JP2002083433A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the asymmetry of a tracking error signal or the off-track at the time of track control accompanied with the displacement of the optical axis of an optical disk device and the center axis of an optical distribution means. SOLUTION: The optical disk device capable of housing the optical disk is provided with a light source for emitting the light, an objective lens for converging the light emitted from the light source to the optical disk, a 1st optical distribution means for outputting a transmission light and 1st and 2nd diffracted light beams while moving integrally with the objective lens, a transmission light detecting means for detecting the transmission light to output a TE1 signal showing the displacement of the detected transmission light, a 1st diffracted light detecting means for detecting the 1st and 2nd diffracted light beams to output a TE2 signal showing the difference between the detected amounts of 1st diffracted light and 2nd diffracted light, and a controller for producing the tracking error signal of the optical disk on the basis of the TE1 signal and the TE2 signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical disk device, and more particularly, to an optical disk device for obtaining an accurate tracking error signal of an optical disk.

[0002]

2. Description of the Related Art An optical disk is known as an information recording medium for recording a large amount of data. The optical disc can record information on tracks, and can also reproduce information recorded on the optical disc. The optical disk device is a device that can accommodate an optical disk and records information on the optical disk and / or reproduces information from the optical disk. In order for an optical disk device to record information on an optical disk or to reproduce information from the optical disk, to accurately record or reproduce the information on an appropriate track, a laser beam accurately tracks a track of the optical disk. )Must.
The tracking error signal indicates whether the laser beam is tracking the track accurately.

Hereinafter, a conventional optical disk device and a tracking error signal will be described.

FIG. 10A shows a conventional optical disk apparatus 100.
Indicates 0. 10A, a laser beam emitted from a light source 1010 is transmitted through an optical system 1015 to the optical disc 1.
070. Light reflected by the optical disk 1070 is detected by the photodetector 1050. Based on a result detected by the photodetector 1050, the control device 1085 controls any one of the light source 1010, the optical system 1015, and the optical disk 1070. The optical system 1015 includes, for example, a polarizing beam splitter 1020 having a split surface 1025,
30, a quarter-wave plate 1042, a reflection mirror 1040, and an objective lens 1060.

Hereinafter, a more specific operation of the optical disk device 1000 will be described. The laser light emitted from the light source 1010 enters the polarization beam splitter 1020,
Split surface 102 of polarizing beam splitter 1020
5 and is converted into parallel light by a collimating lens 1030. The parallel light passes through the quarter-wave plate 1042 and is converted from linearly polarized light (P wave) to circularly polarized light.
The light is reflected by the reflection mirror 1040. The reflected light is converged on the signal surface 1074 of the optical disk 1070 by the objective lens 1060. The signal surface 1074 of the optical disc 1070 is formed between the base 1072 and the protective film 1076. The signal surface 1074 has a depth d, a pitch p, and a width w along the radial direction of the optical disk 1070 (that is, a direction perpendicular to the direction of light incident on the optical disk 1070 and parallel to the paper surface). Grooves or pits are formed. The light reflected by the signal surface 1074 passes through the objective lens 1060 and the reflection mirror 1040, and is converted into linearly polarized light (S wave) by the 波長 wavelength plate 1042. After that, the light becomes convergent light by the collimating lens 1030 and the split surface 1 of the polarizing beam splitter 1020 is split.
025 and reflected as light 1080 by photodetector 1
It is focused on 050. Based on the signal detected by the photodetector 1050, the control device 1085
0, any one of the optical system 1015 and the optical disk 1070 is controlled.

FIG. 10B shows a configuration of the photodetector 1050. Photodetector 1050 includes sub photodetectors 1050A and 1050B. A dividing line 1051 indicates a boundary between the sub photodetectors 1050A and 1050B. A tracking error signal 1091s (TE1 signal) can be obtained by subtracting the amount of light detected by each of the sub-light detectors 1050A and 1050B by the subtractor 1091, and the added signal is added by the adder 1092 to obtain the reproduction signal 109.
2s can be obtained. The division line 1051 is the photodetector 1
The convergent spot 1081 on 050 is almost equally divided. The controller 1085 controls the laser light source 10 so that the TE1 signal becomes zero in order to eliminate a tracking error.
10, an optical system 1015 and an optical disk 1070 are controlled.

FIG. 11A shows another conventional optical disk apparatus 1.
100 is shown. Laser light emitted from the light source 1110 is converged on the optical disk 1170 via the optical system 1115. Light reflected by the optical disk 1170 is detected by the photodetector 1190. Based on the result detected by the light detector 1190, the controller 1185
Is a light source 1110, an optical system 1115, an optical disk 117
Control any of the zeros. The optical system 1115 is
For example, the collimating lens 1130, the 波長 wavelength plate 11
42, polarization hologram element 1145, objective lens 116
Contains 0.

Hereinafter, a more specific operation of the optical disk device 1100 will be described. The light beam emitted from the light source 1110 is converted into parallel light by the collimator lens 1130 and is incident on the polarization hologram element 1145. The polarization hologram element 1145 has an objective lens 1160
Together with the lens holder 1165. The polarization hologram element 1145 also has a quarter-wave film 1142. The surface of the polarization hologram element 1145 is a polarization hologram surface 1150. The light (P wave) incident on the polarization hologram element 1145 passes through the polarization hologram surface 1150 and is converted from linearly polarized light (P wave) to circularly polarized light by the １ ／ wavelength film 1142.
0 and the signal surface 117 of the optical disc 1170
4 converges. The signal surface 1174 is
0 between the protective film 1172 and the base material 1176. On the signal surface 1174, grooves or pits having a depth d, a pitch p, and a width w are formed along the rotation direction of the optical disk 1170. The light reflected by the signal surface 1174 is converted into linearly polarized light (S-wave) by the quarter-wave film 1142 through the objective lens 1160, and the polarization hologram surface 11
Diffracted at 50. The diffracted light is incident on the photodetector 1190 via the collimating lens 1130. Based on the signal detected by photodetector 1190, control device 1185 controls any of light source 1110, optical system 1115, and optical disk 1170.

FIG. 11B shows a configuration of the hologram surface 1150. The hologram surface 1150 includes two regions 1150a and 1150b divided by a division line 1152. Light 1151 reflected by optical disk 1170
Are substantially equally divided by a dividing line 1152.

FIG. 11C shows the structure of the photodetector 1190. The light detector 1190 includes two sub-light detectors 1190.
A and 1190B. The sub-light detectors 1190A and 1190B are separated by a dividing line 1191. Region 1 of hologram surface 1150 shown in FIG. 11B
The light diffracted through 150a is transmitted to the sub-light detector 119.
The light is focused on 0A as a spot 1181a. Also,
Light diffracted through the area 1150b of the hologram surface 1150 is spotted on the sub-light detector 1190B.
It is collected as 1b. The amount of light detected by each of the sub-light detectors 1190A and 1190B is subtracted by a subtractor 1101 to obtain a tracking error signal 1
101s (TE2 signal) can be obtained. Further, the amount of light detected by each of the sub-light detectors 1190A and 1190B can be added by the adder 1102 to obtain a reproduced signal 1102s. The controller 1185 controls TE2 to eliminate tracking errors.
An arbitrary one of the laser light source 1110, the optical system 1115, and the optical disk 1170 is controlled so that the signal becomes zero.

[0011]

The tracking error signals (TE1 signal, TE2 signal) obtained by the conventional optical disk devices 1000 and 1100 have the following problems. First, a tracking error signal (TE1 signal) obtained by the optical disc device 1000 will be described.

In the optical disc apparatus 1000 that has been subjected to tracking control by the control device 1085, generally, the objective lens 1060 is displaced in the radial direction (in the direction of the arrow K in FIG. 10A) following the core runout of the optical disc 1070.

FIGS. 12A to 12D show the objective lens 10.
10 shows a light intensity distribution of a radial cross section of the optical disk 1070 when the central axis 1220 of the optical disk 60 is displaced rightward by a distance X with respect to the optical axis 1210 of the optical disk device 1000. FIG. 12E schematically shows the positional relationship between the optical axis 1210 of the optical disc apparatus 1000 and the central axis 1220 of the objective lens 1060.

FIG. 12A shows a light intensity distribution 1 before light emitted from a light source 1010 passes through an objective lens 1060.
231 is shown. The light intensity distribution 1231 shows a Gaussian distribution centered on the optical axis 1210. At this time, FIG.
As shown in (e), the central axis 12 of the objective lens 1060
20 has a displacement X with respect to the optical axis 1210 of the optical disk device 1000.

FIG. 12 (b) shows that the light is
Shows the light intensity distribution 1232 after passing through the light source. When the radius (opening diameter) of the objective lens 1060 is the length r, the light intensity distribution at a position farther than the distance r from the central axis 1220 of the objective lens 1060 becomes zero. That is, the objective lens 106
Light outside the 0 opening edges 1240, 1250 is cut off.

FIG. 12 (c) shows that the light is
FIG. 14 shows a light intensity distribution 1233 after being reflected by the light source and before being incident on the objective lens 1060. FIG. The central axis 1215 of the light reflected by the optical disc 1070 is displaced by X to the right with respect to the central axis 1220 of the objective lens 1060. That is, the central axis 1215 of the reflected light is equal to the displacement X of the optical axis 1210 of the optical disc apparatus 1000.
Shifted by a factor of two. The light intensity distribution 1233 is changed by the diffraction at the groove on the signal surface 1074 to the optical disk 1070.
Is spread in the radial direction.

FIG. 12D shows a light intensity distribution 1234 after passing through the objective lens 1060. As in the case of FIG. 12B, the opening edge 1240 of the objective lens 1060,
Light outside 1250 is cut off.

When the displacement X is zero, the tracking error signal (TE1) of the photodetector 1050 shown in FIG.
By controlling so that is zero, the tracking of the optical disk is accurately controlled. However, if the displacement X is not zero, a tracking offset occurs.

As described above, the tracking error signal (TE1) of the photodetector 1050 shown in FIG.
The difference in the amount of light detected by the sub-light detectors 1050A and 1050B is shown. Optical axis 1210 and objective lens 106
When there is a displacement X between the central axis 1120 and the center axis 1120, the amount of light detected by each of the sub-light detectors 1050A and 1050B is determined by the area of the figure ABCD and the area of the figure CDEF shown in FIG. It corresponds to the area.

Note that the TE2 signal detected by the photodetector 1190 of the optical disk device 1100 also has the same offset when a displacement exists between the optical axis of the optical disk device 1100 and the center axis of the objective lens 1160.

As described above, the tracking error signal (TE2) of the photodetector 1190 is output from the sub photodetector 119.
0A and 1190B show the difference in the amount of light detected. Optical axis of optical disk device 1100 and objective lens 116
When there is a displacement X between the center X and the center axis of 0, the amount of light detected by the sub-light detectors 1190A and 1190B depends on the area of the figure ABC'D 'and the figure C' shown in FIG. It corresponds to the area of D'EF. Photodetector 119
In the case of the tracking error signal (TE2) of 0, a large error occurs although not as much as the tracking error signal (TE1) of the photodetector 1050.

FIG. 13A shows that the displacement X between the optical axis 1210 of the optical disc apparatus 1000 and the central axis 1220 of the objective lens 1060 is 100
Assuming μm, when crossing a groove (when tracking off)
3 is a graph showing the asymmetry of the tracking error signal waveform of FIG. The asymmetry is given by the formula (HL) / (H +
L), where H is the amplitude above the ground level GND of the signal output of the signal waveform shown in FIG. 13B, and L is the amplitude below the ground level GND of the signal output of the signal waveform shown in FIG. 13B. Means

In FIG. 13A, the horizontal axis represents the optical disk 10
The groove width w of 70 and the vertical axis indicate the groove depth (= d × (refractive index of the optical disc substrate 1072)) (see FIG. 10A). Also,
FIG. 13A shows the NA (numerical aperture) of the objective lens 1060 =
This is a calculation result when 0.60, the wavelength λ of the light source 1010 is set to 0.66 μm, and the groove pitch p of the optical disk 1070 is set to 0.74 μm. At a point R where the groove width w = 0.30 μm and the groove depth = λ / 10, TE asymmetry = 0.52
It turns out that it is. This corresponds to the area difference between the graphic ABCD and the graphic CDEF in FIG. That is, in the optical disc apparatus 1000 using the photodetector 1050, the central axis 1220 of the objective lens 1060 is used.
Has a displacement in the radial direction (X direction) with respect to the optical axis of the optical disc apparatus 1000, resulting in a large TE signal asymmetry, which makes tracking pull-in unstable. Alternatively, a very large off-track also occurs during track control, resulting in deterioration of reproduction performance due to leakage of a signal of an adjacent track (increase of crosstalk), or overwriting or erasing a part of a signal mark of an adjacent track. Problems also occur.

FIG. 14 shows an optical disk device 1100
The TE signal waveform asymmetry at the time of crossing the groove when the photodetector 1190 is used is shown under the same conditions. Groove width w = 0.
At a point R of 30 μm and groove depth = λ / 10, TE asymmetry = 0.18. This corresponds to FIG.
This corresponds to the area difference between the figures ABC'D 'and C'D'EF in (d). Although the asymmetry is small as compared with the case where the above-mentioned photodetector 1050 is used, a large asymmetry of the tracking error signal still occurs, resulting in instability of tracking pull-in or a large control error (off-track) during tracking control. The same problem as that in the case where the photodetector 1050 is used occurs, such as the occurrence of a photodetector.

In view of the above problems, the present invention suppresses the asymmetry of the tracking error signal due to the displacement between the optical axis of the optical disc device and the central axis of the light distribution means or off-track during track control, thereby achieving good reproduction or reproduction. An object of the present invention is to provide an optical disk device capable of performing stable recording.

[0026]

An optical disk apparatus capable of storing an optical disk includes a light source for emitting light, an objective lens for condensing the light emitted from the light source on the optical disk, and an integrated lens with the objective lens. Moving first light distribution means, wherein the first light distribution means comprises a first region and a second region;
Out of the reflected light reflected by the optical disc, the light transmitted through the first area or the second area is output as transmitted light, and the reflected light reflected by the optical disc is the A first diffracted light output as light diffracted by the first area, and a light diffracted by the second area out of the reflected light reflected by the optical disc as a second diffracted light; A light distributing means, a transmitted light detecting means for detecting the transmitted light and outputting a TE1 signal indicating a displacement of the detected transmitted light, and detecting the first diffracted light and the second diffracted light And
A first diffracted light detecting unit that outputs a TE2 signal indicating a difference between the detected amount of the first diffracted light and the amount of the second diffracted light, and based on the TE1 signal and the TE2 signal, A control device for generating a tracking error signal for the optical disc.

[0027] The transmitted light is directed to the transmitted light detecting means, and the first diffracted light and the second diffracted light are converted to the first diffracted light.
And a second light distribution means for directing the light to the diffracted light detection means.

The transmitted light detecting means includes a first sub transmitted light detecting means and a second sub transmitted light detecting means.
Is defined as light of the transmitted light detected by the first sub-transmitted light detection means, and second transmitted light is defined by the second sub-transmitted light detection means of the transmitted light. The displacement of the transmitted light may be defined as a detected light, and the displacement of the transmitted light may be defined as a difference between the amount of the first transmitted light and the amount of the second transmitted light.

The first diffracted light detecting means includes first sub-diffraction light detecting means for detecting the first diffracted light, and second sub-diffraction light detecting means for detecting the second diffracted light. May be included.

[0030] The control device may determine the tracking error signal by TE2-k × TE1.

The transmitted light detecting means includes a third region and a fourth region.
Wherein the third area is provided with the first sub-transmitted light detecting means, and the fourth area is provided with the second sub-transmitted light detecting means, A boundary between the third area and the fourth area may be parallel to a rotation direction of the optical disc.

The first diffracted light detection means includes a fifth area and a sixth area, and the fifth area is provided with the first sub-diffraction light detection means. The area 6 is provided with the second sub-diffraction light detection means,
A boundary between the fifth area and the sixth area may be parallel to a rotation direction of the optical disc.

The controller may update the value of k in accordance with the product (NA × P) of the numerical aperture (NA) of the objective lens and the radial groove pitch (P) of the optical disk. .

The value of k is 0.5 × S2 / S1 or less, S1 indicates the amount of transmitted light detected by the transmitted light detecting means, and S2 is detected by the first diffracted light detecting means. May be indicated.

The control device may determine that the product (NA × P) of the numerical aperture (NA) of the objective lens and the groove pitch (P) in the radial direction of the optical disk is 0.9 times the wavelength of light incident on the optical disk. In the above case, the value of k may be set to 0.

[0036] When the objective lens is moved in the radial direction of the optical disc without the tracking control being performed by the control device, the output average level of TE2−k × TE1 becomes substantially zero level. May be set to the value of k.

The apparatus further comprises aberration means for giving an aberration to the transmitted light, wherein the transmitted light detection means includes a third area, a fourth area, a seventh area, and an eighth area, Third
Area is provided with first sub-transmitted light detection means, and in the fourth area, second sub-transmitted light detection means is provided,
The seventh area is provided with a third sub-transmitted light detecting means, and the eighth area is provided with a fourth sub-transmitted light detecting means, wherein the third area and the fourth area are provided. Is parallel to the rotation direction of the optical disk, the boundary between the third area and the eighth area is parallel to the radial direction of the optical disk, and the fourth area and the seventh area are parallel to the radial direction of the optical disk. The boundary between the region and the region is parallel to the radial direction of the optical disk, the boundary between the seventh region and the eighth region is parallel to the rotation direction of the optical disk, and the third region is the third region. 7, the fourth region is positioned diagonally to the eighth region, and the control device is configured to control the first among the aberration-transmitted lights. The amount of transmitted light detected by the sub-transmitted light detecting means and the third sub-transmitted light detecting means Sum of the amount of transmitted light detected by the second sub-transmitted light detector and the amount of transmitted light detected by the second sub-transmitted light detector of the aberration-imparted transmitted light. The focus error signal of the optical disc may be obtained based on the difference between the amount of transmitted light and the sum of the detected amounts of transmitted light.

[0038] The first light distribution means includes a ninth area and a tenth area, and the first light distribution means is provided with the first light distribution part of the light reflected by the optical disk. The light diffracted by the ninth region of the means to a third
And the light diffracted by the tenth region of the first light distribution means out of the reflected light reflected by the optical disk is output as a fourth diffracted light, and the first diffraction light is output. The light detection means includes a first sub-diffraction light detection means, a second sub-diffraction light detection means, a three sub-diffraction light detection means, a fourth sub-diffraction light detection means, and a fifth sub-diffraction light detection means. Means, and sixth sub-diffraction light detection means, wherein the first diffraction light is detected by the first sub-diffraction light detection means and the second sub-diffraction light detection means,
The second diffracted light is detected by the fifth sub-diffracted light detecting means and the sixth sub-diffracted light detecting means, and the third diffracted light is detected by the fourth sub-diffracted light detecting means and the fourth sub-diffracted light detecting means. And the fourth sub-diffraction light detection means,
Is detected by the second sub-diffraction light detection means and the third sub-diffraction light detection means, and the control device controls the first sub-diffraction light detection means and the third sub-diffraction light detection means. The sum of the amounts of diffracted light detected by the detection means and the fifth sub-diffracted light detection means, the second sub-diffraction light detection means, the fourth sub-diffraction light detection means, and the sixth sub-diffraction light detection means The focus error signal of the optical disk may be obtained based on a difference from a sum of the amounts of the diffracted light detected by the diffracted light detecting means.

[0039] The apparatus further comprises second diffracted light detecting means, wherein the first light distributing means is provided with the first light distributing means based on the first area of the first light distributing means of the light reflected by the optical disk. The light diffracted separately from the diffracted light
Out of the reflected light reflected by the optical disc, the light diffracted separately from the second diffracted light by the second region of the first light distribution means into a sixth diffracted light And the second diffracted light detection means includes a seventh sub-diffraction detection means and an eighth sub-detection means, and the control device is configured to output the second sub-diffraction light detected by the seventh sub-diffraction detection means. 5, the amount of the diffracted light,
The focus error signal of the optical disk may be obtained based on a difference from the amount of the sixth diffracted light detected by the sub-detecting means.

The first light distribution means includes a hologram having a sawtooth-shaped cross-section or a structure having three or more steps cross-section inscribed in the sawtooth-shape. The first of the reflected light reflected
Outputting light diffracted separately from the first diffracted light by the first region of the light distribution means as fifth diffracted light;
Among the light reflected by the optical disc, light diffracted separately from the second diffracted light by the second region of the first light distribution means is output as sixth diffracted light, and the first And the amount of the fifth diffracted light output from the first light distributing means is different from the first diffracted light, and the amount of the second diffracted light output from the first light distributing means is different. And the amount of the sixth diffracted light may be different.

The first diffracted light and the second diffracted light outputted by the first light distribution means are first-order diffracted lights, and the fifth diffraction light outputted by the first light distribution means is provided. The light and the sixth diffracted light may be -1st-order diffracted light.

The amount of the -1st-order diffracted light may be substantially zero.

The amount of light output by the first light distribution means may be larger in the order of the -1st-order diffracted light, the transmitted light, and the first-order diffracted light.

The amount of light output by the first light distribution means may be larger in the order of the -1st order diffracted light, the 1st order diffracted light, and the transmitted light.

The amount of light output by the first light distribution means may be larger in the order of the first-order diffracted light, the -1st-order diffracted light, and the transmitted light.

[0046] The apparatus further comprises second diffracted light detecting means, wherein the first light distribution means includes a ninth area and a tenth area, and the first light distribution means includes a first light beam out of the light reflected by the optical disk. The light diffracted by the ninth region of the light distribution means is output as third diffracted light, and the light reflected by the optical disk is diffracted by the tenth region of the first light distribution means. And outputs the separated light as fourth diffracted light, of the reflected light reflected by the optical disk, the light diffracted separately from the first diffracted light by the first region of the first light distribution means. As the fifth diffracted light, and the light diffracted separately from the second diffracted light by the second area of the first light distribution means out of the reflected light reflected by the optical disc into the sixth diffracted light Output as diffracted light The second diffraction light detection means, first
Area 1, the twelfth area, the thirteenth area, and the fourteenth area.
Area, a fifteenth area, and a sixteenth area,
A first sub-diffraction light detection means is provided in the first area, an eighth sub-diffraction light detection means is provided in the twelfth area,
A ninth sub-diffraction light detecting means is provided in the thirteenth area, a tenth sub-diffraction light detecting means is provided in the fourteenth area, and an eleventh sub-diffraction light detecting means is provided in the fifteenth area. And a twelfth sub-diffraction light detecting means is provided in the sixteenth area, and the third diffracted light is separated by the seventh sub-diffraction light detecting means and the eighth sub-diffraction light detecting means. The fourth diffracted light is detected by the eleventh sub-diffracted light detecting means and the twelfth sub-diffracted light detecting means, and the fifth diffracted light is detected by the tenth sub-diffracted light detecting means. And the eleventh sub-diffraction light detection means, the sixth diffraction light is detected by the eighth sub-diffraction light detection means and the ninth sub-diffraction light detection means, and the control device , The seventh sub-diffraction light detecting means and the ninth sub-diffraction light detecting means. The amount of diffracted light detected by the folded light detecting means and the eleventh sub-diffracted light detecting means, the eighth sub-diffracted light detecting means, the tenth sub-diffracted light detecting means and the twelfth sub-diffraction light The focus error signal of the optical disk may be obtained based on a difference between the amount of the diffracted light detected by the light detecting unit and the amount of the diffracted light.

[0047] The apparatus further comprises second diffracted light detection means, wherein the first light distribution means includes a ninth area and a tenth area, and the first light distribution means includes a first light distribution section and a first light distribution section. The light diffracted by the ninth region of the light distribution means is output as third diffracted light, and the light reflected by the optical disk is diffracted by the tenth region of the first light distribution means. And outputs the separated light as fourth diffracted light, of the reflected light reflected by the optical disk, the light diffracted separately from the first diffracted light by the first region of the first light distribution means. As the fifth diffracted light, and the light diffracted separately from the second diffracted light by the second area of the first light distribution means out of the reflected light reflected by the optical disc into the sixth diffracted light Output as diffracted light The second diffraction light detection means, first
Area 1, the twelfth area, the thirteenth area, and the fourteenth area.
Area, a fifteenth area, and a sixteenth area,
A first sub-diffraction light detection means is provided in the first area, an eighth sub-diffraction light detection means is provided in the twelfth area,
A ninth sub-diffraction light detecting means is provided in the thirteenth area, a tenth sub-diffraction light detecting means is provided in the fourteenth area, and an eleventh sub-diffraction light detecting means is provided in the fifteenth area. And a twelfth sub-diffraction light detecting means is provided in the sixteenth area, and the third diffracted light is separated by the seventh sub-diffraction light detecting means and the eighth sub-diffraction light detecting means. The fourth diffracted light is detected by the eighth sub-diffracted light detecting means and the ninth sub-diffracted light detecting means, and the fifth diffracted light is detected by the tenth sub-diffracted light detecting means. And the eleventh sub-diffracted light detecting means, the sixth diffracted light is detected by the eleventh sub-diffracted light detecting means and the twelfth sub-diffracted light detecting means, and the control device , The seventh sub-diffraction light detecting means and the ninth sub-diffraction light detecting means. The amount of diffracted light detected by the folded light detecting means and the eleventh sub-diffracted light detecting means, the eighth sub-diffracted light detecting means, the tenth sub-diffracted light detecting means and the twelfth sub-diffraction light The focus error signal of the optical disk may be obtained based on a difference between the amount of the diffracted light detected by the light detecting unit and the amount of the diffracted light.

With the above configuration, the characteristic difference between the signal TE1 and the signal TE2 with respect to the displacement of the objective lens is used. For example, by using the calculated value TE2−k × TE1 as the tracking error signal, the asymmetry of the TE signal at the time of crossing the groove due to the displacement of the objective lens can be suppressed, and the off-track at the time of track control can be eliminated. Further, by using a hologram having a sawtooth-shaped cross section or a structure having three or more steps cross-section inscribed in the sawtooth shape for the second light distribution means, the S / N in the reproduced signal can be kept high. .

[0049]

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. 1A to 1C, FIGS. 2, 3 and 13.
A, 13B and FIG.

FIG. 1A shows an optical disk device 100 according to Embodiment 1 of the present invention. The laser light emitted from the light source 110 is transmitted to the optical disk 170 via the optical system 115.
Converges. The light reflected by the optical disk 170 is detected by the photodetector 200. Photodetector 200
Control device 185 based on the results detected by
Controls an arbitrary one of the light source 110, the optical system 115, and the optical disk 170. The optical system 115 is, for example,
Polarizing beam splitter 1 having split surface 125
20, collimating lens 1030, quarter wave plate 14
2, including the reflection mirror 140, the polarization hologram element 145, and the objective lens 160.

Hereinafter, a more specific operation of the optical disk device 100 will be described. 1A, a laser beam emitted from a light source 110 enters a polarizing beam splitter 120, and a split surface 1 of the polarizing beam splitter 120 is split.
The light passes through 25 and is converted by the collimating lens 130 into parallel light. The light source 110 is, for example, a semiconductor laser. The parallel light is reflected by the reflection mirror 140 and enters the polarization hologram element 145.

The polarization hologram element 145 is integrated with the lens holder 165 together with the objective lens 160. The polarization hologram element 145 is a quarter-wave film 1
42. The polarization hologram element 145 has a polarization hologram surface 150. The light (P wave) incident on the polarization hologram element 145 passes through the polarization hologram surface 150,
The 偏光 wavelength film 142 converts the linearly polarized light (P wave) into circularly polarized light. Thereafter, the light is condensed by the objective lens 160 and converged on the signal surface 174 of the optical disk 170.
The signal surface 174 is provided between the base 172 of the optical disc 170 and the protective film 176. The signal surface 174 has a depth d, a pitch p, and a width w along the rotation direction of the optical disc 170.
Grooves or pits are formed. The reflected light reflected by the signal surface 174 is converted into linearly polarized light (S wave) by the quarter wavelength film 142 of the polarization hologram element 145 via the objective lens 160, and is diffracted or transmitted by the polarization hologram surface 150. Note that, in this specification, the zero-order diffraction means transmission. Thereafter, the light is reflected by the reflecting mirror 140, becomes convergent light by the collimating lens 130, is reflected by the split surface 125 of the polarizing beam splitter 120, and is converted into light 180 by the photodetector 20.
It is focused on zero. The controller 185 controls any one of the laser light source 110, the optical system 115, and the optical disk 170 based on the signal detected by the photodetector 200. The photodetector 200 detects, for example, a focus error signal or a tracking error signal of the optical disc 170.

In this specification, the hologram element is the first hologram element.
Function as light distribution means. The polarization beam splitter functions as a second light distribution unit.

FIG. 1B shows a configuration of the polarization hologram surface 150. The polarization hologram surface 150 is divided into two regions 150a and 150b having different hologram patterns with a division line 152 parallel to the rotation direction of the optical disk 170 as a boundary. Light flux 1 reflected by optical disc 170
51 is almost equally divided by the dividing line 152. The transmitted light (0th-order light) and the diffracted light (for example, ± 1st-order diffracted light) passing through the polarization hologram surface 150 are reflected by the reflection mirror 140 and then converged by the collimator lens 130. Then, the polarizing beam splitter 12
The light is reflected by the zero split surface 125 and collected as light 180 on the photodetector 200.

FIG. 1C shows the structure of the photodetector 200.
The light detector 200 includes a transmitted light detector 210 for detecting transmitted light, a first diffracted light detector 220 and a second diffracted light detector 230 for detecting diffracted light. The transmitted light detector 210 is provided in a central region of the light detector 200. The first diffracted light detector 220 and the second diffracted light detector 230 are respectively provided in outer peripheral regions so as to sandwich the transmitted light detector 210.

The transmitted light detector 210 has four regions 210
C1, 210C2, 210C3, 210C4. The transmitted light detector 210 has four sub-transmitted light detectors 210A.
1, 210A2, 210B1, and 210B2. The sub-transmitted light detector 210A1 is provided in the area 210C1. The sub-transmission light detector 210A is provided in the region 210C2.
2 are provided. The sub-transmission light detector 210B1 is provided in the area 210C3. The sub-transmission light detector 210B2 is provided in the area 210C4. Area 210C
1, 210C2, 210C3, 210C4 are separated by orthogonal dividing lines 211 and 212. Dividing line 21
The direction 1 is parallel to the rotation direction of the optical disk 170.

The first outer edge area includes an area 220C1 and an area 220C2. A first diffracted light detector 220 is provided in the first outer edge area. First diffracted light detector 220
Includes two sub-diffraction light detectors 220A and 220B. The sub-diffraction light detector 220A is provided in the area 220C1. The region 220C2 includes the sub-diffraction light detector 2
20B are provided.

The second outer edge area includes an area 230C1 and an area 230C2. A second diffracted light detector 230 is provided in the second outer edge area. Second diffracted light detector 230
Includes two sub-diffraction light detectors 230A and 230B. The sub-diffraction light detector 230A is provided in the region 230C1. The region 230C2 includes the sub-diffraction light detector 2
30B is provided.

The -1st-order diffracted light diffracted by the region 150a of the polarization hologram surface 150 forms a focal point on the far side of the photodetector 230A and a spot 183 on the photodetector 230A.
a, and the region 15 of the polarization hologram surface 150
0a is diffracted by the first order diffracted light
It is converged on the spot as a spot 182a.

The first-order diffracted light diffracted by the region 150b of the polarization hologram surface 150 is collected as a spot 182b on the photodetector 220B,
The -1st-order diffracted light diffracted by the 0 region 150b forms a focal point before the photodetector 230B and
The light is focused on the spot as a spot 183b. Further, light transmitted through the polarization hologram surface 150 (zero-order light, that is, transmitted light) is condensed as a spot 181 substantially at the intersection of the dividing lines 211 and 212 of the transmitted light detector 210. However, the focal position is located on the far side of the detection surface of the transmitted light detector 210.

The amount of light detected by each of the sub-diffraction light detectors 220A and 220B of the first diffraction light detector 220 is subtracted by a subtractor 243 to obtain a second tracking error signal 243s (TE2 signal). Can be Further, the amounts of light detected by the respective sub-diffraction light detectors 220A and 220B are added by an adder 244 to obtain a reproduced signal 244s. The TE2 signal corresponds to the TE2 signal detected by the light detector 1190 shown in FIG. 11C.

The arithmetic unit 241 is provided with the sub-transmitted light detector 210
From the results detected by A1, 210A2, 210B1, 210B2, 210A1 + 210A2-210B
Output 1-210B2. The output of the calculator 241 is a first tracking error signal 241s (TE1 signal). The arithmetic unit 242 includes the sub-transmitted light detector 210
From the results detected by A1, 210A2, 210B1, 210B2, 210A1 + 210B2-210A
2-210B1 is output. The output of the calculator 242 is a third tracking error signal 242s (TE3 signal). Generally, the TE3 signal is called a phase difference TE signal. The TE1 signal is applied to the photodetector 1050 shown in FIG.
Corresponding to the detected TE1 signal.

As described above, the substantially rectangular transmission light detector 210 is replaced with the substantially rectangular sub transmission light detector 210A.
1, 210A2, 210B1, and 210B2, two sub-transmitted light detectors (210A) adjacent to each other along a direction parallel to the rotation direction of the optical disc 170 are provided.
1, 210A2) and the amount of light detected by the other 2
The difference from the amount of light detected by the two sub-transmitted light detectors (210B1, 210B2) is the TE1 signal. Also, two sub-transmitted light detectors (21
0A1, 210B2) and the amount of light detected by the other two sub-transmitted light detectors (210A2, 210B1).
Is the TE3 signal.

Further, the sub-diffraction light detectors 230A, 23
The amount of light detected by 0B is subtracted by a subtractor 245, and a focus error signal 245s (FE signal)
Can be obtained.

The control device 185 controls the TE1 signal and the TE1 signal.
A tracking error signal for the optical disk 170 is generated based on the two signals.

In the first embodiment, three types of tracking error signals (TE1, TE2, TE3 signals) can be obtained, and these signals can be used properly according to the type of the disk. For example, if the pit depth is 1/4
In the case of an optical disk (for example, a DVD-ROM disk) having a wavelength of about the wavelength, the control device 185 may use the TE3 signal as a tracking error signal for a pit signal (emboss signal).

On the other hand, when the optical disk is a disk having a guide groove, such as a DVD-RAM or DVD-R disk, the control device 185 determines the calculated value T using an appropriate constant k.
The result of E2-k × TE1 may be used as a tracking error signal. In this case, the control device 185 may update the value of k according to the type of the optical disc.

For example, when the groove pitch p of the optical disk 170 is 0.74 μm, the objective lens 160 moves in the radial direction (FIG. 1).
A (in the direction of arrow K in FIG. 13A), the TE1 signal is converted to the T1 signal in FIG. 13A as described for the photodetector 1050 in FIG. 10B.
The E1 signal asymmetry and the TE2 signal exhibit the TE2 signal asymmetry of FIG. 14 as described for the photodetector 1190 of FIG. 11C. Therefore, the lens shift amount is X, the true tracking error signal (a tracking error signal not affected by the lens shift) is TE, the total light reception amount of the transmitted light detector 210 is S1, and the total light reception amount of the first diffracted light detector 220 is The following equation is satisfied when the quantity is S2.

TE1 / S1 = TE + x (Equation 1) TE2 / S2 = TE + m × x (Equation 2) where the coefficient m is groove width w = 0.30 μm, groove depth = λ /
At a point R of 10, m = 0.18 / 0.52 = 1 /
2.89, groove width w = 0.34 μm, groove depth = λ /
At a point R ′ of 12, m = 0.22 / 0.62 = 1 /
2.82, and at points other than R, almost m = 1 /
It falls within a value near 2.89 (see FIGS. 13A and 14).

The following equation is established from (Equation 1) and (Equation 2).

TE = (TE2−k × TE1) / S2 (1-m) (Equation 3) where the coefficient k is given by the following equation.

K = m × S2 / S1 (Equation 4) Therefore, when the groove pitch p of the optical disk is 0.74 μm, the calculated value TE2 using the coefficient value k satisfying (Equation 4)
By using the result of −k × TE1 as the tracking error signal, a tracking error signal free from the influence of the lens shift can be obtained, and the asymmetry of the tracking error signal due to the displacement of the objective lens 160 can be suppressed.

FIG. 2 shows that the groove pitch p of the optical disk is 1.
FIG. 14B is a graph showing a contour map of the asymmetry of the TE2 signal waveform at the time of traversing the groove in the optical disc device 100 according to the first embodiment in the case of 23 μm (all other conditions are the same as those in FIG. 13A). Groove width w = 0.615 μm, groove depth = λ /
At the point S of No. 12, TE asymmetry = 0.00. Even if the groove depth and the groove width are slightly shifted from the point S, TE
The asymmetry is almost zero. This is the groove pitch p =
In the case of 1.23 μm, the light intensity distributions 1233 and 1234 in FIGS. 12C and 12D are substantially uniform, and the areas of the figures ABC′D ′ and C′D′EF are almost equal. It is.

Therefore, the groove pitch p of the optical disk is 1.2
In the case of 3 μm, when the control device 185 sets k = 0, the calculated TE signal (TE2−k × TE1) becomes equal to TE2, and a TE signal that is not affected by the lens shift is obtained.
The asymmetry of the TE signal accompanying the displacement of the objective lens is suppressed.

Therefore, in the first embodiment, the DVD-RAM
In the optical disk 170 having a large groove pitch, such as the above, the control device 185 sets k = 0. DVD-R and DVD
In the optical disk 170 having a small groove pitch such as -RW, the control device 185 sets k = m × S2 / S1. The value of m is a certain constant value in the range of, for example, 1/2 to 1/5, and the optimum value is the groove pitch of the disc, the numerical aperture (NA) of the objective lens, and the rim intensity ratio of light incident on the objective lens. (The ratio of the light intensity at the periphery of the lens to the peak intensity) may be determined. The update of the constant k by the control device 185 is performed by updating the numerical value (NA × P) of the product (NA × P) of the numerical aperture (NA) of the objective lens and the groove pitch (P) (or pit pitch (P)) in the radial direction of the optical disk. 0.9 times).

By this switching, the asymmetry of the TE signal due to the displacement of the objective lens is suppressed for different disks, and off-track during track control can be eliminated. The updating of the constant k may be performed not only once as in the above embodiment, but also plural times according to the pitch of the optical disk. Further, the optimum value of the constant k can be determined by learning. At this time, the arithmetic signal TE2 when the objective lens 160 is moved in the radial direction X of the optical disk 170 without the control device 185 performing tracking control.
The constant k may be set so that the output average level of −k × TE1 (the average value of the maximum value and the minimum value of the operation signal) becomes substantially zero level (ground level).

FIG. 3 shows a diffraction light amount ratio of the polarization hologram element 145 according to Embodiment 1 of the present invention. The polarization hologram surface 150 of the polarization hologram element 145 has almost no diffractive effect on the outward light (P wave), but has a diffractive effect on the backward light (S wave), and immediately after passing through the polarization hologram surface 150. 3 is also shown in FIG. The phase distribution 19 has a stepped shape inscribed in the sawtooth waveform, and the first stage 19 a and the second stage 19 for one cycle.
b, the width ratio of the third stage 19c is 37%, 25%, respectively.
38%, and the phase difference between the first and second stages and the second and third stages is 75 degrees, respectively.

The phase distribution has a periodic staircase shape 1 as shown in the figure.
9, diffracted light is generated, and if the total transmitted and diffracted light amount is 100%, the light amount of the zero-order light (transmitted light) is 20.
%, The light quantity of the first-order diffracted light is 47.6%, and the light quantity of the -1st-order diffracted light is 12.4%. The rest are assigned to higher order terms. In the optical disc device 100, the first-order diffracted light 1 detected by the sub-diffraction light detectors 220A and 220B
A reproduced signal is detected using the signals 82a and 182b. Therefore, when the ratio of the first-order diffracted light is increased as shown in FIG. 3, a signal having a high S / N can be obtained. Generally S
/ N is proportional to detection index = detected light quantity / √ (the number of detectors that detect light), and in the case of the first embodiment, detection index = 47.
6 / √2 = 34. The phase difference TE signal (TE3 signal) with respect to the pit signal (emboss signal) generally requires high-frequency signal processing. However, since about 20% of the light intensity of the zero-order light is allocated, from the viewpoint of S / N. no problem.

The optical disk device 1 according to the present embodiment
In 00, unlike the conventional optical disc apparatus 1100, since the light source 110 and the detector 200 are separately arranged,
The transmitted light can be used to determine a tracking error signal.

The optical disk device 1 according to the present embodiment
In FIG. 00, the configuration in which the polarization beam splitter 120 is provided is shown. However, those skilled in the art can consider any configuration in which the polarization beam splitter 120 is not provided.

Further, in the optical disk device 100 according to the present embodiment, the light emitted from the light source 110 is diffracted after being reflected by the optical disk 170.
Light can be efficiently incident on the photodetector 200.

In the above description, the case where the ± 1st-order diffracted light is used as the diffracted light is described. However, the present invention is not limited to this, and higher-order (eg, ± 2nd-order, 3rd-order) diffracted light is used. Can also be used. Further, the light spot 18
The first focus position may be before the detection surface of the transmitted light detector 210. At this time, since the light distribution is inverted with respect to the optical axis, the polarity of the TE1 signal changes.
May be replaced with -TE1, and the same effect can be obtained as in the above description.

(Embodiment 2) FIG. 4A schematically shows an optical disk device 300 according to Embodiment 2 of the present invention. The optical disc device 300 according to the second embodiment of the present invention
Except that the parallel flat plate 370 is arranged before the photodetector 400 and the configuration of the photodetector 400 is different, the configuration is the same as that of the optical disc device 100 described in the first embodiment. Is omitted. Optical disk drive 3
At 00, the parallel plate 370 is inclined with respect to the optical axis of the convergent light 380, and this inclination causes the photodetector 40.
An aberration (astigmatism) is added such that a focal line appears in the direction of ± 45 degrees with respect to the division line 411 (see FIG. 4B) on the plane 0. The parallel plate 370 functions as an aberration unit.

FIG. 4B shows a photodetector 40 according to the present embodiment.
Indicates 0. The light detector 400 includes a transmitted light detector 410 and a diffracted light detector 420.

The transmitted light detector 410 is the sub-transmitted light detector 4
10A1, 410A2, 410B1, 410B2. The transmitted light detector 410 includes the areas 410C1, 410C.
2, 410C3 and 410C4. The sub-transmission light detector 410A1 is provided in the area 410C1. Area 41
A sub-transmission light detector 410A2 is provided at 0C2.
The sub-transmission light detector 410B1 is provided in the area 410C3. The sub-transmission light detector 410B is provided in the area 410C4.
2 are provided. Regions 410C1, 410C2, 410
C3, 410C4 are separated by dividing lines 411 and 412 which are orthogonal to each other. The direction of the dividing line 411 is parallel to the rotation direction of the optical disk 170.

The diffracted light detector 420 includes two sub-diffraction light detectors 420A and 420B. Diffracted light detector 420
Includes regions 420C1 and 420C2. Area 420C
1 is provided with a sub-diffraction light detector 420A. Area 4
20C2 is provided with a sub-diffraction light detector 420B.

The first-order diffracted light diffracted in the region 150a of the polarization hologram surface 150 becomes a spot 382a focused before the sub-diffraction light detector 420A and focused on the sub-diffraction light detector 420A. The first-order diffracted light diffracted in the area 150b is transmitted to the
Sub-diffraction light detector 420B focusing behind the 20B
It becomes the spot 382b condensed on the upper side. In the present embodiment, it does not matter whether the focal position is located in front of or behind the detection surface, and may be located in front or behind.

Further, the light (zero-order light) transmitted through the polarization hologram surface 150 is condensed as a spot 381 substantially at the intersection of the dividing lines 411 and 412. At this time, the detection surface of the transmitted light detector 410 has two focal lines (vertical focal line and horizontal focal line).
It is located almost in the middle of. Therefore, before the spot 381 reaches the detection surface of the transmitted light detector 410, the dividing line 412
If the light passes through a focal line inclined clockwise by 45 ° with respect to the light, the light distribution becomes symmetrical with respect to this focal line direction, and the light distribution is 9 clockwise as compared with the spot 181 of the first embodiment.
This is equivalent to a light distribution rotated by 0 °.

The amount of light detected by each of the sub-diffraction light detectors 420A and 420B is subtracted by a subtractor 443 to obtain a second tracking error signal 443s.
(TE2 signal) is obtained. Also, the photodetectors 420a,
The amount of light detected by each of the light sources 420b is added by the adder 444 to obtain a reproduced signal 444s. The TE2 signal corresponds to the signal detected by the light detector 1190 shown in FIG. 11C.

The arithmetic unit 441 is provided with a sub-transmission light detector 410
From the results detected by A1, 410A2, 410B1, 410B2, 410A1-410A2 + 410B
1-410B2 is output. The output of the calculator 441 is a first tracking error signal 441s (TE1 signal). The arithmetic unit 442 includes a sub-transmission light detector 410
From the results detected by A1, 410A2, 410B1, 410B2, 410A1 + 410B2-410A
2-410B1 is output. The output of the calculator 442 is the third tracking error signal 11B (TE3 signal). The TE1 signal is applied to the photodetector 1050 shown in FIG.
Corresponding to the signal detected by

As described in the first embodiment, the substantially rectangular transmitted light detector 410 is replaced by the substantially rectangular sub-transmitted light detectors 410A1, 410A2, 410B1, 4
10B2, the direction parallel to the rotation direction of the optical disk 170 (90 clockwise as described above).
The light amount detected by the two sub-transmitted light detectors (410A1 and 410B1) adjacent to each other along the rotation direction of the optical disc 170 is rotated by 90 ° because of the rotation of the light distribution. Two sub-transmission light detectors (4
10A2, 410B2) is the TE1 signal. The amount of light detected by the two sub-transmission light detectors (410A1 and 410B2) arranged diagonally and the amount of light detected by the other two sub-transmission light detectors (410A2 and 410B1) are different. The difference from the quantity is the TE3 signal.

Further, the focus error of the objective lens 160 is reflected as astigmatism of the convergent light 381 (difference in spread in the direction of ± 45 degrees), so that 410A1 + 410B2
The signal 442s obtained by the calculator 442 that outputs −410A2 to 410B1 is a focus error signal (FE
Signal).

In the second embodiment, three types of tracking error signals (TE1, TE2, TE3 signals) can be obtained, but these signals can be selectively used according to the type of the disk as in the first embodiment. . For example,
When the optical disk has a pit having a quarter wavelength depth such as a DVD-ROM disk, the control device 185 may use the TE3 signal as a tracking error signal for the pit signal (emboss signal).

On the other hand, if the optical disc has a guide groove such as a DVD-RAM or DVD-R disc,
85 is an operation value TE2-k × TE1 using an appropriate constant k
May be used as the tracking error signal. In this case, the control device 185 can switch the value of the constant k according to the optical disc.

Therefore, as in the first embodiment, the asymmetry of the tracking error signal caused by the displacement between the optical axis of the optical disk system and the center axis of the objective lens is suppressed, and no off-track occurs during track control. Further, in the present embodiment, since the -1st-order diffracted light is not used, the hologram cross-sectional shape of the polarization hologram element 145 is changed so that the assignment of the -1st-order diffracted light becomes zero, and the 0th-order light and the 1st-order diffracted light are changed. It is possible to increase the S / N of the reproduction signal and the phase difference TE signal (that is, the TE3 signal) as compared with the first embodiment.

As a modification of the second embodiment, the sub-transmission light detectors 410A1, 410A2, 410B1, 4
There is also a method of detecting the sum signal of 10B2 as a reproduction signal. At this time, if the diffraction light amount ratio is assigned to 70% for the 0th-order light and 10% for the 1st-order diffraction light, the detection index of the reproduced signal is about 35. As described above, the light amount is −1 order light,
Primary light and transmitted light can be increased in this order.

In the above description, a parallel flat plate is used as the aberration means, but the present invention is not limited to this. For example, a wedge-shaped prism may be used as the aberration unit.

(Embodiment 3) FIG. 5A shows a configuration of a polarization hologram surface 550 according to Embodiment 3 of the present invention. FIG. 5B shows a configuration of photodetector 500 according to Embodiment 3 of the present invention. The optical disk device according to the third embodiment of the present invention is the same as the optical disk device according to the first embodiment except that the configuration of the polarization hologram surface 550 and the configuration of the photodetector 500 are different. Refers to the reference numbers in FIG. 1A.

In FIG. 5A, the polarization hologram surface 550
Is a dividing line 552 parallel to the rotation direction of the optical disc 170.
And four regions (550a, 550b, and 550) having different hologram patterns with a dividing line 553 orthogonal thereto as a boundary.
c, 550d). The reflected light beam 551 reflected by the optical disk 170 is divided into split lines 552 and 553.
Divides into approximately four equal parts. The first region 550a is further divided into strip regions along the division line 553 (specifically, the regions 550F11, 550B11, and 550F1).
2, 550B12, 550F13). Second area 550
b is divided into strip regions along the division line 553 (specifically, the regions 550B21, 550F21, 550B2
2, 550F22, 550B23). Third area 550
c is divided into strip regions along the division line 553 (specifically, the regions 550F31, 550B31, 550F3
2, 550B32, 550F33). Fourth region 550
d is divided into strip regions along the division line 553 (specifically, the regions 550B41, 550F41, 550B4
2, 550F42, 550B43).

In the first to fourth regions 550a to 550d,
The area indicated by “F” (for example, 550F11, 550F
The -1st-order diffracted light passing through 22) is collected before the photodetector 500. On the other hand, the region indicated by “B” (for example, 550B
11, 550B22) is the first order diffracted light.
Light is collected at the depth of 00.

The light detector 500 includes a transmitted light detector 510,
And first and second diffracted light detectors 520, 530. The transmitted light detector 510 is provided in a central region of the light detector 500. First and second diffracted light detectors 520, 5
30 are provided in two outer edge regions sandwiching the transmitted light detector 510.

The transmitted light detector 510 has four sub-transmitted light detectors 510A1, 510A2, 510B1, and 510B2.
including. The transmitted light detector 510 includes the regions 510C1, 51
0C2, 510C3, and 510C4. Area 510C
1 is provided with a sub-transmission light detector 510A1. The sub-transmission light detector 510A2 is provided in the area 510C2. The sub-transmission light detector 510B1 is provided in the area 510C3. The sub-transmission light detector 51 is provided in the area 510C4.
0B2 is provided. Regions 510C1, 510C2, 5
10C3 and 510C4 are dividing lines 51 orthogonal to each other.
1 and 512. The direction of the dividing line 511 is parallel to the rotation direction of the optical disk 170.

The first diffracted light detector 520 is provided in the first outer edge area. The first diffracted light detector 520 includes two sub-diffraction light detectors 520A and 520B. First diffracted light detector 520 includes regions 520C1 and 520C2. The sub-diffraction light detector 520A is provided in the area 520C1. The sub-diffraction light detector 520 is provided in the region 520C2.
B is provided.

The second diffracted light detector 530 provided in the second outer edge area has six sub-diffraction light detectors 530A1,
530A2, 530A3, 530B1, 530B2, 5
30B3. Sub-diffraction light detectors 530A1, 530
B2 and 530A3 are conducting, and the sub-diffraction light detectors 530B1, 530A2 and 530B3 are also conducting. The second diffracted light detector 530 includes the regions 530C1 and 530C5.
30C2, 530C3, 530C4, 530C5, 53
0C6. The sub-diffraction light detector 5 is provided in the region 530C1.
30A1 is provided. The sub-diffraction light detector 530A2 is provided in the area 530C2. The sub-diffraction light detector 530A3 is provided in the area 530C3. Area 530C
4 is provided with a sub-diffraction light detector 530B1. The sub-diffraction light detector 530B2 is provided in the area 530C5. The sub-diffraction light detector 530B3 is provided in the area 530C6.

First region 55 of polarization hologram surface 550
Strip area 550B1 located at every other position on 0a
The first-order diffracted light diffracted through the first and 550B12 is condensed on the sub-diffraction light detector 520B as a spot 582B1, and the -1st-order diffracted light is detected as a spot 583B1 straddling the sub-diffraction light detector 530B2. Focus on 530B3.

First region 55 of polarization hologram surface 550
0a remaining strip areas 550F11, 550F12, 5
The first-order diffracted light diffracted through the 50F13 is collected as a spot 582F1 on the sub-diffraction light detector 520B,
The -1st-order diffracted light is formed as a spot 583F1 over the sub-diffraction light detector 530B3.
Focus on 2

Second region 55 of polarization hologram surface 550
0b, every other strip area 550B2
The first-order diffracted light diffracted through 1, 550B22, 550B23 is condensed on the sub-diffraction light detector 520A as a spot 582B2, and the -1st-order diffracted light is detected as the light detector 530A1
Is condensed on the sub-diffraction light detector 530A2 as a spot 583B2 straddling the.

Second region 55 of polarization hologram surface 550
The first-order diffracted light diffracted through the remaining strip regions 550F21 and 550F22 of Ob is condensed on the sub-diffraction light detector 520A as a spot 582F2, and the −1st-order diffracted light is spot 58 across the sub-diffraction light detector 530A2.
The light is focused on the sub-diffraction light detector 530A1 as 3F2.

Third region 55 of polarization hologram surface 550
0c, every other strip area 550B3
The first-order diffracted light diffracted through the first and fifth light beams 550B32 is condensed on the sub-diffraction light detector 520A as a spot 582B3, and the -1st-order diffracted light is detected as a spot 583B3 across the sub-diffraction light detector 530A3.
Focus on 0A2.

Third region 55 of polarization hologram surface 550
0c remaining strip areas 550F31, 550F32, 5
The first-order diffracted light diffracted through the 50F33 is collected as a spot 582F3 on the sub-diffraction light detector 520A,
The -1st-order diffracted light is formed as a spot 583F3 over the sub-diffraction light detector 530A2.
Focus on 3

The fourth region 55 of the polarization hologram surface 550
Strip area 550B4 positioned every other on 0d
The first-order diffracted light diffracted through 1, 550B42, 550B43 becomes a spot 582B4 converged on the sub-diffraction light detector 520B, and the -1st-order diffracted light becomes a spot 583B4 straddling the sub-diffraction light detector 530B2. The light is focused on the detector 530B1.

The fourth region 55 of the polarization hologram surface 550
The first-order diffracted light diffracted through the remaining strip regions 550F41 and 550F42 of the sub-diffraction light detector 520B
The light is condensed on the spot as a spot 582F4, and the −1st-order diffracted light is spot 58 that straddles the sub-diffraction light detector 530B1.
The light is condensed on the diffraction light detector 530B2 as 3F4.

Further, the light (0th-order light) transmitted through the polarization hologram surface 550 is substantially divided by the dividing lines 511 and 51 in the central region.
The light is converged as a spot 581 at the intersection of the two. However, the focal position of the light spot 581 is determined by the transmitted light detector 510.
On the far side of the detection surface.

The light amounts detected by the sub-diffraction light detectors 520A and 520B of the first diffraction light detector 520 are subtracted by a subtractor 543 to obtain a second tracking error signal 543s (TE2 signal). 544 to obtain a reproduced signal 544s. TE
The two signals correspond to the TE2 signal described for the photodetector 1190 shown in FIG. 11C.

Here, the TE2 signal is calculated based on the amount of the first-order diffracted light passing through the first region 550a and the fourth region 550d of the polarization hologram surface 550 and the amount of the second-order diffraction light on the polarization hologram surface 550.
And the amount of the first-order diffracted light passing through the third region 550c. Further, the reproduction signal corresponds to the sum of the first-order diffracted lights in the first to fourth regions 550a to 550d of the polarization hologram surface 550.

The arithmetic unit 541 is provided with a sub-transmitted light detector 510
510A1 + 510A2-510B from the light amounts detected by A1, 510A2, 510B1, and 510B2.
1-510B2 is output. The output of the calculator 541 is a first tracking error signal 541s (TE1 signal). The arithmetic unit 542 includes a sub-transmission light detector 510A1,
From the light amounts detected by 510A2, 510B1 and 510B2, 510A1 + 510B2-510A2-5
10B1 is output. The output of the calculator 542 is a third tracking error signal 542s (TE3 signal).
The TE1 signal corresponds to the TE1 signal described for the photodetector 1050 shown in FIG. 10B.

As described in the first embodiment, the substantially rectangular transmission light detector 510 is replaced by the substantially rectangular sub transmission light detector 510A1, 510A2, 510B1,5.
10B2, the amount of light detected by two sub-transmission light detectors (510A1, 510A2) adjacent to each other along a direction parallel to the rotation direction of the optical disc 170 and the other two sub-transmissions Photodetector (510B
1, 510B2) is equal to T
This is the E1 signal. Also, the amount of light detected by the two sub-transmission light detectors (510A1, 510B2) arranged diagonally and the other two sub-transmission light detectors (510
A2, the difference from the amount of light detected by 510B1) is the TE3 signal.

Further, the sub-diffraction light detectors 530A1,5
30A2, 530A3, 530B1, 530B2, 53
The amount of light detected by 0B3 is 530B1 + 530B3 + 53
0A2-530A1-530A3-530B2.
5 s (FE signal) can be obtained.

In the third embodiment, three types of tracking error signals (TE1, TE2, TE3 signals) can be obtained. However, these signals are selectively used according to the type of the disk as in the first embodiment. You may. For example, an optical disk is a quarter of a DVD-ROM disk or the like.
When a pit having a wavelength depth is provided, the control device 185 may use the TE3 signal as a tracking error signal for the pit signal (emboss signal). On the other hand, when the optical disk is a disk having a guide groove such as a DVD-RAM or a DVD-R disk, the control device 185 may use the calculated value TE2-k × TE1 using an appropriate constant k as the tracking error signal. Good. In this case, the control device 1
Reference numeral 85 may update the value of the constant k according to the optical disk.

Therefore, as in the first embodiment, the asymmetry of the tracking error signal due to the displacement between the optical axis of the optical disk device and the center of the objective lens is suppressed, and no off-track occurs during track control. In the present embodiment, the hologram surface is subdivided into strips. In this region subdivided into strips, light converging before the detector 500 and light converging behind the detector 500 are generated, and the resulting diffracted light is detected as an FE signal. Therefore, the influence of dust and dirt on the disk base material 172 is canceled, and the stability of the focus error control is high.

In the above description, the sub-diffraction light detector 530B1 is used as the sub-diffraction light detector 530B3, 530A2.
And the sub-diffraction light detector 530B2 is in conduction with the sub-diffraction light detectors A1 and 530A3, and the difference between them is represented by F
Although the example in which the signal is generated as the E signal has been described, the sub-diffraction light detectors 530B1 and 530B3 are different from the sub-diffraction light detector 530A.
1, 530A3 and the sub-diffraction light detector 53
0B2 conducts with 530A2 and their difference signal (530
B1 + 530B3 + 530A1 + 530A3-530B
The FE signal can also be generated according to 2-530A2). In this case, the light spots 583B1 and 583F1 on the second diffracted light detector 530 are changed to the light spots 583B4 and 583B4.
83F4 (or the light spots 583B3 and 583F3 on the second diffracted light detector 530 become light spots 583B2,
583F2). Naturally, the first-order diffracted light side is also replaced accordingly.

Note that, of course, the hologram surface 5
There may be a form in which 50 is not subdivided into strips. When stripping is not performed on the hologram surface 550 shown in FIG. 5A, the first region 550a and the third region 550c of the hologram surface 550 are entirely indicated by “B”, and the second region of the hologram surface 550 is indicated by “B”. Region 550b, fourth region 55
0d is the area indicated by “F” on the entire surface, and the light spots 583F1, 583B2,
583F3, 583B4 and first diffracted light detector 52
Light spot 582F1, 582B2, 582F on 0
3 and 582B4 are eliminated, and light spots 583B1, 583F2 and 583 on the second diffracted light detector 530, respectively.
3B3, 583F4 and light spots 582B1, 582F2, 582B3, 5 on the first diffracted light detector 520.
Only 82F4 remains.

(Embodiment 4) FIG. 6A shows a configuration of a polarization hologram surface 650 according to Embodiment 4 of the present invention.
FIG. 6B shows a photodetector 600 according to Embodiment 4 of the present invention.
Is shown. The optical disc device according to the fourth embodiment of the present invention is different from the optical disc device 10 according to the first embodiment except that the configuration of the polarization hologram surface 650 and the configuration of the photodetector 600 are different.
0, and reference numerals in FIG. 1A are referred to for the description of the other components.

In FIG. 6A, the polarization hologram surface 650
Is a dividing line 652 parallel to the rotation direction of the optical disc 170.
And four regions (650a, 650b, 650) having different hologram patterns bordering on a dividing line 653 orthogonal to this.
c, 650d), and the reflected light beam 651 reflected by the optical disc 170 is divided into approximately four equal parts by the dividing lines 652, 653. The first region 650a is further divided into strip regions along the division line 653 (specifically, the regions 650F11, 650B11, 650F12,
650B12, 650F13). The second region 650b is divided into strip regions along the division line 653 (specifically, the regions 650B21, 650F21, 650B22,
650F22, 650B23). The third region 650c is divided into strip regions along the division line 653 (specifically, the regions 650F31, 650B31, 650F32,
650B32, 650F33). The fourth region 650d is divided into strip regions along the division line 653 (specifically, the regions 650B41, 650F41, 650B42,
650F42, 650B43).

In the first to fourth regions 650a to 650d,
The area indicated by “F” (for example, 650F11, 650F
The -1st-order diffracted light passing through 22) is collected before the photodetector 600. On the other hand, the region indicated by “B” (for example, 650B
11, 650B22) is the -1st-order diffracted light.
Light is collected at the depth of 00.

The light detector 600 includes a transmitted light detector 610
And first and second diffracted light detectors 620 and 630. The transmitted light detector 610 is provided in a central region of the light detector 600. First and second diffracted light detectors 620, 6
30 are provided in two outer edge regions sandwiching the transmitted light detector 610.

The transmitted light detector 610 includes four sub-transmitted light detectors 610A1, 610A2, 610B1, and 610B.
2 inclusive. The transmitted light detector 610 includes the regions 610C1, 6
10C2, 610C3, and 610C4. Region 610
C1 is provided with a sub-transmission light detector 610A1. The sub-transmission light detector 610A2 is provided in the area 610C2. The sub-transmission light detector 610B1 is located in the area 610C3.
Is provided. The sub-transmission light detector 6 is located in the area 610C4.
10B2 is provided. Regions 610C1, 610C2,
610C3 and 610C4 are dividing lines 6 orthogonal to each other.
11 and 612. The direction of the dividing line 611 is parallel to the rotation direction of the optical disk 170.

The first diffracted light area 620 provided in the first outer edge area includes two sub-diffraction light detectors 620A and 620A.
0B. The first diffracted light region 620 is a region 620C
1, 620C2. The sub-diffraction light detector 620A is provided in the area 620C1. The sub-diffraction light detector 620B is provided in the area 620C2.

The second diffracted light area 630 provided in the second outer edge area has six sub-diffraction light detectors 630A1 and 630A.
30A2, 630A3, 630B1, 630B2, 63
0B3. Sub-diffraction light detectors 630A1, 630B
2, 630A3 are conducting, and the sub-diffraction light detectors 630B1, 630A2, 630B3 are also conducting. The second diffracted light region 630 includes the regions 630C1, 630
C2, 630C3, 630C4, 630C5, 630C
6 inclusive. The sub-diffraction light detector 630 is located in the region 630C1.
A1 is provided. The sub-diffraction light detector 630A2 is provided in the area 630C2. The sub-diffraction light detector 630A3 is provided in the area 630C3. The sub-diffraction light detector 630B1 is provided in the region 630C4. Area 63
0C5 is provided with a sub-diffraction light detector 630B2.
The sub-diffraction light detector 630B3 is provided in the area 630C6.

First region 65 of polarization hologram surface 650
Strip region 650B1 located at every other position on line 0a
The first-order diffracted light diffracted through 1,650B12 is condensed as a spot 682B1 on the sub-diffraction light detector 620B, and the -1st-order diffraction light is detected as a spot 683B1 straddling the sub-diffraction light detector 630A1.
Focus on 0A2.

First region 65 of polarization hologram surface 650
0a, the remaining strip areas 650F11, 650F12,
The first-order diffracted light diffracted through 650F13 is collected as a spot 682F1 on the sub-diffraction light detector 620B, and the -1st-order diffracted light is detected as a spot 683F1 straddling the sub-diffraction light detector 630A2.
Focus on 0A1.

The second region 65 of the polarization hologram surface 650
0b, every other strip region 650B2
The first order diffracted light diffracted through 1,650B22,650B23 is spotted 682 on the sub-diffraction light detector 620A.
The -1st-order diffracted light is condensed as B2, and the
The light is focused on the sub-diffraction light detector 630A3 as a spot 683B2 extending over 30A2.

The second region 65 of the polarization hologram surface 650
The first-order diffracted light diffracted through the remaining strip regions 650F21 and 650F22 on the sub-diffraction light detector 620A
The light is condensed on the spot as a spot 682F2, and the -1st-order diffracted light is spot 68 that straddles the sub-diffraction light detector 630A3.
The light is focused on the sub-diffraction light detector 630A2 as 3F2.

The third region 65 of the polarization hologram surface 650
0c, every other strip area 650B3
The first-order diffracted light diffracted through 1,650B32 is collected as the spot 682B3 on the sub-diffraction light detector 620A, and the -1st-order diffracted light is detected as the spot 683B3 straddling the diffraction light detector 630B3.
Focus on 2

The third region 65 of the polarization hologram surface 650
0c remaining strip areas 650F31, 650F32, 6
The first-order diffracted light diffracting 50F33 is a sub-diffraction light detector 6
The first order diffracted light is condensed on the sub-diffraction light detector 630B3 as a spot 683F3 straddling the sub-diffraction light detector 630B2.

The fourth region 65 of the polarization hologram surface 650
Strip area 650B4 located every other on 0d
The first order diffracted light diffracted through 1, 650B42, 650B43 is spot 68 on the sub-diffraction light detector 620B.
The first-order diffracted light is condensed on the sub-diffraction light detector 630B1 as a spot 683B4 straddling the sub-diffraction light detector 630B2.

The fourth region 65 of the polarization hologram surface 650
The first-order diffracted light diffracted through the remaining strip regions 650F41 and 650F42 of the sub-diffraction light detector 620B
The spot 682F4 converges on the top, and the -1st-order diffracted light is spot 6 that straddles the subdiffraction light detector 630B1
The light is condensed on the sub-diffraction light detector 630B2 as 83F4.

Further, the light (0th-order light) transmitted through the polarization hologram surface 650 is substantially divided by the dividing lines 611 and 61 in the central region.
The light is converged as a spot 681 at the intersection of the two. However, the focal position is on the far side of the detection surface of the transmitted light detector 610.

The second tracking error signal 643s (TE2 signal) is obtained by subtraction from the light quantity detected by the sub-diffraction light detectors 620A and 620B by a subtractor 643, and is added by an adder 644 to obtain a reproduced signal 644s. it can. The TE2 signal corresponds to the TE2 signal described for the photodetector 1190 shown in FIG. 11C.

Here, the TE2 signal is equal to one of the first region 650a and the fourth region 650d of the polarization hologram surface 650.
Order diffracted light and second region 65 of polarization hologram surface 650
0b and the first order diffracted light of the third region 650c. In addition, the reproduction signal is the first signal on the polarization hologram surface 650.
To the fourth-order regions 650a to 650d.

The sub-transmission light detectors 610A1, 610A
The amount of light detected by 2, 610B1, 610B2 is 610A
1 + 610A2-610B1-610B2, the first tracking error signal 641
s (TE1 signal) is obtained, and 610A1 + 610B2-
Calculator 642 having relational expression of 610A2-610B1
The third tracking error signal 642s (TE3
Signal). The TE1 signal corresponds to the TE1 signal described for the photodetector 1050 shown in FIG. 10B.

Further, the arithmetic unit 645 includes sub-diffraction light detectors 630A1, 630A2, and 63 of the second diffraction light detector.
0A3, 630B1, 630B2, and 630B3, the amount of light detected is 630B1 + 630B3 + 630.
A2-630A1-630A3-630B2 are output. The output of the calculator 645 is the focus error signal 64
5 s (FE signal).

In the fourth embodiment, three types of tracking error signals (TE1, TE2, TE3 signals) can be obtained. However, these signals are used properly according to the type of the disk as in the first embodiment. obtain. For example, when the optical disc has pits having a quarter wavelength depth such as a DVD-ROM disc, the control device 185 may use the TE3 signal as a tracking error signal for the pit signal (emboss signal). On the other hand, when the optical disk is a disk having a guide groove such as a DVD-RAM or a DVD-R disk, the control device 185 may use the calculated value TE2-k × TE1 using an appropriate constant k as the tracking error signal. . In this case, the control device 185 may update the value of the constant k according to the optical disc.

Therefore, as in the first embodiment, the asymmetry of the tracking error signal due to the displacement between the optical axis of the optical disk device and the center axis of the objective lens is suppressed, and no off-track occurs during track control. In the present embodiment,
The hologram surface 650 is subdivided into strips. In each of the regions subdivided into strips, light condensed before the photodetector 600 and light condensed behind the photodetector 600 are generated, and the FE signal is detected from the diffracted light. So
The influence of dust and dirt on the disk substrate 172 is canceled, and the stability of focus error control is high. further,
In the present embodiment, as compared with the third embodiment, the dividing line between the detectors of the second diffracted light detector 630 that detects the focus error signal (that is, the sub-diffraction light detector 630).
A1 and the sub-diffraction light detector 630A2, between the sub-diffraction light detector 630A2 and the sub-diffraction light detector 630A3, and between the sub-diffraction light detector 630B1 and the sub-diffraction light detector 6
30B2, and between the sub-diffraction light detector 630B2 and the sub-diffraction light detector 630B3) are along the light diffraction direction, so that even if there is a wavelength error or a wavelength shift, the second diffraction light detector Since the spot on 630 moves along the dividing line, a focus detection error hardly occurs.

In Embodiments 1 and 3,
Although an FE detection error due to a wavelength error or a wavelength shift is likely to occur, there is an advantage that there is a margin for rotation adjustment of the photodetector. Whether or not the direction of the dividing line of the detector at the time of detecting the FE signal is aligned with the direction of diffraction of light depends on the design concept. In Embodiments 1 to 3 and the following embodiments, a configuration in which the direction of the dividing line is orthogonal to the diffraction direction will be described. However, a configuration in which the direction of the dividing line is aligned with the direction of diffraction as in the fourth embodiment is naturally conceivable. .

(Embodiment 5) FIG. 7A shows a configuration of a polarization hologram surface 750 according to Embodiment 5 of the present invention.
FIG. 7B shows a photodetector 700 according to Embodiment 5 of the present invention.
Is shown. The optical disk device according to the fifth embodiment of the present invention is different from the optical disk device according to the third embodiment except that the configuration of the photodetector 700 is different.
The same reference numerals in FIG. 1A are used for the description of the components of the other parts.

In FIG. 7A, the polarization hologram surface 750
Is a dividing line 752 parallel to the rotation direction of the optical disc 170.
And four regions (750a, 750b, and 750) having different hologram patterns with a dividing line 753 orthogonal to the boundary.
c, 750d). The reflected light beam 751 reflected by the optical disk 170 is divided into split lines 752 and 753
Divides into approximately four equal parts. The first region 750a is further divided into strip regions along the division line 753 (specifically, the regions 750F11, 750B11, and 750F1).
2,750B12,750F13). Second area 750
b is divided into strip regions along the division line 753 (specifically, the regions 750B21, 750F21, and 750B2
2,750F22,750B23). Third region 750
c is divided into strip regions along the dividing line 753 (specifically, the regions 750F31, 750B31, 750F3
2,750B32,750F33). Fourth region 750
d is divided into strip regions along the dividing line 753 (specifically, the regions 750B41, 750F41, and 750B4
2,750F42,750B43).

In the first to fourth regions 750a to 750d,
The area indicated by “F” (for example, 750F11, 750F
The -1st-order diffracted light passing through 22) is collected before the photodetector 700. On the other hand, the region indicated by “B” (for example, 750B
11, 750B22) passes through the photodetector 7
Light is collected at the depth of 00.

The light detector 700 includes a transmitted light detector 710
And first and second diffracted light detectors 720, 730. The transmitted light detector 710 is provided in a central region of the light detector 700. First and second diffracted light detectors 720, 7
Reference numerals 30 are provided in two outer edge regions sandwiching the transmitted light detector 710.

Transmitted light detector 710 includes two sub-transmitted light detectors 710A and 710B. Transmitted light detector 7
10 includes regions 710C1 and 710C2. Area 71
A sub-transmission light detector 710A is provided at 0C1. The sub-transmission light detector 710B is provided in the area 710C2. The region 710C1 and the region 710C2 are separated by a dividing line 711. The direction of the dividing line 711 is parallel to the rotation direction of the optical disk 170.

The first outer edge region has a first diffracted light detector 7
20 are provided. The first diffracted light detector 720 includes:
Four sub-diffraction light detectors 720A1, 720A2, 72
0B1 and 720B2. First diffracted light detector 720
Are the areas 720C1, 720C2, 720C3, and 720C
4 inclusive. The sub-diffraction light detector 72 is provided in the area 720C1.
0A1 is provided. The sub-diffraction light detector 720A2 is provided in the area 720C2. In the area 720C3,
A sub-diffraction light detector 720B1 is provided. Region 720
C4 is provided with a sub-diffraction light detector 720B2.

The second outer edge region has a second diffracted light detector 7
30 are provided. The second diffracted light detector 730 is
Six sub-diffraction light detectors 730A1, similarly to the second diffraction light detector 630 of the detector 600 shown in the third embodiment,
730A2, 730A3, 730B1, 730B2, 7
30B3. Sub-diffraction light detectors 730A1, 730
B2 and 730A3 are conducting, and the sub-diffraction light detectors 730B1, 730A2 and 730B3 are also conducting. The second diffracted light detector 730 includes the regions 730C1, 7
30C2, 730C3, 730C4, 730C5, 73
0C6. The sub-diffraction light detector 7 is located in the region 730C1.
30A1 is provided. The sub-diffraction light detector 730A2 is provided in the area 730C2. The sub-diffraction light detector 730A3 is provided in the area 730C3. Area 730C
4 is provided with a sub-diffraction light detector 730B1. The sub-diffraction light detector 730B2 is provided in the area 730C5. The sub-diffraction light detector 730B3 is provided in the area 730C6.

First region 75 of polarization hologram surface 750
Strip region 750B1 located at every other position on line 0a
The first-order diffracted light diffracted through 1,750B12 is condensed on the sub-diffraction light detector 720B1 as a spot 782B1, and the -1st-order diffracted light is detected as a spot 783B1 over the sub-diffraction light detector 730B2.
The light is focused on 30B3.

First region 75 of polarization hologram surface 750
The remaining strip areas 750F11, 750F12, and 7 of 0a
The first-order diffracted light diffracted through the 50F13 becomes a spot 782F1 condensed on the sub-diffraction light detector 720B1, and the -1st-order diffraction light becomes a spot 783F1 straddling the sub-diffraction light detector 730B3.
Focus on 0B2.

The second area 75 of the polarization hologram surface 750
Strip region 750B2 located at every other position on 0b
The first order diffracted light diffracted through 1, 750B22, 750B23 is spot 7 on the sub-diffraction light detector 720A2.
The first-order diffracted light is collected as a light detector 730.
The light is condensed on the sub-diffraction light detector 730A2 as a spot 783B2 extending over A1.

The second area 75 of the polarization hologram surface 750
The first-order diffracted light diffracted through the remaining strip regions 750F21 and 750F22 of the sub-diffraction light detector 720A
2 is condensed as a spot 782F2, and the -1st-order diffracted light is a spot 7 that straddles the sub-diffraction light detector 730A2.
The light is condensed on the sub-diffraction light detector 730A1 as 83F2.

The third region 75 of the polarization hologram surface 750
Strip area 750B3 located every other on 0c
The first-order diffracted light diffracted through 1,750B32 is condensed on the sub-diffraction light detector 720A1 as a spot 782B3, and the -1st-order diffracted light is detected as a spot 783B3 straddling the sub-diffraction light detector 730A3. Focus on 730A2.

The first-order diffracted light diffracted through the remaining strip regions 750F31, 750F32, and 750F33 of the polarization hologram surface 750 is collected as a spot 782F3 on the sub-diffraction light detector 720A1, and the -1st-order diffracted light is detected as the sub-diffraction light detection. 783F3 over the vessel 730A2
And condensed on the sub-diffraction light detector 730A3.

The fourth region 75 of the polarization hologram surface 750
Strip area 750B4 positioned every other on 0d
The first order diffracted light diffracted through 1, 750B42, 750B43 is spot 7 on the sub-diffraction light detector 720B2.
The first-order diffracted light is condensed on the sub-diffraction light detector 730B1 as a spot 783B4 straddling the sub-diffraction light detector 730B2.

The fourth region 75 of the polarization hologram surface 750
The first-order diffracted light diffracted through the remaining strip regions 750F41 and 750F42 of the sub-diffraction light detector 720B
2, and the -1st-order diffracted light is focused on the sub-diffraction light detector 730B1 as the spot 782F4.
The light is condensed on the sub-diffraction light detector 730B2 as 83F4.

Further, the light (zero-order light) transmitted through the polarization hologram surface 750 becomes a spot 781 condensed almost on the dividing line 711 in the central area. The focal point is the transmitted light detector 7
10 are located on the far side of the detection surface. Photodetector 710
A, and a first tracking error signal 741 s (TE
1 signal), and are added by the adder 742 to obtain a reproduced signal 742s. TE1 signal is shown in FIG. 10B
Corresponds to the TE1 signal described in the detector 1050.

As described in the first embodiment, when the substantially rectangular transmitted light detector 710 is disposed separately from the substantially rectangular sub-transmitted light detectors 710A and 710B, the optical disk 170 Separated parallel to the direction of rotation
The difference in the amount of light detected by 10A and 710B is TE
One signal. Also, the sub transmitted light detectors 710A, 71
The sum of the amounts of light detected by 0B is the reproduced signal.

Photodetectors 720A1, 720A2, 720
The amount of light detected by B1 and 720B2 is 720A1 + 720
The second tracking error signal 743s is calculated by the computing unit 743 having the relational expression of A2-720B1-720B2.
(TE2 signal) is obtained, and 720A1 + 720B2-7
The third tracking error signal 744s (TE3 signal) can be obtained by the calculator 744 of the relational expression of 20A2-720B1. The TE2 signal corresponds to the TE2 signal described in the photodetector 1190 shown in FIG. 11C.

Further, the arithmetic unit 745 includes the sub-diffraction light detectors 730A1 and 730A of the second diffraction light detector 730.
2,730A3,730B1,730B2,730B3
730B1 + 730B from the amount of light detected by
3 + 730A2-730A1-730A3-730B2
Is output. The output of the calculator 745 is a focus error signal 745s (FE signal).

Also in the present embodiment, the phase distribution of the wavefront immediately after passing through the polarization hologram surface 750 is set so as to form a staircase shape inscribed in a sawtooth waveform as in the first embodiment. In this case, the phase difference between the first and second stages and the second and third stages is considerably reduced, so that the diffraction light amount ratio is 70% for the 0th-order light, 15% for the first-order diffraction light, and -1. 5% can be assigned to the second order diffracted light. As a result, ± 1
Since the next diffraction efficiency is small and the diffraction loss is small, the total diffraction light amount (= 70 + 15 + 5 = 90%) is obtained in the first embodiment.
It is larger than. Thus, the magnitude of the light amount is −1
The order of the next light, the first light, and the transmitted light can be set.

Also in the fifth embodiment, three types of tracking error signals (TE1, TE2, TE3 signals) can be obtained. As in the first embodiment, these signals may be properly used depending on the type of the disk. For example,
In the case of an optical disk having pits with a quarter wavelength depth such as a DVD-ROM disk, the control device 185 may use the TE3 signal as a tracking error signal for a pit signal (emboss signal). On the other hand, when the optical disk is a disk having a guide groove, such as a DVD-RAM or a DVD-R disk, the control device 185 determines an appropriate constant k
May be used as the tracking error signal. In this case, the control device 18
5 may update the value of the constant k according to the optical disk.

Therefore, as in the first embodiment, the asymmetry of the tracking error signal due to the displacement between the optical axis of the optical disk device and the center axis of the objective lens is suppressed, and no off-track occurs during track control. In addition, the present embodiment
The hologram surface 750 is subdivided into strips. In each of the regions subdivided into strips, light converging before the photodetector 700 and diffracted light condensing behind the photodetector 700 are generated, and the FE signal is detected from the diffracted light. Therefore, the influence of dust and dirt on the disk substrate 172 is canceled, and the stability of the focus error control is high. Further, in the fifth embodiment, the detected light amount of the zero-order light (transmitted light) is used for detecting the reproduction signal, and the detection index thereof is 70 / √.
2 = approximately 50, which is larger than that of the first embodiment.
/ N can be secured.

(Embodiment 6) FIG. 8A shows a configuration of a polarization hologram surface 850 according to Embodiment 6 of the present invention.
FIG. 8B shows a photodetector 800 according to Embodiment 6 of the present invention.
Is shown. The optical disk device according to the sixth embodiment of the present invention is the same as the optical disk device according to the third embodiment except that the configuration of the photodetector 800 is different, and the reference numerals in FIG. I do.

In FIG. 8A, the polarization hologram surface 850 is shown.
Is a dividing line 852 parallel to the rotation direction of the optical disc 170.
And four regions (850a, 850b, and 850) having different hologram patterns with a dividing line 853 orthogonal to the boundary.
c, 850d). The reflected light beam 851 reflected by the optical disc 170 is divided into split lines 852 and 853.
Divides into approximately four equal parts. The first region 850a is further divided into strip regions along the division line 853 (specifically, the regions 850F11, 850B11, and 850F1).
2,850B12, 850F13). Second area 850
b is divided into strip regions along the division line 853 (specifically, the regions 850B21, 850F21, and 850B2
2,850F22, 850B23). Third region 850
c is divided into strip regions along the division line 853 (specifically, the regions 850F31, 850B31, 850F3
2,850B32, 850F33). Fourth region 850
d is divided into strip regions along the division line 853 (specifically, the regions 850B41, 850F41, and 850B4
2,850F42, 850B43).

In the first to fourth regions 850a to 850d,
The area indicated by “F” (for example, 850F11, 850F
The -1st-order diffracted light passing through 22) is collected before the photodetector 800. On the other hand, the region indicated by “B” (for example, 850B
11, 850B22) passes through the first-order diffracted light.
Light is collected at the depth of 00.

The light detector 800 includes a transmitted light detector 810
And first and second diffracted light detectors 820, 830. The transmitted light detector 810 is provided in a central region of the light detector 800. First and second diffracted light detectors 820, 8
Reference numeral 30 is provided in two outer edge regions sandwiching the transmitted light detector 810.

The transmitted light detector 810 includes two sub transmitted light detectors 810A and 810B. Transmitted light detector 810
Includes regions 810C1 and 810C2. Area 810C
In 1, a sub-transmission light detector 810A is provided. Area 8
In 10C2, a sub-transmission light detector 810B is provided.
The area 810C1 and the area 810C2 are separated by a dividing line 811.
Separated into two. The direction of the dividing line 811 is
0 is parallel to the rotation direction.

The first diffracted light detector 820 provided in the first outer edge region includes sub-diffraction light detectors 820A and 820B.
including. The first diffracted light detector 820 has a region 820C1,
820C2. The sub-diffraction light detector 820A is provided in the area 820C1. The sub-diffraction light detector 820B is provided in the area 820C2.

The second diffracted light detector 830 provided in the second outer edge region has sub-diffraction light detectors 830A1, 830A2, 830A3, and 830B as in the third embodiment.
1, 830B2 and 830B3. The second diffracted light detector 830 includes the regions 830C1, 830C2, and 830C.
3, 830C4, 830C5, 830C6. The sub-diffraction light detector 830A1 is provided in the area 830C1. The sub-diffraction light detector 830A2 is provided in the area 830C2. The sub-diffraction light detector 83 is provided in the area 830C3.
0A3 is provided. The sub-diffraction light detector 830B1 is provided in the area 830C4. The sub-diffraction light detector 830B2 is provided in the area 830C5. Area830C6
Is provided with a sub-diffraction light detector 830B3.

First region 85 of polarization hologram surface 850
Strip region 850B1 located at every other position on line 0a
The first-order diffracted light diffracted through 1,850B12 converges on the sub-diffraction light detector 820B as a spot 882B1, and the -1st-order diffracted light as a spot 883B1 straddling the sub-diffraction light detector 830B2. 8
The light is focused on 30B3.

First Region 85 of Polarization Hologram Surface 850
The remaining strip areas 850F11, 850F12, 8 of 0a
The first-order diffracted light diffracted through the 50F13 is collected as a spot 882F1 on the sub-diffraction light detector 820B,
The -1st-order diffracted light is converted into a spot 883F1 extending over the sub-diffraction light detector 830B3.
Focus on 2

Second region 85 of polarization hologram surface 850
0b, a strip region 850B2 located at every other position
The first order diffracted light diffracted through 1,850B22 and 850B23 is spot 88 on the sub-diffraction light detector 820A.
The light is collected as 2B2, and the -1st-order diffracted light is detected by the
The light is condensed on the sub-diffraction light detector 830A2 as a spot 883B2 straddling 1.

The second area 85 of the polarization hologram plane 850
The first-order diffracted light diffracted through the remaining strip regions 850F21 and 850F22 of Ob becomes a spot 882F2 converged on the sub-diffraction light detector 820A, and the −1st-order diffracted light spreads over the sub-diffraction light detector 830A2.
The light is condensed on the sub-diffraction light detector 830A1 as 3F2.

Third Region 85 of Polarization Hologram Surface 850
Strip region 850B3 located at every other position on 0c
The first-order diffracted light diffracted through 1,850B32 is condensed as a spot 882B3 on the sub-diffraction light detector 820A, and the -1st-order diffracted light is detected as a spot 883B3 straddling the sub-diffraction light detector 830A3. 8
The light is focused on 30A2.

Third Region 85 of Polarization Hologram Surface 850
The remaining strip areas 850F31, 850F32, 8 of 0c
The first-order diffracted light diffracted through the 50F33 is collected as a spot 882F3 on the sub-diffraction light detector 820A,
The -1st-order diffracted light is detected as a spot 883F3 over the sub-diffraction light detector 830A2.
Focus on 3

The fourth region 85 of the polarization hologram surface 850
Strip area 850B4 located every other on 0d
The first order diffracted light diffracted through 1,850B42,850B43 is spot 88 on sub-diffraction light detector 820B.
2B4, and the -1st-order diffracted light is detected by the
The light is condensed on the sub-diffraction light detector 830B1 as a spot 883B4 extending over two.

The fourth region 85 of the polarization hologram surface 850
The first-order diffracted light diffracted through the remaining strip regions 850F41 and 850F42 of the sub-diffraction light detector 820B
The light is condensed on the spot as a spot 882F4, and the -1st-order diffracted light is spot 88 that straddles the sub-diffraction light detector 830B1.
The light is condensed on the sub-diffraction light detector 830B2 as 3F4.

Further, the light (zero-order light) transmitted through the polarization hologram surface 850 is condensed as a spot 881 on almost the dividing line 811 in the central area. Sub transmitted light detector 810A,
The first tracking error signal 841 s is subtracted by a subtractor 841 from the light amount detected by 810B.
(TE1 signal) is obtained and added by the adder 842 to obtain a reproduced signal 842s. The TE1 signal is the TE1 signal described in the photodetector 1050 shown in FIG. 10B.
Signal.

Based on the light amounts detected by the sub-diffraction light detectors 820A and 820B of the first diffraction light detector 820,
The subtractor 843 outputs the second tracking error signal 842s
(TE2 signal) can be obtained. The TE2 signal is shown in FIG.
1C corresponds to the TE2 signal described in the photodetector 1190.

Further, the sub-diffraction light detectors 830A1, 830A2, 830A3, 8 of the second diffraction light detector 830
Based on the amounts of light detected by 30B1, 830B2, and 830B3, arithmetic unit 845 calculates 830B1 + 830B3 + 83
0A2-830A1-830A3-830B2 are output. The output of the arithmetic unit 845 is the focus error signal 84
5 s (FE signal).

In the present embodiment, the polarization hologram surface 850 is used.
Unlike the first embodiment, the phase distribution of the wavefront immediately after transmitting the light is set to form a periodic rectangular shape (a so-called two-level grating shape). In this case, the phase difference between the lower stage and the upper stage is considerably small, and the amount of diffracted light is allocated to 70% for the 0th-order light, 10% for the 1st-order diffracted light, and 10% for the -1st-order diffracted light. Therefore, the diffraction loss is small due to the small diffraction efficiency, and the total diffraction light amount (= 70 + 10 + 10 = 90%) is larger than that in the first embodiment. In this way, the magnitude of the light amount can be set to the order of the first-order diffracted light, the -1st-order diffracted light, and the transmitted light. Further, the magnitude of the light amount is the first-order diffracted light, -1.
The order of next diffracted light and transmitted light may be used.

Also in the sixth embodiment, two types of tracking error signals (TE1 and TE2 signals) can be obtained. Therefore, similarly to Embodiment 1, control device 185 calculates operation value TE2-k × using an appropriate constant k.
Using TE1 as a tracking error signal, the value of the constant k can be updated according to the optical disk.

As in the first embodiment, the asymmetry of the tracking error signal due to the displacement between the optical axis of the optical disk device and the center axis of the objective lens is suppressed, and no off-track occurs during track control. In the present embodiment, the hologram surface 850 is subdivided into strips. In each of the regions subdivided into strips, light condensed before the surface of the detector 800 and diffracted light condensed behind the detector 800 are generated, and the FE signal is detected from the diffracted light. So
The influence of dust and dirt on the disk substrate 172 is canceled, and the stability of focus error control is high.

Further, in the sixth embodiment, the detected light quantity of the 0th-order light (transmitted light) is used when detecting the reproduced signal, and the detection index thereof is about 70 / √2 = 50. Larger S / N can be secured as compared with. However, in the present embodiment, the third tracking error signal (TE3 signal)
Cannot be obtained, the control device 185 controls the DVD-ROM
Tracking cannot be performed on a pit signal (emboss signal) of an optical disk such as a disk having pits having a depth of about 1/4 wavelength.

In the sixth embodiment, the detected light quantity of the zero-order light is used for detecting the reproduced signal, but the detected light quantity of the first-order diffracted light may be used. The amount of light detected by the sub-diffraction light detectors 820A and 820B is added by an adder 844 to obtain a reproduced signal 8
44s can be obtained. In this case, the phase distribution of the wavefront immediately after passing through the polarization hologram surface 850 is the same as that of the first embodiment, that is, 20% for the light amount of the 0th-order light, 47.6% for the light amount of the 1st-order diffracted light, and −1st time. 12.4% for the amount of folded light
And the detection index of the reproduced signal = 47.6 / √2 = 34.

(Embodiment 7) FIG. 9A shows a configuration of a polarization hologram surface 950 according to Embodiment 7 of the present invention.
FIG. 9B shows a photodetector 900 according to Embodiment 7 of the present invention.
Is shown. The optical disk device according to the seventh embodiment of the present invention is different from the optical disk device according to the third embodiment except that the configuration of the photodetector 900 is different.
1A is referred to for the description of the components of the other parts.

In FIG. 9A, the polarization hologram surface 950
Is a dividing line 952 parallel to the rotation direction of the optical disc 170.
And four regions (950a, 950b, and 950) having different hologram patterns with a dividing line 953 orthogonal to the boundary.
c, 950d). The reflected light beam 951 reflected by the optical disk 170 is divided into split lines 952 and 953.
Divides into approximately four equal parts. The first region 950a is further divided into strip regions along the division line 953 (specifically, the regions 950F11, 950B11, and 950F1).
2, 950B12, 950F13). Second area 950
b is divided into strip regions along the division line 953 (specifically, the regions 950B21, 950F21, 950B2
2,950F22, 950B23). Third area 950
c is divided into strip regions along the dividing line 953 (specifically, the regions 950F31, 950B31, 950F3
2, 950B32, 950F33). Fourth region 950
d is divided into strip regions along the division line 953 (specifically, the regions 950B41, 950F41, and 950B4
2, 950F42, 950B43).

In the first to fourth regions 950a to 950d,
The area indicated by “F” (for example, 950F11, 950F
The -1st-order diffracted light passing through 22) is collected before the photodetector 900. On the other hand, the region indicated by “B” (for example, 950B
11, 950B22) passes through the photodetector 9
Light is collected at the depth of 00.

The light detector 900 includes a transmitted light detector 910.
And first and second diffracted light detectors 920 and 930. The transmitted light detector 910 is provided in a central region of the light detector 900. First and second diffracted light detectors 920, 9
Reference numerals 30 are provided in two outer edge regions sandwiching the overlight detector 910.

The transmitted light detector 910 has four sub-transmitted light detectors 910A1, 910A2, 910B1, and 910B2.
including. The transmitted light detector 910 includes the regions 910C1, 91
0C2, 910C3, and 910C4. Area 910C
1 is provided with a sub-transmission light detector 910A1. The sub-transmission light detector 910A2 is provided in the area 910C2. The sub-transmission light detector 910B1 is provided in the area 910C3. The sub-transmission light detector 91 is provided in the area 910C4.
0B2 is provided. Areas 910C1, 910C2, 9
10C3 and 910C4 are dividing lines 91 orthogonal to each other.
1 and 912. The direction of the dividing line 911 is parallel to the rotation direction of the optical disc 170.

The first diffracted light detector 920 has a region 920C
Is provided.

The second diffracted light detector 930 provided in the second outer edge region has sub-diffraction light detectors 930A1, 930A2, 930A3, and 930B as in the third embodiment.
1, 930B2 and 930B3. The sub-diffraction light detectors 930A1 and 930A3 are conducting, and the sub-diffraction light detectors 930B1 and 930B3 are also conducting. The second diffracted light detector 930 includes the regions 930C1, 930C
2,930C3, 930C4, 930C5, 930C6
including. The sub-diffraction light detector 930A is provided in the region 930C1.
1 is provided. The sub-diffraction light detector 930A2 is provided in the area 930C2. The sub-diffraction light detector 930A3 is provided in the area 930C3. The sub-diffraction light detector 930B1 is provided in the area 930C4. Region 930
C5 is provided with a sub-diffraction light detector 930B2. The sub-diffraction light detector 930B3 is provided in the area 930C6.

First region 95 of polarization hologram surface 950
Strip region 950B1 located at every other position on 0a
The first order diffracted light diffracted through 1,950B12 is
Is collected as a spot 982B1 on the diffracted light detector 920, and the -1st-order diffracted light is formed as a spot 983B1 straddling the sub-diffracted light detector 930B2.
The light is focused on 30B3.

First region 95 of polarization hologram surface 950
The remaining strip areas 950F11, 950F12, 9 of 0a
The first-order diffracted light diffracted through the 50F13 is collected as a spot 982F1 on the first diffracted light detector 920,
The -1st-order diffracted light is formed as a spot 983F1 over the sub-diffraction light detector 930B3.
Focus on 2

Second region 95 of polarization hologram surface 950
0b, every other strip area 950B2
The first order diffracted light diffracted through 1, 950B22, 950B23 is spot 98 on the first diffracted light detector 920.
The first-order diffracted light is condensed on the sub-diffraction light detector 930A2 as a spot 983B2 straddling the sub-diffraction light detector 930A1.

The second region 950 of the optical hologram surface 950
The first-order diffracted light diffracted through the remaining strip regions 950F21 and 950F22 of b is collected as a spot 982F2 on the first diffracted light detector 920, and the -1st-order diffracted light straddles the sub-diffraction light detector 930A2. Spot 983
The light is focused on the sub-diffraction light detector 930A1 as F2.

Third region 95 of polarization hologram surface 950
0c, every other strip area 950B3
The first-order diffracted light diffracted through 1,950B32 converges on the first diffracted light detector 920 as a spot 982B3, and the -1st-order diffracted light is a sub-diffracted light as a spot 983B3 straddling the sub-diffraction light detector 930A3. Detector 9
The light is focused on 30A2.

Third region 95 of polarization hologram surface 950
0c remaining strip areas 950F31, 950F32, 9
The first-order diffracted light diffracted through 50F33 is spot 9
Focused on the first diffracted light detector 920 as 82F3,
The -1st-order diffracted light is formed as a spot 983F3 over the sub-diffraction light detector 930A2.
Focus on 3

Fourth region 95 of polarization hologram surface 950
Strip area 950B4 located every other on 0d
The first-order diffracted light diffracted through the first 950B42 and the 950B43 forms a spot 98 on the first diffracted light detector 920.
The first-order diffracted light is condensed on the sub-diffraction light detector 930B1 as a spot 983B4 straddling the sub-diffraction light detector 930B2.

The fourth region 95 of the polarization hologram surface 950
The first-order diffracted light diffracted through the remaining strip regions 950F41 and 950F42 of 0d is condensed on the first diffracted light detector 920 as a spot 982F4, and the -1st-order diffracted light straddles the sub-diffraction light detector 930B1. Spot 98
The light is focused on the sub-diffraction light detector 930B2 as 3F4.

Further, the light (0th-order light) transmitted through the polarization hologram surface 950 is substantially divided by the dividing lines 911 and 912 in the central region.
Are condensed as a spot 981 at the intersection point of.

The reproduction signal 11d can be obtained from the amount of light detected by the first diffracted light detector 920.

Sub-diffraction light detector 9 of transmitted light detector 910
Based on the light amounts detected by 10A1, 910A2, 910B1, and 910B2, the arithmetic unit 941 calculates 910A1 + 9
Output 10A2-910B1-910B2. The output of the computing unit 941 is the first tracking error signal 941
s (TE1 signal). Also, the second diffracted light detector 9
30 sub-diffraction light detectors 910A1, 910A2, 91
From the light amounts detected by 0B1 and 910B2, the arithmetic unit 942 calculates 910A1 + 910B2-910A2-91.
0B1 is output. The output of the calculator 942 is a third tracking error signal 942s (TE3 signal). T
The E1 signal corresponds to the TE1 signal described in the photodetector 1050 shown in FIG. 10B.

Further, the sub-diffraction light detectors 930A1, 930A2, 930A3, 9 of the second diffraction light detector 930
From the light amounts detected by 30B1, 930B2, and 930B3, a detection signal 1 for 930B1 + 930B3 is obtained.
Detection signals 11f, 930A1 for 1e, 930B2
A detection signal 11g for + 930A3 and a detection signal 11h for 930A2 are obtained. Detection signal 11g + 11
The second tracking error signal (TE2 signal) is obtained by calculating the relational expression of h-11e-11f, and 11e-1
A focus error signal (FE signal) can be obtained by calculating the relational expression of 1f-11g + 11h. The TE2 signal is the TE2 signal described in the photodetector 1190 shown in FIG. 11C.
This corresponds to two signals.

In this embodiment, the polarization hologram surface 95
The phase distribution of the wavefront immediately after passing through 0 is the same as that in the first embodiment, and the diffracted light amount is 20% for the 0th-order light, 47.6% for the 1st-order diffracted light, and 12.4 for the -1st-order diffracted light. % And so on.

In the seventh embodiment, three types of tracking error signals (TE1, TE2, TE3 signals) can be obtained. However, these signals are selectively used according to the type of the disk as in the first embodiment. obtain. For example, in the case of an optical disc having pits with a quarter wavelength depth such as a DVD-ROM disc, the control device 185 may use the TE3 signal as a tracking error signal for a pit signal (emboss signal). On the other hand, when the optical disk is a disk having a guide groove, such as a DVD-RAM or DVD-R disk, the control device 185 uses the calculated value TE2-k × TE1 using an appropriate constant k as a tracking error signal. Is also good. In this case, the control device 185 may update the value of the constant k according to the optical disc.

Therefore, as in Embodiment 1, the asymmetry of the tracking error signal due to the displacement between the optical axis of the optical disk device and the center axis of the objective lens is suppressed, and there is no off-track during track control. In the present embodiment, the hologram surface 950 is subdivided into strips. In each of the regions subdivided into strips, since the light condensed before the photodetector 900 and the light condensed behind the photodetector 900 are generated to detect the FE signal, Lumber 172
The influence of dust and dirt on the top is canceled, and the stability of focus error control is high. Further, in the seventh embodiment, one detector (that is, the first
Using a diffracted light detector 920), and its detection index =
About 47.6 S / N compared to Embodiment 1
Can be secured.

Although the first to seventh embodiments have been described above, the intent of the present invention is to simultaneously detect two types of tracking error signals (TE1 and TE2) conventionally used individually, The control unit 185 generates a more accurate tracking error signal from the two types of tracking error signals (TE1, TE2). Further, the control device 185 may use the calculated value TE2−k × TE1 using an appropriate constant k as the tracking error signal. Further, the hologram dividing method and the shape of the detector may be other forms, and the distribution of diffraction efficiency may be different. Further, the polarization hologram may be a non-polarization hologram or another light distribution element.

[0214]

According to the present invention described above, the calculated value TE2-k
By using × TE1 as the tracking error signal, the asymmetry of the tracking error signal at the time of traversing the groove due to the displacement of the objective lens can be suppressed, and off-track during track control can be eliminated. Can be done. Further, by employing a hologram having a sawtooth-shaped cross section or a structure of three or more steps inscribed in the sawtooth shape for the light distribution means such as a polarization hologram element, the S / N in the reproduced signal is also increased. It is possible to maintain and obtain a high signal reproduction capability.

[Brief description of the drawings]

FIG. 1A is a schematic diagram showing an optical disc device according to Embodiment 1 of the present invention.

FIG. 1B is a diagram showing a configuration of a hologram surface according to the first embodiment of the present invention.

FIG. 1C is a diagram showing a configuration of a photodetector according to Embodiment 1 of the present invention.

FIG. 2 is a contour diagram of a TE2 signal waveform asymmetry (groove pitch p) when crossing a groove in the optical disc device in the first embodiment.
= 1.23 μm).

FIG. 3 is a diffraction light amount ratio diagram of the polarization hologram element according to the first embodiment of the present invention.

FIG. 4A is a schematic diagram showing an optical disk device according to Embodiment 2 of the present invention.

FIG. 4B is a diagram showing a configuration of a photodetector according to Embodiment 2 of the present invention.

FIG. 5A is a diagram showing a configuration of a polarization hologram surface according to a third embodiment of the present invention.

FIG. 5B is a diagram showing a configuration of a photodetector according to Embodiment 3 of the present invention.

FIG. 6A is a diagram showing a configuration of a polarization hologram surface according to a fourth embodiment of the present invention.

FIG. 6B is a diagram showing a configuration of a photodetector according to Embodiment 4 of the present invention.

FIG. 7A is a diagram showing a configuration of a polarization hologram surface according to a fifth embodiment of the present invention.

FIG. 7B is a diagram showing a configuration of a photodetector according to Embodiment 5 of the present invention.

FIG. 8A is a diagram showing a configuration of a polarization hologram surface according to a sixth embodiment of the present invention.

FIG. 8B is a diagram showing a configuration of a photodetector according to Embodiment 6 of the present invention.

FIG. 9A is a diagram showing a configuration of a polarization hologram surface according to a seventh embodiment of the present invention.

FIG. 9B is a diagram showing a configuration of a photodetector according to Embodiment 7 of the present invention.

FIG. 10A is a schematic diagram showing an optical disc device in a first conventional example.

FIG. 10B is a diagram showing a configuration of a photodetector in a first conventional example.

FIG. 11A is a schematic diagram showing an optical disk device in a second conventional example.

FIG. 11B is a diagram showing a configuration of a polarization hologram surface in a second conventional example.

FIG. 11C is a diagram showing a configuration of a photodetector in a second conventional example.

12A to 12D are light intensity distribution diagrams in a radial cross section of an optical disc when there is a displacement between the optical axis of the optical disc system and the center of the objective lens, and FIG. FIG. 3 is a diagram schematically illustrating a positional relationship between an optical axis and a central axis of an objective lens.

FIG. 13A shows the T of the optical disk device in the first conventional example.
Contour map of E1 signal waveform asymmetry (groove pitch p = 0.7
4 μm).

FIG. 13B is a signal waveform for explaining signal asymmetry.

FIG. 14 shows a TE of the optical disk device in the second conventional example.
Contour diagram of two-signal waveform asymmetry (groove pitch p = 0.74)
μm).

[Explanation of symbols]

Reference Signs List 110 light source 120 polarization beam splitter 125 split surface 130 collimator lens 145 polarization hologram element 150 polarization hologram surface 142 quarter-wave plate 140 reflection mirror 160 objective lens 172 optical disk base material 174 optical disk base material 180 convergent light 181, 182a, 182b, 183a , 183b Light spot 200 Photodetector 210 Transmitted light detector 220, 230 Diffracted light detector 210A1, 210A2, 210B1, 210B2 Sub transmitted light detector 220A, 220B, 230A, 230B Sub diffracted light detector 241, 242, 243 245 Subtractor 244 Adder

 ──────────────────────────────────────────────────の Continuing on the front page (72) Kazuo Momio 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 5D118 AA18 BA01 CA24 CD02 CD03 CD11 CF03 CF05 CF17 DA06 DA08 DA20 DA33 DA35 DA43 DB09 DB13 5D119 AA29 BA01 EA02 EA03 EC07 JA12 JA14 JA15 JA23 JA25 KA17 KA19 LB05

Claims (22)

[Claims] 1. An optical disk device capable of housing an optical disk, comprising: a light source for emitting light; an objective lens for condensing the light emitted from the light source on the optical disk; A first light distribution unit, wherein the first light distribution unit includes a first area and a second area, and the first area or the second area of the reflected light reflected by the optical disc. The light transmitted through the area is output as transmitted light, the light diffracted by the first area among the reflected light reflected by the optical disk is output as the first diffracted light, and the reflected light reflected by the optical disk is output. A first light distribution unit that outputs light diffracted by the second region as light as second diffracted light, a TE1 signal that detects the transmitted light and indicates a displacement of the detected transmitted light. Transmitted light detecting means for outputting the first and second diffracted lights, and detecting a difference between the detected amount of the first diffracted light and the amount of the second diffracted light. An optical disc apparatus comprising: first diffracted light detection means for outputting a TE2 signal shown; and a control device for generating a tracking error signal for the optical disc based on the TE1 signal and the TE2 signal. 2. A second light distribution means for directing the transmitted light to the transmitted light detection means and for directing the first diffracted light and the second diffracted light to the first diffracted light detection means. The optical disk device according to claim 1, further comprising: 3. The transmitted light detecting means includes a first sub transmitted light detecting means and a second sub transmitted light detecting means, wherein the first transmitted light is the first of the transmitted lights. Defined as light detected by the sub-transmitted light detection means,
Is defined as light of the transmitted light detected by the second sub-transmitted light detecting means, and the displacement of the transmitted light is determined by the amount of the first transmitted light and the second transmitted light.
2. The optical disc device according to claim 1, wherein the optical disc device is defined as a difference from the amount of transmitted light. 4. The apparatus according to claim 1, wherein the first diffracted light detecting means includes
2. The optical disk device according to claim 1, further comprising: first sub-diffraction light detecting means for detecting the second diffracted light; and second sub-diffraction light detecting means for detecting the second diffracted light. 5. The control device according to claim 1, wherein the control device obtains the tracking error signal by TE2-k × TE1.
An optical disk device as described in the above. 6. The transmitted light detecting means includes a third area and a fourth area, wherein the third area is provided with the first sub transmitted light detecting means, 4. The area according to claim 3, wherein the second sub-transmitted light detecting means is provided, and a boundary between the third area and the fourth area is parallel to a rotation direction of the optical disc. An optical disk device as described in the above. 7. The first diffracted light detecting means includes a fifth area and a sixth area, and the fifth area includes the first area.
The second sub-diffraction light detecting means is provided in the sixth area, and the boundary between the fifth area and the sixth area is 5. The optical disk device according to claim 4, wherein said optical disk device is parallel to a rotation direction of said optical disk. 8. The control device according to claim 1, wherein a numerical aperture (NA) of the objective lens and a radial groove pitch (P) of the optical disc are provided.
The optical disk device according to claim 5, wherein the value of k is updated in accordance with a product of (NA x P). 9. The value of k is 0.5 × S2 / S1 or less, S1 indicates the amount of transmitted light detected by the transmitted light detecting means, and S2 indicates the amount of transmitted light detected by the first diffracted light detecting means. 6. The optical disk device according to claim 5, wherein the optical disk device indicates an amount of the diffracted light to be detected. 10. The control device according to claim 1, wherein a product (NA × P) of a numerical aperture (NA) of the objective lens and a groove pitch (P) in a radial direction of the optical disk is a value of 0.1.times. Of a wavelength of light incident on the optical disk. 9. The optical disk device according to claim 8, wherein the value of k is set to 0 when the value is 9 times or more. 11. The control device, when the control device moves the objective lens in a radial direction of the optical disc without performing tracking control, the control device performs a TE2-k × TE
6. The optical disk device according to claim 5, wherein the value of k is set such that an output average level of the output signal is substantially zero. 12. An optical system further comprising an aberration unit for giving an aberration to the transmitted light, wherein the transmitted light detection unit includes a third region, a fourth region,
A third sub-transmitted light detecting means is provided in the third area, and a second sub-transmitted light detecting means is provided in the fourth area. The seventh
Area is provided with a third sub-transmitted light detecting means, and in the eighth area, a fourth sub-transmitted light detecting means is provided,
The boundary between the third area and the fourth area is parallel to the rotation direction of the optical disk, and the boundary between the third area and the eighth area is parallel to the radial direction of the optical disk. The boundary between the fourth area and the seventh area is parallel to the radial direction of the optical disk, and the boundary between the seventh area and the eighth area is in the rotational direction of the optical disk. Parallel, the third region is located diagonally to the seventh region, the fourth region is located diagonally to the eighth region, and the control device is The sum of the amount of transmitted light detected by the first sub-transmitted light detecting means and the amount of transmitted light detected by the third sub-transmitted light detecting means in the transmitted light having an aberration; By the second sub-transmitted light detecting means of the transmitted light having the aberration, 2. The optical disk according to claim 1, wherein a focus error signal of the optical disk is obtained based on a difference between a detected amount of transmitted light and a sum of the amount of transmitted light detected by the fourth sub-transmitted light detection unit. apparatus. 13. The first light distribution means includes a ninth area and a tenth area, and the first light distribution means is configured to output the first light distribution light out of the light reflected by the optical disk. The light diffracted by the ninth region of the light distribution means is output as third diffracted light, and of the light reflected by the optical disk, the light is diffracted by the tenth region of the first light distribution means. The first diffracted light detecting means, the first sub-diffracted light detecting means, the second sub-diffracted light detecting means, the three sub-diffracted light detecting means, A fourth sub-diffraction light detecting means, a fifth sub-diffraction light detecting means, and a sixth sub-diffraction light detecting means, wherein the first diffracted light has a The second diffracted light detected by the second sub-diffraction light detecting means; Is detected by the fifth sub-diffraction light detection means and the sixth sub-diffraction light detection means, and the third
Is detected by the fourth sub-diffracted light detecting means and the fifth sub-diffracted light detecting means, and the fourth diffracted light is detected by the second sub-diffracted light detecting means and the third sub-diffracted light detecting means. The controller detects the diffracted light detected by the first sub-diffraction light detection means, the third sub-diffraction light detection means, and the fifth sub-diffraction light detection means. And the second
A focus error signal of the optical disk based on a difference between the sum of the amounts of diffracted light detected by the sub-diffraction light detecting means, the fourth sub-diffraction light detecting means, and the sixth sub-diffraction light detecting means. The optical disk device according to claim 1, wherein the value is determined. 14. The image forming apparatus according to claim 1, further comprising a second diffracted light detecting unit, wherein the first light distribution unit is configured to control the first light distribution unit based on the first area of the first light distribution unit out of the light reflected by the optical disk. The light diffracted separately from the first diffracted light is output as a fifth diffracted light, and the second light of the first light distribution means is included in the reflected light reflected by the optical disk.
And outputting the light diffracted separately from the second diffracted light by the area as the sixth diffracted light, wherein the second diffracted light detecting means comprises a seventh sub-diffraction detecting means and an eighth sub-detecting means The control device, the amount of the fifth diffracted light detected by the seventh sub-diffraction detecting means, the amount of the sixth diffracted light detected by the eighth sub-detecting means, The optical disk device according to claim 1, wherein a focus error signal of the optical disk is obtained based on a difference between the optical disk and the optical disk. 15. The first light distribution means includes a hologram having a sawtooth-shaped cross section or a structure having three or more steps cross-section inscribed in the sawtooth shape. Among the reflected light reflected by the optical disc, light diffracted separately from the first diffracted light by the first region of the first light distribution means is output as fifth diffracted light, and reflected by the optical disc. Of the first reflected light,
The light diffracted separately from the second diffracted light by the region is output as a sixth diffracted light, and the amount of the first diffracted light output from the first light distribution means and the fifth diffracted light are output. The optical disk device according to claim 1, wherein the amount of the diffracted light is different, and the amount of the second diffracted light and the amount of the sixth diffracted light output from the first light distribution means are different. . 16. The first diffracted light and the second diffracted light output by the first light distribution means are first-order diffracted lights, and the fifth diffracted light is output by the first light distribution means. 16. The optical disk device according to claim 15, wherein the diffracted light of (d) and the sixth diffracted light are -1st-order diffracted light. 17. The optical disk device according to claim 16, wherein the light amount of the -1st-order diffracted light is substantially zero. 18. The optical disk device according to claim 16, wherein the amount of light output by the first light distribution means is larger in the order of the -1st-order diffracted light, the transmitted light, and the first-order diffracted light. 19. The optical disk device according to claim 16, wherein the light amount output by said first light distribution means is larger in the order of said -1st-order diffracted light, said first-order diffracted light, and said transmitted light. 20. The optical disk device according to claim 16, wherein the amount of light output by the first light distribution means is larger in the order of the first-order diffracted light, the -1st-order diffracted light, and the transmitted light. 21. The apparatus according to claim 21, further comprising a second diffracted light detecting unit, wherein the first light distribution unit includes a ninth region and a tenth region, wherein The light diffracted by the ninth area of the first light distribution means is output as third diffracted light, and the tenth area of the first light distribution means is included in the reflected light reflected by the optical disk. The light diffracted by the optical disc is output as a fourth diffracted light, and among the reflected light reflected by the optical disc, the light is diffracted separately from the first diffracted light by the first region of the first light distribution means. The fifth light is output as a fifth diffracted light, and the light diffracted separately from the second diffracted light by the second region of the first light distribution means out of the reflected light reflected by the optical disc is Sixth
The second diffracted light detection means outputs the eleventh region and the twelfth region.
, A thirteenth area, a fourteenth area, a fifteenth area, and a sixteenth area, and the eleventh area is provided with a seventh sub-diffraction light detecting means, Eighth in the area
, A ninth sub-diffraction light detection means is provided in the thirteenth area, a tenth sub-diffraction light detection means is provided in the fourteenth area, and a fifteenth area is provided. Is provided with an eleventh sub-diffraction light detection means, a twelfth sub-diffraction light detection means is provided in a sixteenth area, and the third diffraction light is provided with the seventh sub-diffraction light detection means and The eighth sub-diffracted light detecting means detects the fourth diffracted light, and the fourth diffracted light is detected by the eleventh sub-diffracted light detecting means and the twelfth sub-diffracted light detecting means. Is detected by the tenth sub-diffracted light detecting means and the eleventh sub-diffracted light detecting means, and the sixth diffracted light is detected by the eighth sub-diffracted light detecting means and the ninth sub-diffracted light detecting means. Means, the control device, the seventh And the amount of diffracted light detected by the ninth sub-diffracted light detecting means, the ninth sub-diffracted light detecting means, and the eleventh sub-diffracted light detecting means. 2. The optical disc apparatus according to claim 1, wherein a focus error signal of the optical disc is obtained based on a difference between an amount of diffracted light detected by the sub-diffracted light detection means and the twelfth sub-diffraction light detection means. 22. The apparatus according to claim 22, further comprising a second diffracted light detecting means, wherein the first light distribution means includes a ninth area and a tenth area, wherein The light diffracted by the ninth area of the first light distribution means is output as third diffracted light, and the tenth area of the first light distribution means is included in the reflected light reflected by the optical disk. The light diffracted by the optical disc is output as a fourth diffracted light, and among the reflected light reflected by the optical disc, the light is diffracted separately from the first diffracted light by the first region of the first light distribution means. The fifth light is output as a fifth diffracted light, and the light diffracted separately from the second diffracted light by the second region of the first light distribution means out of the reflected light reflected by the optical disc is Sixth
The second diffracted light detection means outputs the eleventh region and the twelfth region.
, A thirteenth area, a fourteenth area, a fifteenth area, and a sixteenth area, and the eleventh area is provided with a seventh sub-diffraction light detecting means, Eighth in the area
, A ninth sub-diffraction light detection means is provided in the thirteenth area, a tenth sub-diffraction light detection means is provided in the fourteenth area, and a fifteenth area is provided. Is provided with an eleventh sub-diffraction light detection means, a twelfth sub-diffraction light detection means is provided in a sixteenth area, and the third diffraction light is provided with the seventh sub-diffraction light detection means and The eighth sub-diffraction light detecting means detects the fourth diffracted light, and the fourth diffracted light is detected by the eighth sub-diffraction light detecting means and the ninth sub-diffraction light detecting means.
The tenth sub-diffraction light detecting means and the first
And the sixth sub-diffraction light detecting means,
The diffracted light of the eleventh sub-diffraction light detecting means and the first
And the control device is detected by the seventh sub-diffraction light detection means, the ninth sub-diffraction light detection means, and the eleventh sub-diffraction light detection means. And the amount of diffracted light detected by the eighth sub-diffracted light detecting means, the tenth sub-diffracted light detecting means, and the twelfth sub-diffracted light detecting means. 2. The optical disk apparatus according to claim 1, wherein a focus error signal of the optical disk is obtained by using the optical disk apparatus.