JPH11203692A - Optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a track servo offset caused by variations in track error signal occurring when scanning defects existing in an information recording medium, in a case of being provided with a track control mechanism. SOLUTION: A light flux emitted from a semiconductor laser 1 is focused on an optical disk 7 and the reflected light is received by a photo-detector 10 for reproducing and error signal, and each error signal of the reproducing signal, focus, and track is detected, and at least a track control for the optical disk is performed. Moreover, a light flux for detecting defects off the viewing angle of a collimator lens 3 is guided to an optical disk 7 by a 1st turning back mirror 11, and is focused at a more advanced position in the rotational direction of the optical disk 7 than the focal spots SP1-SP3 of the above- mentioned emitted light flux, and this reflected light of the light flux for defect detection is received by the 1st defect detection photo-detector 12, and thus, the defect is detected from a change in the level of the received light. When the defect is detected, the track control is halted for a predetermined time to make the objective lens 6 of the optical head into a fixed state and prevent a track offset from occurring by the defect, and thus, a track servo displacement is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for recording / reproducing information on / from an information recording medium such as an optical disk, and more particularly to an optical head which is caused by defects such as scratches and dirt present on the information recording medium. The present invention relates to an optical head that prevents track deviation and a track control method therefor.

[0002]

2. Description of the Related Art In the field of multimedia in recent years, optical disks capable of recording and reproducing information using optical technology have been remarkably developed, and ROMs such as DVDs and CDs have been particularly developed.
Expectations have been raised for optical disks and write-once optical disks such as CD-Rs. However, this type of information recording medium records and reproduces information by using the reflection and transmission of light applied to the information recording medium, so that the surface of the information recording medium has defects such as scratches and dirt. This results in a recording or reproduction error as it is. In particular, most of the above-mentioned optical discs are not contained in a protective cartridge. Therefore, if the optical disc is not handled carefully, the surface of the optical disc will be scratched, fingerprints, etc., causing defects. Due to this defect, a large offset occurs in a track error signal used for controlling the track of the optical head with respect to the optical disk, and the track servo is deviated, so that the recording / reproduction of suitable information can be performed.
Reproduction becomes difficult. In particular, such a problem is remarkable in an information recording medium having large eccentricity.

FIG. 5A is a configuration diagram of an optical system showing an example of a conventional optical head for a CD. The light beam LB emitted from the semiconductor laser 1 is divided into three light beams LB1 to LB3 by the diffraction grating 2.
Divided into Depending on the arrangement of the semiconductor laser 1, the light flux L
Since B is P-polarized light (y-axis direction in the figure), it passes through the polarizing beam splitter 4 and becomes parallel light by the collimator lens 3. Thereafter, the light is converted into circularly polarized light by the 波長 wavelength plate 5 and is condensed on the recording surface of the optical disk 7 by the objective lens 6 to form three condensed spots SP1 to SP3 on the recording surface. On the optical disk 7, the condensed spots SP1 to SP3 are reflected, enter the objective lens 6 again, and return to parallel light. This parallel light is converted into S-polarized light (z-axis direction in the figure) by the quarter-wave plate 5, and
The light is condensed again by the collimator lens 3. Then, the light is reflected by the polarization beam splitter 4, passes through the cylindrical lens 9, and is guided to the reproduction / error signal photodetector 10.

FIG. 5 (b) shows a configuration diagram of a photodetector of the photodetector 10 for reproducing / error signal. The refocused spot RSP2 at the center corresponding to the three focused spots SP1 to SP3, and the upper and lower focused spots RSP1 and RSP3 are incident on the focus error photodetector 10a and the track error photodetectors 10b and 10c, respectively. Is done. Then, a reproduction signal is obtained by utilizing a part of each of the refocused spots RSP1 to RSP3, and a focus error light detecting element 10a that receives the refocused spot RSP2.
Focus control by the so-called astigmatism method for controlling the focus position of the optical head with respect to the optical disk 7 based on the focus error signal obtained from the comparison of the received light intensity on each of the divided light receiving surfaces is performed. Further, each of the refocused spots R
Each of the photodetectors 10b for receiving SP1 and RSP3,
Track control is performed by a so-called three-beam method for controlling the track position of the optical head with respect to the optical disk 7 based on the track error signal obtained from the received light intensity of 10c.

[0005]

In this type of optical head, if the surface of the optical disk 7 has a defect such as a scratch or dirt as described above, the light from the optical head is defective when recording / reproducing information. When scanning is performed and the above-described control is performed by receiving the reflected light from the defect, the track error signal using the three beams is disturbed, and a large track offset is generated to deviate the track servo. Problems arise. For example, suppose that a scratch X in the z-axis direction (radial direction of the optical disc) exists on the surface of the optical disc 7 as shown in FIG. When the three condensed spots SP1 to SP3 of the optical head pass through the flaw X, the light detecting elements 10a to 10a-1
The refocused spots RSP1 to RSP3 on 0c are shown in FIG.
As shown in (b), the pattern extends in the y-axis direction on the optical disk 7 surface, in other words, in the x-axis direction on the light receiving surface of the photodetector 10. This is a light spot SP1 to SP
3 is diffracted, and the elongation of the pattern in the x-axis direction is the diffracted light due to the flaw X. The diffracted light wraps around to the adjacent photodetectors 10a, 10b, and 10c, and the position of the flaw X and the condensed spots SP1 to SP3 causes the photodetector 1 to move.
The amount of light circulating between 0a to 10c is unbalanced.

Normally, in the three-beam method used for the track error signal detection method, the light intensity of the central light beam is set to be higher than the light intensity of the upper and lower light beams. Therefore, the refocused spot R
The diffracted light of SP2 is used as the tracking error photodetector 10b, 1
The amount of wraparound to 0c is the refocused spot RSP1, RSP3
Is not negligible for the light intensity of Therefore, an offset occurs in the track error signal. In this case, if the distance between the light detecting elements in the x direction is widened, it is possible to reduce the divergence of the diffracted light to the track light detecting element, but it is necessary to widen the distance between the three beams on the recording surface of the optical disk. In this case, since the track servo characteristics with respect to the eccentricity of the optical disk are deteriorated, there is a limit to widening the interval between the photodetectors.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical head and a track control method in which a track servo does not deviate even when a defect existing on an optical disk is scanned.

[0008]

An optical head according to the present invention converges a light beam emitted from a light source onto a recording track of an information recording medium and receives a reflected light beam from the information recording medium to generate at least a track error signal. And a track control system for controlling the focusing position of the emitted light beam based on the track error signal, wherein the position before the emitted light beam is focused on the information recording medium Converging a light beam for a defect on the recording track, receiving a reflected light beam of the light beam for the defect, and fixing the control of the track control system for a predetermined time according to a light receiving level of the reflected light beam for the defect. Means for setting a state. The means for fixing the track control system includes: means for condensing a light beam for a second defect at a position at a time point after the emitted light beam is converged on the information recording medium; Means for releasing the fixed state of the control of the track control system in accordance with the light receiving level of the reflected light beam for the second defect focused on the position.

Further, in the track control method for an optical head according to the present invention, a light beam emitted from a light source is condensed on a recording track of an information recording medium, and a light beam reflected from the information recording medium is received to at least track error signal. And a track control system for controlling the focusing position of the emitted light beam based on the track error signal, wherein the position before the emitted light beam is focused on the information recording medium A light beam for a defect is condensed, and a reflected light beam of the light beam for the defect is received, and the control of the track control system is fixed for a predetermined time according to a light receiving level of the reflected light beam for the defect. It is characterized by. Alternatively, the first defect light beam is focused at a position before the emitted light beam is focused on the information recording medium, and the second defect light beam is focused at a later time position, And receiving the reflected light beams of the first and second defect light beams, setting the control of the track control system in a fixed state in accordance with the light receiving level of the first defect reflected light beam, and The fixed state of the control of the track control system may be released according to the light receiving level of the reflected light beam for use.

In the present invention, at least a focus spot for defect detection is arranged before a focus spot for obtaining a track error signal, and the track control is fixed by the focus spot for defect inspection, thereby obtaining information. If there is a defect in the recording medium, the focus spot for defect detection detects the defect before the focus spot for the track error signal scans the defect, and the track control is fixed and the position is set to that position. The objective lens is fixed to prevent track offset. Further, by arranging a focused spot for defect detection after a focused spot for obtaining a track error signal, the completion of scanning of a defect can be detected, and the fixed state of the track control is released.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, and FIG. 1A is a configuration diagram of an optical system. The light beam LB emitted from the semiconductor laser 1 is divided by the diffraction grating 2 into three light beams LB1.
~ LB3. Depending on the arrangement of the semiconductor laser 1,
Since the light beam LB is P-polarized light (in the y-axis direction in the figure), the three light beams LB1 to LB3 pass through the polarization beam splitter 4 and become parallel light by the collimator lens 3.
Thereafter, the light is converted into circularly polarized light by the 板 wavelength plate 5 and the objective lens 6
The light is condensed on the recording surface of the optical disk 7 to form three condensed spots SP1 to SP3 on the recording surface. The condensed spots SP1 to SP3 are reflected by the optical disk 7, enter the objective lens 6 again, and return to parallel light. This parallel light is 1
The light is converted into S-polarized light (in the z-axis direction in the figure) by the 波長 wavelength plate 5 and is re-focused by the collimator lens 3. Then, the light is reflected by the polarization beam splitter 4, passes through the cylindrical lens 9, and is guided to the reproduction / error signal photodetector 10.

On the other hand, of the higher-order diffracted light diffracted by the diffraction grating 2, the fourth light beam LB4 which is out of the field of view of the collimator lens 3 is the three light beams LB1 to LB.
The light is reflected by the first folding mirror 11 disposed on one side of the collimator lens 3, and the 1 /
After passing through the four-wavelength plate 5, the light is condensed on the surface of the optical disk 7 by the objective lens 6, and is spotted on the optical disk 7.
4 are formed. Here, the spot SP4 is the spot S
The position and angle of the first folding mirror 11 are adjusted so as to be ahead of P1 to SP3 in the rotation direction of the optical disk. And the spot S
After passing through the objective lens 6, the reflected light of P4
The light is converted into S-polarized light by the wave plate 5, and is condensed again by the collimator lens 3. The S-polarized light beam LB4 is reflected by the polarization beam splitter 4, and collected by the cylindrical lens 9 on the first defect light detector 12 as a fourth refocused spot.

FIG. 1B is a plan layout view of the photodetector 10 for reproduction / error signal and the photodetector 12 for the first defect. The reproduction / error signal photodetector 10 has the same configuration as that of the prior art, and the central focus error photodetector 10
The focus control of the optical head is performed by the refocused spot RSP2 focused on a. Further, three refocused spots RSP1 to RSP1 which are respectively focused on the focus error light detecting element 10a and the track error light detecting elements 10b and 10c arranged on both sides in the x-axis direction.
By P3, track control of the optical head is performed by the three-beam method. And the reproduction / error signal photodetector 10
The light detecting element 12a of the first defect light detector 12 is disposed at a position adjacent to the z-axis direction, and the re-focused spot RSP4 of the fourth focusing spot SP4 is focused. Therefore, in the first defect photodetector 12, if the optical disk 7 has a defect, the condensed spot S
Diffraction occurs when P4 is condensed on the defect, the amount of light reflected in the optical axis direction is reduced, and the light receiving level of the refocused spot RSP4 at the first defect photodetector 12 is reduced. Become. Although not shown, the reproduction / error signal photodetector 10 and the defect photodetector 12 are electrically connected to a track control circuit (not shown), and a detection output from these photodetectors is provided. It is configured to perform track control of the optical head based on this.

The operation of track control by the optical head having this configuration will be described. FIG. 2 is a diagram showing a track error signal obtained from the reproduction / error signal photodetector 10 and an output signal of the first defect photodetector 12. Optical disk 7
With the rotation of the optical head, the four light beams from the optical head condense the condensed spots SP1 to SP4 on the optical disc 7 at positions shifted from each other in the rotation direction. Scans on the recording track of the optical disk 7 before the other focused spots. For this reason, when the condensing spot SP4 scans the defect, the level of the detection signal of the first defect photodetector 12 is reduced as between times t3 and t4 in FIG. For this reason, the condensed spot SP2 located behind the condensed spot SP4 in the rotation direction of the optical disc is moved to the next point in time t1.
When the defect is scanned from t to t2, the effect of diffraction due to the defect appears on the track error signal, causing a large track offset. Therefore, when the first defect photodetector 12 detects a defect, for example, from time t3 to time t2 when the condensed spot SP2 passes through the defect, the track control circuit outputs the signal from the first defect photodetector 12. The track control is stopped based on the detection signal. As a result, the objective lens 6 of the optical head is fixed in the radial direction (z-axis direction) of the optical disk 7 at the time t3 when the defect is detected, and the track offset due to the defect is prevented beforehand.

The time for stopping the track control from time t3 to time t2 is determined by measuring the time corresponding to the defect length detected by the second defect photodetector 12 from the time t3 to time t4. The time can be easily obtained by performing an operation of adding the time to a preset time difference between the converging spot SP4 and the converging spot SP2. In addition,
It is also possible to use the light spot SP1 or SP3 instead of the light spot SP2.

FIG. 3 is a diagram showing a second embodiment of the present invention. Note that parts equivalent to those in the first embodiment are denoted by the same reference numerals. In the second embodiment, as shown in FIG. 3A, two folding mirrors for reflecting high-order diffracted light diffracted by the diffraction grating 2 are arranged on both sides of the optical axis. I have. That is, the first folding mirror 1
The second folding mirror 13 is arranged at a position 180 degrees with respect to the optical axis 1 with respect to the optical axis, in other words, at a position where scanning is delayed along the rotation direction of the optical disk 7, and the light is diffracted by the diffraction grating 2. The higher-order fifth light beam LB5 is
The reflection mirror 13 is configured to reflect the light. With this configuration, the fifth light beam LB5 reflected by the second folding mirror 13 passes through the collimator lens 3, and
After being converted into circularly polarized light by the wavelength plate 5 and condensed by the objective lens 6, the condensed light becomes a condensed spot SP5 at a position delayed in the rotation direction of the optical disc 7. The luminous flux of the condensed spot SP5 reflected by the optical disk 7 passes through the objective lens 6, and then passes through the ４ wavelength plate 5
Is converted into S-polarized light, re-condensed by the collimator lens 3, and reflected by the polarization beam splitter 4. Thereafter, the light is incident on the second defect photodetector 148 through the cylindrical lens 9. The condensed spots SP1 to SP3 of the three outgoing light beams LB1 to LB3 diffracted by the diffraction grating 2 are reflected by the optical disk 7 and then re-condensed spots RSP
1 to RSP3 are detected by the reproduction / error signal photodetector 10, and the fourth condensed spot SP1 obtained by being reflected by the first folding mirror 11 is reflected by the optical disc 7, The refocused spot RSP4
Is detected by the first defect light detector 12 in the same manner as in the first embodiment.

FIG. 3B is a plan view of the reproduction / error signal photodetector 10, the first defect photodetector 12, and the second defect photodetector 14. The photodetectors 12a and 14a of the first defect photodetector 12 and the second defect photodetector 14 are arranged at both side positions adjacent to the reproduction / error signal photodetector 10 in the z-axis direction. And the fourth and fifth refocused spots RSP4 and RSP5 are focused. Therefore, if a defect occurs in the optical disk 7, diffraction occurs when the spots SP4 and SP5 are focused on the defect, and the amount of reflected light in the optical axis direction is reduced.
The light receiving levels at the defect photodetector 12 and the second defect photodetector 14 are reduced. As in the first embodiment, the reproduction / error signal photodetector 10 and the first and second defect photodetectors 12, 14 are electrically connected to a track control circuit (not shown). The optical head is configured to perform track control based on detection outputs from these photodetectors.

FIG. 4 shows the photodetector 10 for the reproduction / error signal.
Error Signal Obtained from Detector and First Defect Photodetector 1
FIG. 3 is a diagram showing output signals of the second and second defect photodetectors 14. Changes in the track error signal and the detection signal of the first defect photodetector 12 are the same as those in FIG. In addition to this, if the condensed spot SP5 of the fifth light beam LB5 scans for a defect and then scans for a defect on the surface of the optical disk 7 between times t5 and t6, the output signal is generated by diffraction at the defect. Decrease. Therefore,
From time t3 when the defect is detected by the first defect light detector 12 to time t6 when the defect is detected by the second defect light detector 14, the objective lens 6 of the optical head is moved in the z-axis direction. By controlling the position to be fixed at the time point t3, a track offset can be prevented.
In the second embodiment, since the end point of the time for fixing the objective lens 6 is determined based on the output of the second defect photodetector 14, the track control circuit has a defect as in the first embodiment. A measuring circuit and an arithmetic circuit for detecting time are not required, which simplifies the circuit configuration and enables application to an optical disk that rotates at high speed.

Here, in each of the above embodiments, the converging spots SP4 and SP5 for detecting a defect of the optical disk 7 are formed using the first and second folding mirrors 11 and 13, The traveling direction of the light beam may be changed in a region where the light beams LB4 and LB55 pass. For example, the light beams LB4 and LB5 are condensed into spots SP4 and SP5.
So that a spot can be formed at the same position as
Even if another diffraction grating is provided in the area where the light beams LB4 and LB5 pass, there is no practical problem. Further, the present invention is effective in both cases of recording and reproducing information on an information recording medium.

[0020]

As described above, according to the present invention, at least a focus spot for defect detection is arranged before a focus spot for obtaining a track error signal, and track control is fixed by the focus spot for defect inspection. By state
If there is a defect in the information recording medium, before the focused spot for the track error signal scans the defect, the focused spot for the defect detection detects the defect and the track control is fixed and the position is determined. , The objective lens is fixed, and track offset can be prevented. In addition, by arranging a focus spot for defect detection after a focus spot for obtaining a track error signal, the completion of scanning of a defect can be detected, and the fixed state of the track control is released without complicating the track control circuit. be able to.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical system and a plan view of a photodetector according to a first embodiment of the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation of the optical head having the configuration of FIG.

FIG. 3 is a configuration diagram of an optical system and a plan view of a photodetector according to a second embodiment of the present invention.

FIG. 4 is a signal waveform diagram for explaining the operation of the optical head having the configuration of FIG. 3;

FIG. 5 is a configuration diagram of an optical system as an example of a conventional optical head and a plan view of a photodetector.

FIG. 6 is a schematic diagram when a conventional optical head scans for a medium defect and a plan view of a photodetector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Diffraction grating 3 Collimator lens 4 Polarization beam splitter 5 1/4 wavelength plate 6 Objective lens 7 Optical disk 9 Cylindrical lens 10 Photodetector for reproduction / error signal 10a Photodetector for focus error 10b, 10c Light for track error Detecting element 11 First return mirror 12 First defect photodetector 13 Second return mirror 14 Second defect photodetector LB, LB1 to LB5 Light flux SP1 to SP5 Focus spot RSP1 to RSP5 Refocus spot

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[Procedure amendment]

[Submission date] February 22, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] light heads

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

3. An optical system for converging a light beam emitted from a light source onto a recording track of an information recording medium and receiving a reflected light beam from the information recording medium to obtain at least a track error signal; a tracking control system for controlling the condensing position of the emitted light beam on the basis of the track system
Fixing means for fixing the control system, wherein the optical system
Is a means for separating a light beam emitted from the light source into a plurality of light beams.
A step and the plurality of light beams are respectively reflected by the information recording medium.
A reproduction / error photodetector for receiving the emitted light beam
The track error is determined by the output of the read / error photodetector.
Fixed to the track control system so as to obtain a signal
The means for setting the state is separated by the means for separating the emitted light beam.
Light beam outside the field of view of the optical system
At the time before the emitted light beam is focused on the information recording medium.
At the position of the recording track as a light flux for defects
Focusing, and receiving the reflected light beam of the defect light beam,
The track according to the light receiving level of the reflected light beam for recording defects
An optical head , wherein control of a control system is fixed for a predetermined time .

Wherein means for the fixed mode the tracking control system comprises a means for second converging light flux for defect at the position of the point after the emitted light beam is focused on the information recording medium, wherein 4. The apparatus according to claim 3 , further comprising: means for releasing a fixed state of the control of the track control system in accordance with a light receiving level of the reflected light flux for the second defect condensed at a position at a later point in time. Light head.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for recording / reproducing information on / from an information recording medium such as an optical disk, and more particularly to an optical head which is caused by defects such as scratches and dirt present on the information recording medium. relates <br/> the optical head to prevent off-track that.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008]

Means for Solving the Problems The optical head of the present invention, light
Beam emitted from the source is focused on the recording track of the information recording medium
Receiving the reflected light beam from the information recording medium and resuming it.
Optical head with condensing optical system to obtain raw and error signals
Out of the field of view of the focusing optics with the luminous flux of the light source
An optical system for guiding the light beam on the side into the field of view,
The light beam on the outside is focused on the information recording medium to
It is characterized by detecting a defect of the recording medium. Also before
Guides light beams outside the field of view of the focusing optics into the field of view
The light beam for defect detection guided in the optical system is
.The emitted light beam for obtaining the error signal is collected on the information recording medium;
It is configured to focus before or before or after the light
From the information recording medium of the light beam for detecting the defect.
Of the information recording medium depending on the light receiving level of the reflected light flux
It is characterized by comprising means for detecting a fault.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

In a preferred embodiment of the present invention, a light source
Outgoing luminous flux on the recording track of the information recording medium
At least receiving the reflected light beam from the information recording medium.
An optical system for obtaining a track error signal;
A trajectory for controlling a condensing position of the emitted light beam based on a signal.
The track control system and the track control system in a fixed state.
The optical system includes light emitted from the light source.
Means for separating the bundle into a plurality of luminous fluxes;
To receive the light beams reflected by the information recording medium.
A raw / error photodetector, wherein the reproduction / error photodetection is performed.
Configured to obtain the track error signal at the output of the detector.
Means for fixing the track control system,
The light separated by one of the means for separating the emitted light flux
The outgoing light beam is a light beam outside the field of view of the science system.
Recording at a position before the light is focused on the information recording medium.
Focus on the track as a light beam for the defect, and
The reflected light beam of the light beam is received, and the reflected light beam for the defect is received.
The control of the track control system is performed for a predetermined time according to the light level.
Only fixed state. Also fixed the track control system
The means for setting the state is such that the emitted light beam is transmitted to the information recording medium.
At the position after the light is focused, the light flux for the second defect is
Means for collecting light, and the second
2 according to the light receiving level of the reflected light flux for the defect 2.
Means for releasing the fixed state of the control of the lock control system.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

On the other hand , the fourth light beam LB4 that is out of the field of view of the collimator lens 3 is the three light beams LB1.
LB3, reflected by the first folding mirror 11 disposed on one side, and transmitted through the collimator lens 3 and the quarter-wave plate 5, and then condensed on the surface of the optical disk 7 by the objective lens 6. As a result, a spot SP4 is formed on the optical disk 7. Here, the first folding mirror 1 is positioned such that the spot SP4 is located ahead of the spots SP1 to SP3 in the rotation direction of the optical disk.
The position and angle of 1 are adjusted. Then, the reflected light of the spot SP4 passes through the objective lens 6, and
The light is converted into S-polarized light by the 波長 wavelength plate 5, and the collimator lens 3
Is collected again. The S-polarized light beam LB4 is reflected by the polarization beam splitter 4, and collected by the cylindrical lens 9 on the first defect light detector 12 as a fourth refocused spot.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

FIG. 1B is a plan layout view of the photodetector 10 for reproduction / error signal and the photodetector 12 for the first defect. The reproduction / error signal photodetector 10 has the same configuration as that of the prior art, and the central focus error photodetector 10
The focus control of the optical head is performed by the refocused spot RSP2 focused on a. Further , the refocused spot RS focused on the focus error light detecting element 10a.
Light is condensed on P2 and the track error photodetectors 10b and 10c disposed on both sides in the x-axis direction.
Two re-condensing spot RSP1, RSP3 track control of the optical head by the three-beam method by is performed. The photodetector 12a of the first defect photodetector 12 is disposed at a position adjacent to the reproduction / error signal photodetector 10 in the z-axis direction.
The refocused spot RSP4 of P4 is focused. For this reason, in the first defect photodetector 12, when the optical disc 7 has a defect, when the condensed spot SP4 is condensed on the defect, diffraction occurs, and the reflected light amount in the optical axis direction. Is reduced, and the light receiving level of the refocused spot RSP4 in the first defect photodetector 12 is reduced. Although not shown, the reproduction / error signal photodetector 10 and the defect photodetector 12 are electrically connected to a track control circuit (not shown), and a detection output from these photodetectors is provided. It is configured to perform track control of the optical head based on this.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

FIG. 3 is a diagram showing a second embodiment of the present invention. Note that parts equivalent to those in the first embodiment are denoted by the same reference numerals. In the second embodiment, as shown in FIG. 3A, the collimator lens 3 is out of the field of view.
And two folding mirrors for reflecting light beams arranged on both sides of the optical axis. In other words, the second folding mirror 13 is arranged at a position 180 degrees with respect to the first folding mirror 11 with respect to the optical axis, in other words, at a position where the scanning is delayed along the rotation direction of the optical disk 7,
Fifth light flux L deviating from the field of view of collimator lens 3
B5 is configured to be reflected by the second folding mirror 13. With this configuration, the second folding mirror 13
After passing through the collimator lens 3, the fifth light beam LB 5 reflected by the light beam is converted into circularly polarized light by the 波長 wavelength plate 5,
After the light is condensed, the light becomes a condensed spot SP5 at a position delayed in the rotation direction of the optical disk 7. After passing through the objective lens 6, the luminous flux of the condensed spot SP5 reflected by the optical disc 7
The light is converted into S-polarized light by the 波長 wavelength plate 5, re-condensed by the collimator lens 3, and reflected by the polarization beam splitter 4. Thereafter, the light passes through a cylindrical lens 9 and passes through the second defect photodetector 1.
48. The converging spots SP1 to SP3 of the three outgoing light beams LB1 to LB3 diffracted by the diffraction grating 2
After the SP3 is reflected by the optical disk 7, the refocused spots RSP1 to RSP3 are detected by the reproduction / error signal photodetector 10, and the spots RSP1 to RSP3 obtained by the first return mirror 11 are reflected. 4 focused spots S
The fact that P1 is reflected by the optical disk 7 and the refocused spot RSP4 is detected by the first defect photodetector 12 is the same as in the first embodiment.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

FIG. 3B is a plan view of the reproduction / error signal photodetector 10, the first defect photodetector 12, and the second defect photodetector 14. The photodetectors 12a and 14a of the first defect photodetector 12 and the second defect photodetector 14 are arranged at both sides of the reproduction / error signal photodetector 10 adjacent to each other in the x- axis direction. And the fourth and fifth refocused spots RSP4 and RSP5 are focused. Therefore, if a defect occurs in the optical disk 7, diffraction occurs when the spots SP4 and SP5 are focused on the defect, and the amount of reflected light in the optical axis direction is reduced.
The light receiving levels at the defect photodetector 12 and the second defect photodetector 14 are reduced. As in the first embodiment, the reproduction / error signal photodetector 10 and the first and second defect photodetectors 12, 14 are electrically connected to a track control circuit (not shown). The optical head is configured to perform track control based on detection outputs from these photodetectors.

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

Here, in each of the above embodiments, the converging spots SP4 and SP5 for detecting a defect of the optical disk 7 are formed using the first and second folding mirrors 11 and 13, in the region where the light flux LB4, LB 5 passes, may be changing a propagation direction of the light beam. For example, the light beams LB4 and LB5 are condensed into spots SP4 and SP5.
So that a spot can be formed at the same position as
Even if another diffraction grating is provided in the area where the light beams LB4 and LB5 pass, there is no practical problem. Further, the present invention is effective in both cases of recording and reproducing information on an information recording medium.

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

[0020]

As described above, according to the present invention, the light source
Incident light flux outside the field of view of the focusing optics within the field of view
An optical system for guiding the light to the optical path is provided, and a focused spot for defect detection is arranged before a focused spot for obtaining at least a track error signal by the optical system, and the track control is fixed by the focused spot for defect inspection. Therefore, when a defect exists in the information recording medium, the focus spot for defect detection detects the defect and the track control is fixed before the focus spot for the track error signal scans the defect. As a result, the objective lens is fixed at that position, and track offset can be prevented. In addition, by arranging a focus spot for defect detection after a focus spot for obtaining a track error signal, it is possible to detect completion of scanning of a defect,
The fixed state of the track control can be released without complicating the track control circuit.

[Procedure amendment 12]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

Claims (6)

[Claims] An optical system for converging a light beam emitted from a light source onto a recording track of an information recording medium and receiving a reflected light beam from the information recording medium to obtain at least a track error signal; A track control system for controlling the focusing position of the emitted light beam based on the light flux for a defect on the recording track at a position before the emitted light beam is focused on the information recording medium. And a means for receiving a reflected light beam of the light beam for the defect and for setting the control of the track control system in a fixed state for a predetermined time according to a light receiving level of the reflected light beam for the defect. Light head. 2. The means for fixing the track control system includes: means for condensing a light beam for a second defect at a position at a time point after the emitted light beam is converged on the information recording medium; 2. The device according to claim 1, further comprising: means for releasing a fixed state of the control of the track control system according to a light receiving level of the reflected light flux for the second defect condensed at a position at a later point in time. 3. Light head. 3. The optical system, comprising: means for separating a light beam emitted from the light source into a plurality of light beams; and a reproduction / error light detection device for receiving the light beams reflected by the information recording medium. And a device for obtaining the track error signal at the output of the reproduction and error photodetector,
3. The optical head according to claim 1, wherein the means for setting the track control system in a fixed state uses one of the light beams separated by the means for separating the emitted light beam as the light beam for the defect. 4. . 4. A means for separating the emitted light beam into a plurality of light beams is a diffraction grating. The three light beams diffracted by the diffraction grating are condensed on a recording track of the information recording medium, and reflected light of each light beam is reflected. Are respectively received by a reproduction / error photodetector to obtain the track error signal, and the defect light beam uses a light beam other than the three light beams among the light beams diffracted by the diffraction grating. Item 4. The optical head according to item 3. 5. An optical system for focusing a light beam emitted from a light source on a recording track of an information recording medium and receiving a reflected light beam from the information recording medium to obtain at least a track error signal; A track control system for controlling the focusing position of the emitted light beam based on the light beam for a defect at a position before the emitted light beam is focused on the information recording medium, and A track control method for an optical head, comprising: receiving a reflected light beam of the defect light beam; and fixing the control of the track control system for a predetermined time in accordance with a light receiving level of the defect reflected light beam. 6. An optical system for converging a light beam emitted from a light source onto a recording track of an information recording medium and receiving a reflected light beam from the information recording medium to obtain at least a track error signal; A track control system for controlling the focusing position of the emitted light beam based on the first defect light beam at a position before the emitted light beam is focused on the information recording medium. And condensing the light beam for the second defect at a position at a later point in time, receiving the reflected light beam of the light beam for the first and second defects, and receiving the reflected light beam for the first defect. The control of the track control system is set to a fixed state according to a level, and the fixed state of the control of the track control system is released according to a light receiving level of the reflected light beam for the second defect. Truck control method.