputted in a gap controller 21, and gap control to fix the distance between an optical head 16 and a glass master disk 17 is carried out by a gap control voltage S3 outputted from the gap controller 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal recording apparatus and a signal recording method for recording a signal on an optical recording medium using near-field light, and to reproduce a signal from the optical recording medium using near-field light. The present invention relates to a signal reproducing device and a signal reproducing method.

[0002]

2. Description of the Related Art For example, a signal recording apparatus and a signal reproducing apparatus such as an optical disk apparatus for recording and reproducing signals on and from an optical disk, and an exposure apparatus for recording a signal by exposing a glass master used for producing an optical disk stamper. For recording and reproducing the signal, a method using near-field light by a converging lens using a solid immersion lens has been proposed. As such a solid immersion lens, an SIL (Solid Immersion) that constitutes a second lens unit in combination with a condenser lens is used.
sion lens) and SIM (Solid Immersi)
on Mirror). By using the near-field light from the converging lens using this solid immersion lens for recording and reproducing signals on optical discs, etc., the diameter of the condensed spot on optical discs, etc. can be further increased in response to the need for higher density optical discs. It is possible to miniaturize.

For example, the SIL is a high refractive index lens having a shape obtained by cutting off a part of a spherical lens, and is interposed between a condenser lens and an optical disk. This SIL is
The spherical surface is arranged on the side of the condenser lens, and the opposite surface faces the signal recording surface of the optical disk.

In order to perform recording or reproduction on an optical disk or the like using such an SIL, a laser beam transmitted through a condenser lens is condensed on the SIL, and an end face (SI
L) and the signal recording surface of the optical disk are brought close to a distance at which near-field light is generated (about ２ or less of the wavelength of the light). It is necessary to perform gap control for making the distance between the optical disk and the signal recording surface of the optical disk constant, and to make the focused spot on the optical disk constant. This gap control is performed, for example, when the amount of light returning from the SIL is
This is performed by detecting the distance between the SIL and the optical disk based on the change in the amount of light returning from the SIL, utilizing the fact that the distance between the SIL and the optical disk has linear characteristics.

[0005]

However, in the above-described gap control, in the near field region (near field region) between the SIL and the optical disk, the SI
The amount of light returned from L becomes the modulation signal itself accompanying recording and reproduction, and is directly affected by the modulation. For this reason, there is a problem that the quality of the recording or reproduction signal is deteriorated.

Further, since the amount of light returned from the SIL may fluctuate at a high frequency due to surface roughness of the optical disk or resonance of the optical disk device, the quality of a recording or reproduction signal is degraded due to an increase in a gap error. There was a problem of doing it. For example, even when the mirror surface of an optical disk is reproduced by an optical disk device, or when a groove is recorded on a glass master by an exposure device, the amount of return light is not affected by modulation,
There is a problem that the amount of return light fluctuates at a high frequency due to surface roughness of the glass master or resonance of the optical disk device and the exposure device, and the quality of the signal deteriorates. This is because the surface of an optical disk or the like or the frequency of resonance of an optical disk device or the like is several kHz, which is close to the gap control band of several kHz.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object thereof is to stably perform a gap control for controlling a distance between an optical unit and an optical recording medium in a near-field region. A signal recording device and a signal recording method, and a signal reproducing device and a signal reproducing method are provided.

[0008]

A signal recording apparatus according to the present invention is a signal recording apparatus for recording a signal on an optical recording medium by using near-field light. An optical unit that is disposed close to the signal recording surface, receives a laser beam emitted from a light source, and condenses near-field light by the laser beam onto the optical recording medium; and detects an amount of light returned from the optical unit and the optical recording medium. Return light amount detection means, return light amount correction means for correcting the return light amount to a signal whose frequency band is limited, and control of the distance between the optical means and the optical recording medium according to the return light amount corrected by the return light amount correction means. Gap control means.

A signal recording method according to the present invention is a signal recording method for recording a signal on an optical recording medium using near-field light. The signal recording method is disposed close to a signal recording surface of the optical recording medium and emitted from a light source. By the optical means to which laser light is incident,
The near-field light caused by the laser light is focused on the optical recording medium, the amount of return light from the optical unit and the optical recording medium is detected, and the detected amount of return light is corrected to a signal having a limited frequency band. The distance between the optical means and the optical recording medium is controlled according to the return light amount corrected by limiting the band.

A signal reproducing apparatus according to the present invention is a signal reproducing apparatus for reproducing a signal from an optical recording medium using near-field light. Arranged, a laser beam emitted from a light source is incident thereon, an optical unit that focuses near-field light by the laser beam on the optical recording medium, and an optical unit and a return light amount detecting unit that detects a return light amount from the optical recording medium. Return light amount correction means for correcting the return light amount to a signal whose frequency band is limited, and gap control means for controlling the distance between the optical means and the optical recording medium according to the return light amount corrected by the return light amount correction means. Have.

A signal reproducing method according to the present invention is a signal reproducing method for reproducing a signal from an optical recording medium using near-field light. The signal reproducing method is arranged close to a signal recording surface of an optical recording medium and emitted from a light source. By the optical means to which the laser light is incident, the near-field light by the laser light is focused on the optical recording medium,
The amount of return light from the optical unit and the optical recording medium is detected, the detected amount of return light is corrected to a signal whose frequency band is limited, and the optical unit is corrected according to the amount of return light corrected by limiting this frequency band. To control the distance between the optical recording medium.

In the signal recording apparatus and the signal recording method according to the present invention, when recording a signal on an optical recording medium using near-field light, the frequency band is limited by the amount of return light from the optical means and the optical recording medium. In order to correct the signal, the return light amount is converted into a signal which is not affected by the modulation of the recording signal, but is also not affected by the roughness of the signal recording surface of the optical recording medium and the resonance of the signal recording device. In accordance with the corrected return light amount, stable gap control is performed so that the distance between the optical unit and the optical recording medium becomes constant.

In the signal reproducing apparatus and the signal reproducing method according to the present invention, when reproducing a signal from an optical recording medium using near-field light, the amount of return light from the optical means and the optical recording medium is limited by a frequency band. In order to correct the signal, the amount of return light is converted into a signal which is not affected not only by the modulation of the reproduction signal but also by the roughness of the signal recording surface of the optical recording medium and the resonance of the signal reproducing device. . In accordance with the corrected amount of return light, stable gap control is performed so that the distance between the optical unit and the optical recording medium becomes constant.

[0014]

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

[First Embodiment] FIG. 1 shows a configuration of an exposure apparatus which is a signal recording apparatus according to a first embodiment of the present invention. This exposure apparatus is, specifically, a cutting machine that irradiates a laser beam modulated in accordance with information onto the surface of the glass master 17 coated with a resist to cut and record information. The glass master 17 which is an optical recording medium on which the cutting recording is performed is used.
Is used to create a stamper for an optical disk.

This exposure apparatus comprises an information source 1, a recording signal generator 2, and an acousto-optical device (AOM: Acousto Optical M).
odulator) 3, a laser element 4 serving as a light source for emitting the recording laser beam LB1, and an electro-optical modulator (EO)
M: Electro Optical Modulator) 5 and analyzer 6
, A beam splitter (BS) 7, a first photodetector (PD1) 8a, and a second returning light amount detecting unit.
A photodetector (PD2) 8b, an auto power controller (APC) 9
A first mirror 10a, a second mirror 10b, a third mirror 10c, a first condenser lens 11a, a second condenser lens 11b, a collimator lens 12, and a polarizing beam splitter (PBS) 13, a λ / 4 plate 14, and an optical head 16 which is attached to the piezo element 15 and includes, for example, a condenser lens 16a which is an aspherical lens and an SIL 16b which is a solid immersion lens. . The optical head 16 is an optical unit that is disposed close to a signal recording surface of a glass master 17 as an irradiation target, and focuses near-field light by the recording laser light LB1 on the glass master 17.

Further, this exposure apparatus limits the frequency band of the light amount (return light amount S1) of the return light LB2 from the optical head 16, performs band limitation, and outputs the return light amount S2 after the band limitation. A band limiting circuit 20 which is
A gap control means for outputting a gap control voltage S3 in accordance with the return light quantity S2 after the band limitation output from the band limiting circuit 20 to control the distance between the optical head 16 and the glass master 17 to be constant. Gap control device 2
1 is provided.

Hereinafter, the operation of the exposure apparatus according to this embodiment will be described along the flow of laser light or signals.

In the exposure apparatus, when recording a signal on the glass master 17 as an object to be exposed, first, a recording laser beam LB1 is emitted from the laser element 4, and the recording laser beam LB1 is electrically -Optical conversion element (EOM)
5. The light enters the acousto-optic device (AOM) 3 via an analyzer 6 as a polarizing plate and a beam splitter (BS) 7. The recording laser beam LB1 is modulated by the AOM3. Specifically, the information from the information source 1 is digitized by the recording signal generator 2 and input to the AOM 3, and the AOM 3 responds to the digitized information recording signal to input the recording information. The laser beam LB1 is modulated.

The recording laser beam LB1 modulated by the AOM 3 is reflected by the first mirror 10a, becomes a parallel beam by passing through the first condenser lens 11a and the collimator lens 12, and becomes a polarization beam splitter (PBS). 13 and enters the λ / 4 plate 14.

On the λ / 4 plate 14, the incident recording laser light LB 1 is circularly polarized, and the recording laser light LB 1, which is a circularly polarized modulated light, is reflected by the second mirror 10 b and is transmitted to the optical head 16. Incident. This optical head 16
Irradiates a circularly polarized recording laser beam LB1 onto the glass master 17 coated with a resist in a spot shape. Specifically, the recording laser light LB1 that has entered the second lens group that forms the optical head 16 is collected by the condenser lens 16a and then enters the SIL 16b. When the SIL 16b approaches the glass master 17 at a distance at which near-field light is generated (about 以下 or less of the wavelength of light), evanescent coupling occurs,
Recording laser beam LB totally reflected in SIL 16b
A part of 1 oozes out to the glass master 17 as near-field light,
The light enters the glass master 17 from the SIL 16b. By using this near-field light, it becomes possible to record a signal on the glass master 17 with the condensing spot diameter further reduced.

Here, the gap of the optical head 16 with respect to the glass master 17 is controlled by the gap control device 21 so that the distance between the glass master 17 and the optical head 16 is kept constant. This makes it possible to form a condensed spot whose diameter is controlled to be constant on the glass master 17 coated with the resist by the recording laser beam LB1 incident on the optical head 16. By using the light-converged spot having a certain size, the information source 1
The glass master 17 coated with the resist is cut in accordance with the recorded information.

As described above, in the exposure apparatus according to the present embodiment, the gap between the glass master 17 and the optical head 16 is controlled to perform the cutting of the glass master 17. The processing is performed as follows.

First, a part of the recording laser beam LB1 emitted from the laser element 4 used for recording, passed through the EOM 5 and the analyzer 6, and passed through the beam splitter 7
Is detected by the first photodetector (PD1) 8a.

The recording laser beam LB1 incident on the first photodetector (PD1) 8a is converted into an electric signal, and the output voltage is input to an automatic power controller (APC) 9. The difference between the output voltage and the reference voltage is EOM
5 is fed back to the applied voltage of
The laser power of the recording laser beam LB1 output from is controlled to be constant.

On the other hand, the light totally reflected in the SIL 16b of the optical head 16 without entering the glass master 17 as near-field light and the light incident on the glass master 17 as near-field light and entering the surface of the glass master 17 Reflected by the optical head 16
Is returned as the return light LB2 from the optical head 16 to the recording laser light LB1 as the second mirror 1
The light is reflected at 0b, passes through the λ / 4 plate 14, and is converted into linearly polarized light. The linearly polarized return light LB2 is reflected on the reflection surface of the polarization beam splitter 13, and
The second condensing lens 1 is reflected by the third mirror 10c.
1b. The light amount (return light amount S1) of the return light LB2 that has passed through the second condenser lens 11b is detected by a second photodetector (PD2) 8b that is a return light amount detection unit. The return light amount (signal) S1 detected by the second photodetector 8b is output to the band limiting circuit 2
Input to 0.

The band limiting circuit 20 to which the return light amount S1 is input limits the return light amount S1 to a band and outputs the return light amount S2 after the band limitation. The configuration and operation of the band limiting circuit 20 will be described later.

The return light amount S2 after the band limitation is input to the gap control device 21. The gap control device 21 outputs a gap control voltage S3 based on the information, using a reference signal generated by, for example, an internal constant voltage source as a control target value and a band-limited return light amount S2 as a controlled amount. . Then, the gap control voltage S3 is
Is input to

The optical head 16 is attached to the piezo element 15, and the expansion and contraction of the piezo element 15 is controlled according to the gap control voltage S3.
The distance between the glass master 17 is controlled. The piezo element 15 can convert an electric signal into a position displacement on a nano order.

FIG. 2 shows the return light amount S1 from the optical head 16.
4 shows a relationship between the control voltage of the piezo element 15 and the control voltage (PZT voltage). As shown in FIG. 2, while the control voltage of the piezo element 15 is small (the distance between the optical head 16 and the glass master 17 is long), no near-field light is generated and the optical head 1
The recording laser beam LB1 incident on the SIL 16b of No. 6 at an angle equal to or greater than the angle at which total reflection occurs is totally reflected within the SIL 16b and does not pass through the end face of the SIL 16b, so that the returning light amount S1 is constant.

However, as the control voltage of the piezo element 15 increases (the distance between the optical head 16 and the glass master 17 decreases), the return light amount S1 decreases. Specifically, when the control voltage of the piezo element 15 is increased, the piezo element 15 is extended, and the optical head 16 approaches the glass master 17. When the distance between the optical head 16 and the glass master 17 is equal to or less than の of the wavelength λ of light, the end face of the SIL 16 b of the optical head 16 is
7 is located in the near field region (near field region). For this reason, so-called seepage of near-field light from the end face of the SIL 16b to the glass master 17 is generated, that is, evanescent coupling occurs, light is transmitted to the glass master 17, and the return light amount S1 is reduced. Further, the piezo element 15
When the control voltage is increased, all the light incident on the SIL 16b passes through the glass master disk 17, so that the return light amount S1 eventually becomes zero.

The return light amount S1 and the piezo element 15
Has a linear relationship with the control voltage (PZT voltage) in the region where the above-mentioned evanescent coupling occurs. In the gap control according to the present embodiment, the return light amount S1 fixed in this region is controlled. The target value is set. Then, the gap control voltage S3 is determined so as to be drawn into the control target value of the return light amount S1 set in the region where the evanescent coupling occurs, and the piezo element 15 is controlled based on the determined value of the gap control voltage S3. Controls expansion and contraction. Thereby, the distance between the optical head 16 and the glass master 17 is made constant.

By the way, the optical head 16 and the glass master 17
In the gap control with the above, if the amount of light S1 returned from the optical head 16 is affected by the surface roughness of the glass master 17 and the resonance of the apparatus or the influence of modulation, the following problem occurs. Was.

FIG. 3A shows the return light amount S1 from the optical head 16 when the recording laser beam LB1 is not modulated by the information source 1 and the gap control is turned off. Thus, when the gap control is off,
The return light amount S1 fluctuates at a sufficiently low frequency with respect to the control band of several kHz due to dust and scratches on the glass master 17 and surface deviation of the glass master 17 itself. Further, the fluctuation of the frequency close to the control band is superimposed on this fluctuation due to the surface roughness of the glass master 17 and the resonance of the exposure apparatus.

FIG. 3B shows the return light amount S1 from the optical head 16 when the recording laser beam LB1 is modulated by the information source 1 and the gap control is turned off. Thus, when modulating the recording laser beam LB1,
The return light amount S1 is a signal in which the influence of the modulation signal is superimposed on the signal shown in FIG.

FIG. 4 (a) shows the signal of FIG. 3 (b) in which the return light amount S1 is signal-corrected so as to eliminate the influence of modulation without particularly limiting the frequency band. When the return light amount S1 is signal-corrected in this way, although the influence of the modulation of several MHz can be removed, since the frequency band is not particularly limited, the frequency of the glass master 17 which is a frequency close to the control band at several kHz is reduced. The effects of surface roughness and resonance of the exposure apparatus cannot be eliminated. Therefore, even when the gap control is performed by correcting the returning light amount S1 without particularly limiting the frequency band, the gap control performance is deteriorated and the quality of the recording signal is deteriorated.

Therefore, in the gap control according to the present embodiment, as shown in FIG. 4B, the return light amount S1 is band-limited so as to have a frequency sufficiently lower than the control band, and Eliminates the effects of surface roughness and exposure apparatus resonance. In this way, stable gap control can be performed without being affected by modulation of the recording signal, surface roughness of the glass master 17, resonance of the exposure apparatus, and the like, and deterioration of the quality of the recording signal can be prevented. Can be.

Next, the band limiting circuit 20 for limiting the frequency of the returning light amount S1 from the optical head 16 will be described. FIG. 5 shows a configuration of the band limiting circuit 20. The band limiting circuit 20 includes a binarizing circuit 22, sample holders (S / H) 23a, 23
b, 23c and 23d, and the first 5T pit detector 24
a, a second 5T pit detector 24b, a first 5T land detector 25a, and a second 5T land detector 25b.
And an averaging circuit 26. The band limiting circuit 20 limits the frequency band of the input return light amount S1, thereby controlling the influence of the modulation of the recording laser beam LB1 by the information source 1, the surface roughness of the glass master 17, the resonance of the exposure device, and the like. , The return light amount S2 after the band limitation (after the lowering of the band), which is not affected by the above, can be output.

FIG. 6 is a timing chart for explaining the operation of sampling and holding the return light amount S1 from the optical head 16 by the sampling holders 23a and 23b of the band limiting circuit 20. The return light amount S1 is discretized by the band limiting circuit 20, and the discrete point is held. Hereinafter, with reference to FIG. 5 and FIG.
8-16 modulation used in the recording laser beam LB
The operation of the band limiting circuit 20 when used for the modulation of 1 will be described.

The band limiting circuit 20 includes a return light amount S1 from the optical head 16 affected by the modulation of the recording signal, the state of the disk surface of the glass master 17 and the resonance of the exposure device.
Is entered. The return light amount S1 from the optical head 16 is 2
The data is input to the value conversion circuit 22 and digitized. The binarization circuit 22 can be realized by, for example, a comparator. The band limiting circuit 20 outputs the binarized return light amount S
Based on the 1 digital data, a pit portion of 10T or more and a land portion of 10T or more are detected, and a return light amount S1 at that time is sampled.

More specifically, first, a pit having a length of 5T is detected by the first 5T pit detection section 24a based on the binarized return light amount S1, and the pit having a length of 5T from the rising edge is detected. Is sampled and held by the sample holder 23a. And then,
When the second 5T pit detecting section 24b at the subsequent stage detects that the pit having the length of 5T detected by the first 5T pit detecting section 24a further has the length of 5T, the sample holder is used. At 23b, the sample hold value is updated. For example, as shown in FIG. 6, the pit portions of 10T, 6T and 11T all have a length of 5T.
The return light amount S1 detected by the first 5T pit detection unit 24a and located at a position 5T from the rising edge is sampled and held by the sample holder 23a. Then, only the 10T and 11T pit portions having a length of 5T are detected by the second 5T pit detection unit 24b, and the sample hold value is updated in the sample holder 23b.

The above operation makes it possible to sample and hold the return light amount S1 at the center of the pit portion of 10T or more with stability. That is, in the return light amount S1 input to the band limiting circuit 20, the return light amount S1 of the pit portion of 10T or more is sampled. Such 10T
By using the first 5T land detecting section 25a, the second 5T land detecting section 25b, and the sample holders 23c and 23d in the same manner as in the case of the pit section described above, 1
The return light amount S1 at the stable central portion of the land portion of 0T or more is sampled and held.

Then, the sampled and held return light amount S1 at the center of the pit portion of 10T or more and the sampled and returned light amount S at the center of the land portion of 10T or more.
1 is averaged by the averaging circuit 26 and output as the return light amount S2 after the band limitation. Thereafter, as described above, the return light amount S2 after the band limitation is set to the gap control device 2
1, the gap control that keeps the distance between the optical head 16 and the glass master 17 constant is performed by the gap control voltage S3 output from the gap control device 21.

In this embodiment, since the return light amount S2 after the band limitation is a sampling average value of the return light amount S1 of the pit portion and the land portion of 10T or more, the influence of the modulation on the return light amount S1 is reduced. Not only can it be removed, but also high-frequency fluctuations caused by the surface roughness of the glass master 17 and the resonance of the device as shown in FIG. 3A can be converted into signals within the gap control band. For example, 1-2
The frequency band of the light amount S1 can be limited to 500 Hz or lower with respect to the gap control band of KHz. For this reason, the problem that the follow-up error of the gap control increases and the quality of the recording signal deteriorates due to the fluctuation of the high frequency due to the surface roughness of the glass master 17 or the resonance of the apparatus is solved.

Further, in this embodiment, since the return light amount S1 at the stable central portion of the pit portion of 10T or more and the land portion of 10T or more is sampled and held, stable gap control can be performed. .

Further, in this embodiment, the sample holders 23a and 23a are used to limit the frequency band of the returning light amount S1 from the optical head 16 without using a low-pass filter.
Since the control is performed by b, 23c, and 23d, the return light amount S1 from the optical head 16 can be corrected to a sufficiently low frequency within the gap control band without deteriorating the stability of the gap control.

Furthermore, in this embodiment, low-cost and highly reliable gap control can be realized with only one recording laser LB1 and without changing the optical system.

[Second Embodiment] FIG. 7 shows a second embodiment of the present invention.
1 illustrates a configuration of an optical disc device that is a signal reproducing device according to an embodiment of the present invention. This optical disk device is used to reproduce a signal from an optical disk 30 which is an optical recording medium. In the optical disk device according to the present embodiment, the same components as those of the exposure apparatus according to the first embodiment are denoted by the same reference numerals, and the description of the first embodiment is referred to. Only the points different from the above embodiment will be described.

In this optical disk device, the optical disk 30
At the time of reproduction, the reproduction laser beam LB3 is incident on the optical head 16 without being modulated. The optical head 16 has an SIL1 on the signal recording surface of the optical disc 30.
The reproduction laser beam LB3 is applied in the form of a spot as near-field light oozing out from the end face of 6b. By utilizing this near-field light, it becomes possible to reproduce the signal from the optical disc 30 while further minimizing the focused spot diameter.

On the other hand, the light totally reflected in the SIL 16b of the optical head 16 without being incident on the optical disk 30 as near-field light and the incident light on the optical disk 30 as near-field light are modulated by the information signal of the optical disk 30. Being
The light reflected by the signal recording surface of the optical disk 30 and returned to the optical head 16 is returned as the return light LB4 from the optical head 16 to the reproduction laser beam LB3 by the second mirror 10
b, and is converted to linearly polarized light through the λ / 4 plate 14. The linearly polarized return light LB4 from the optical disk 16 is reflected by the reflection surface of the polarization beam splitter 13, and further reflected by the third mirror 10c.
The light is incident on the beam splitter 7b. By this beam splitter 7b, return light LB4 from the optical disk 16 is output.
Is returned light LB5 collected by the second condenser lens 11b and incident on the second photodetector (PD2) 8b.
Is reflected by the fourth mirror 10d, is collected by the third condenser lens 11c, and is condensed by the third photodetector (PD).
3) It is separated into return light LB6 incident on 8c.

Then, in the second photodetector 8b, the light amount (return light amount S1) of the incident return light LB5 is detected, and the detected return light amount (signal) S1 is input to the band limiting circuit 20. Further, in the third photodetector 8c, the light amount of the incident return light LB6 is detected, and the detected return light amount of the return light LB6 is input to the signal reproduction processing unit 31. The signal reproduction processing unit 31 performs a process of reproducing a signal from the optical recording medium.
The return light LB4 from the optical disk 16 is detected by a photodetector via a condenser lens without being separated by the beam splitter 7b, the detected electric signal is branched, and the branched electric signal is subjected to a band limiting circuit. 20
May be input to the signal reproduction processing unit 31.

In the band limiting circuit 20, the effect of the modulation of the reproduced signal (the effect of the presence or absence of pits) is obtained by limiting the frequency band of the input return light amount S1 by the same operation as in the first embodiment. Also, it is possible to output the return light amount S2 after band limitation (after lowering the band), which is not affected by the signal recording surface of the optical disk 30 and the resonance of the optical disk device.

FIG. 8 shows the sampling holder 23 of the band limiting circuit 20 of the optical disk device according to the present embodiment.
6 is a timing chart for explaining an operation of sampling and holding the return light amount S1 from the optical head 16 by using a and 23b. In the reproducing system as in the present embodiment, since the intersymbol interference occurs, the waveform of the returning light amount S1 becomes blunt.
However, similarly to the first embodiment, for example, 10T
Return light amount S of the above pit portion and land portion of 10T or more
If the stable central portion of 1 is sampled, the influence of intersymbol interference is eliminated. The operation of sampling and holding the return light amount S1 is the same as in the first embodiment.

Then, the return light amount S2 after such band limitation is input to the gap control device 21 and is determined by the gap control voltage S3 output from the gap control device 21.
Stable gap control for keeping the distance between the optical head 16 and the optical disk 30 constant is performed. As a result, the problem that the quality of the reproduced signal deteriorates is solved.

As described above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and can be variously modified.

For example, in each of the above embodiments, an example has been described in which the amount of return light S1 is affected by the modulation. However, the present invention can be applied to the case where the amount of return light S1 is not affected by the modulation. . The case where the return light amount S1 is not affected by the modulation is, for example, the case where a groove is recorded on a glass master by an exposure device which is a signal recording device, or the mirror surface of an optical disk is reproduced by an optical disk device which is a signal reproduction device. Is the case. Note that FIG.
As shown in (a), even when the return light amount S1 is not affected by the modulation, the return light amount S1 is affected by the surface roughness of the glass master and the optical disk and the resonance of the device, and is several KHz close to the control band.
Fluctuates.

FIG. 9 shows the configuration of the band limiting circuit 20 when the return light amount S1 is not affected by the modulation.
FIG. 10 is a timing chart for explaining the operation of sampling and holding the return light amount S1 by the sampling holder (S / H) 23e of the band limiting circuit 20. The band limiting circuit 20 receives a return light amount S1 affected by surface roughness of a glass master or the like and resonance of the apparatus. Then, the return light amount S1 is sampled and held by the sample holder 23e using a clock having an arbitrary frequency lower than the gap control band. Thereby, the return light amount S1
Is subjected to band limitation lower than the gap control band, and is output from the band limitation circuit 20 as the return light amount S2 after the band limitation (after the band reduction). Therefore, the return light amount S1
With respect to the above, a change in high frequency due to the surface roughness of the glass master 17 or the like and resonance of the device can be converted into a signal within the gap control band. Therefore, it is possible to solve the problem that the follow-up error of the gap control is increased and the quality of the recording signal is deteriorated due to the variation of the high frequency due to the surface roughness of the glass master 17 and the resonance of the apparatus.

In the first embodiment, an example is described in which the signal recording device is an exposure device. However, the signal recording device can be applied to an optical disk device that records signals on an optical disk.

Furthermore, in each of the above embodiments, an example has been described in which the return light amount S1 of the pit portion of 10T or more and the land portion of 10T or more is sampled and held. The amount of return light S1 of the pit portion and the land portion of 10T or more may be sampled and held.

Furthermore, in each of the above embodiments, an example has been described in which the return light amount S1 of the pit portion of 10T or more and the land portion of 10T or more is sampled and held. And the return light amount S1 of only one of the land portions of 10T or more may be sampled and held. This eliminates the need for an averaging circuit.

In each of the above embodiments, the optical head 1
Although the example using the condenser lens 16a and the SIL 16b as the optical means of the sixth embodiment has been described, the SIM (Solid Immersion
Mirror), and optical means composed of three or more groups, including SIL and SIM,
It is sufficient that the light is incident on the end face at an angle equal to or greater than the angle at which total reflection light is generated.

[0062]

As described above, according to the present invention,
When performing recording or reproduction on an optical recording medium using near-field light, not only is it not affected by the modulation of the recording or reproduction signal, but also the surface roughness of the signal recording surface of the optical recording medium and the influence of resonance of the device, etc. Based on the amount of return light converted to a signal
Since gap control of the distance between the optical means and the optical recording medium can be performed, stable gap control can be performed so that the distance between the optical means and the optical recording medium is constant. Alternatively, the quality of a reproduced signal can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an exposure apparatus that is a signal recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a control voltage of a piezo element and a return light amount.

FIG. 3 (a) shows that a recording laser beam is not modulated,
FIG. 3B is a diagram illustrating a signal waveform of a return light amount when the gap control is turned off. FIG. 3B illustrates a return light amount when the recording laser light is modulated and the gap control is turned off. FIG. 4 is a diagram showing a signal waveform of FIG.

FIG. 4A is a diagram showing a signal waveform of a return light amount when correction is performed by removing only the influence of modulation without limiting the frequency band, and FIG. FIG. 7 is a diagram illustrating a signal waveform of a return light amount when the frequency band is limited according to the embodiment.

FIG. 5 is a block diagram showing a configuration of a band limiting circuit provided in the exposure apparatus shown in FIG. 1;

FIG. 6 is a timing chart showing an operation of sampling and holding a return light amount by the band limiting circuit shown in FIG. 5;

FIG. 7 is a block diagram illustrating a configuration of an optical disc device that is a signal reproducing device according to a second embodiment of the present invention.

8 is a timing chart showing an operation of sampling and holding a return light amount by a band limiting circuit provided in the optical disk device shown in FIG. 7;

FIG. 9 is a block diagram illustrating a configuration of a band limiting circuit when the amount of return light is not affected by modulation.

10 is a timing chart showing an operation of sampling and holding the return light amount by the band limiting circuit shown in FIG. 9;

[Explanation of symbols]

1 information source, 2 recording signal generator, 3 AOM, 4 laser element, 5 EOM, 6 analyzer, 7 B
S, 8a PD1, 8b PD2, 8c PD3, 9 ...
APC, 10a, 10b, 10c, 10d: mirror, 1
1a, 11b, 11c: condenser lens, 12: collimator lens, 13: PBS, 14: λ / 4 plate, 15: piezo element, 16: optical head, 16a: condenser lens, 16b
... SIL, 17 ... glass master, 20 ... band limiting circuit,
21: gap control device, 22: binarization circuit, 23a,
23b, 23c, 23d, 23e ... sample holder,
24a, 24b... 5T pit detector, 25a, 25b.
5T land detection unit, 26 averaging circuit, 30 optical disk, 31 signal reproduction processing unit, LB1 recording laser light, LB2 return light, LB3 reproduction laser light, LB
4, LB5, LB6 ... return light, S1 ... return light amount, S2 ...
Return light amount after band limitation, S3: gap control voltage

Continued on the front page F-term (reference) 5D090 AA01 BB01 BB02 BB03 BB04 CC01 CC04 FF05 FF11 5D118 AA13 BA01 BB01 BB02 BB09 BF02 BF03 CA04 CA11 CA26 CD02 5D119 AA11 AA22 AA29 BA01 BB01 BB02 BB04 BB09 BB04

Claims (12)

[Claims] 1. A signal recording apparatus for recording a signal on an optical recording medium using near-field light, comprising: a light source for emitting a laser beam; and a light source disposed in close proximity to a signal recording surface of the optical recording medium. The emitted laser light is incident, optical means for condensing near-field light by the laser light on the optical recording medium, return light amount detecting means for detecting the amount of return light from the optical means and the optical recording medium, Return light amount correction means for correcting the return light amount to a signal having a limited frequency band; gap control for controlling a distance between the optical unit and the optical recording medium according to the return light amount corrected by the return light amount correction means And a signal recording device. 2. The return light amount correction means discretizes the return light amount detected by the return light amount detection means and holds the discrete point to control the frequency band of the return light amount by the gap control means. 2. The signal recording apparatus according to claim 1, wherein the signal is corrected to an amount limited within a band. 3. The optical device according to claim 1, wherein the optical unit is a solid immersion device (SIL).
2. The signal recording device according to claim 1, wherein the signal recording device is configured to include: 4. The optical means includes a SIM (Solid Immersi
2. The signal recording device according to claim 1, wherein the signal recording device is configured to include (on Mirror). 5. A signal recording method for recording a signal on an optical recording medium by using near-field light, wherein the laser light emitted from a light source is arranged in proximity to a signal recording surface of the optical recording medium. The optical means converges near-field light by the laser light on the optical recording medium, detects the amount of return light from the optical means and the optical recording medium, and limits the frequency band of the detected amount of return light. To the corrected signal, and according to the return light amount corrected by limiting this frequency band,
A signal recording method comprising controlling a distance between the optical unit and the optical recording medium. 6. The detected return light amount is discretized, and the discrete point is held, thereby limiting the frequency band of the return light amount to a control band of a distance between the optical unit and the optical recording medium. 6. The signal recording method according to claim 5, wherein the amount is corrected to an amount. 7. A signal reproducing apparatus for reproducing a signal from an optical recording medium using near-field light, comprising: a light source for emitting a laser beam; and a light source disposed in close proximity to a signal recording surface of the optical recording medium. A laser beam emitted from the laser beam is incident thereon, an optical unit that focuses near-field light by the laser beam on the optical recording medium, and a return light amount detection unit that detects a return light amount from the optical unit and the optical recording medium. A return light amount correction unit that corrects the return light amount to a signal whose frequency band is limited; and a gap that controls a distance between the optical unit and the optical recording medium according to the return light amount corrected by the return light amount correction unit. A signal reproducing device comprising a control unit. 8. The return light quantity correction means discretizes the return light quantity detected by the return light quantity detection means, and holds the discrete point, thereby controlling the frequency band of the return light quantity by the gap control means. 8. The signal reproducing apparatus according to claim 7, wherein the signal is corrected to an amount limited within a band. 9. The optical device according to claim 8, wherein the optical unit is a solid immersion system (SIL).
8. The signal reproducing apparatus according to claim 7, wherein the signal reproducing apparatus is configured to include on-lens. 10. The optical means is a SIM (Solid Immer).
8. The signal reproducing apparatus according to claim 7, wherein the signal reproducing apparatus is configured to include a sion mirror. 11. A signal reproducing method for reproducing a signal from an optical recording medium using near-field light, wherein the laser light emitted from a light source is arranged in proximity to a signal recording surface of the optical recording medium, The optical means is focused on the near-field light by the laser light on the optical recording medium, the amount of return light from the optical means and the optical recording medium is detected, and the detected return light amount is converted into a frequency band. Corrected to the limited signal, and according to the amount of return light corrected by limiting this frequency band,
A signal reproducing method comprising controlling a distance between the optical unit and the optical recording medium. 12. The detected return light amount is discretized,
12. The signal according to claim 11, wherein by holding the discrete points, the frequency band of the return light amount is corrected to an amount limited within a control band of a distance between the optical unit and the optical recording medium. Playback method.