JP3377334B2 - Optical head device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION The present invention relates to an optical disc or an optical disc.
Recording information on optical or magneto-optical media such as cards
.Relating to optical head devices that perform reproduction or erasure
is there. [0002] 2. Description of the Related Art As a high-density and large-capacity storage medium,
Optical memory technology using an optical disk having a pattern
Are digital audio discs, video discs,
Document file discs and even data files
Applications are expanding. In this optical memory technology, information
Is highly precise to the optical disc through a minutely focused light beam.
It is recorded and reproduced with certainty and reliability. This recording / playback operation
Depends solely on the optical system. The main part of the optical system is an optical head device.
The basic function is to create a diffraction-limited small spot.
Light, focus control and tracking control of the optical system, and
And the detection of the cut signal. These features are
Depending on the purpose and application, various optical systems and photoelectric conversion detection methods
It is realized by a combination. In particular, in recent years, optical head devices have been reduced in size and thickness.
In order to achieve this, an optical head device using a hologram has been disclosed.
Have been. A first conventional optical head device will be described below.
An example will be described with reference to FIGS. In addition,
In the xyz coordinates displayed at the lower left of each figure, the same coordinates
The axes indicate the same direction on the drawing. FIG. 18 shows a side of a first conventional optical head device.
FIG. This optical head device includes a semiconductor laser 10
1, photodetector 190, collimating lens 102,
Hologram element 170, objective lens 103, optical disk
105. The emitted light L0 from the semiconductor laser 101 is
The hologram element is collected by the re-
The light passes through the element 170 and enters the objective lens 103. Soshi
Focus on the optical disk 105 by the objective lens 103
Is done. The light beam reflected by the optical disk 105 is originally
Traverses the optical path of
You. Return light diffracted light L1 generated by hologram element 170
Is incident on the photodetector 190 and detected. This light detection
By calculating the output of the device 190, the servo signal and
And an information signal. [0008] Hologram element 170 and photodetector 19
FIG. 19 shows the detailed configuration of the two, and their mutual arrangement. Figure
19 is the negative direction of the z-axis (the optical disk 105
From the direction toward the semiconductor laser 101).
FIG. 2 shows a plan view of a system element 170 and a photodetector 190. FIG.
In the figure, it is shown at the top and bottom in the figure, but actually
Are located inside the hologram element 170 in the positional relationship on the y-axis.
The center coincides with the center of the photodetector 190, and
Looking at them, they should overlap. But the detailed structure
For easier understanding, FIG. 19 shows the hologram element 1
70 is shown shifted by a predetermined distance in the y-axis direction.
You. For the same reason, the size of the hologram element 170 is not
The dimensions of the photodetector 190 are enlarged. hologram
The element 170 has three regions 1 having different hologram patterns.
70a, 170b, and 170c. Also
The detection areas of the photodetector 190 are areas S2a, S1b, S1.
a, S1c, S1b ', S1a', S1c 'and S2b
Is divided into [0009] The area 170a is formed by the hologram element 170.
Two types of spheres with different curvatures for the + 1st-order diffracted light on the return path that passes through
It is designed to be a surface wave. First and second types
Of the photodetector 190 (z-axis)
From above the paper surface, that is, from the detection surface of the photodetector 190.
This is a position close to the hologram element 170 away from the
To the front side) and the back side (on the z-axis, below the page)
Side, that is, a hologram remote from the detection surface of the photodetector 190
Position far from the ram element 170,
Side)), and both spherical waves are
Each light beam on the surface of the photodetector 190 shown in FIG.
Incident on the cross sections L1a and L1a 'indicating the spots of the
You. The focus error signal FE indicates the focus position.
Known SSD (spot size detection
Method) method. That is, the focus error signal F
E represents the output value by the sign of each detection area,
It is obtained by the operation of (Equation 1). FE = (S1a−S1b−S1c) − (S1a′−S1b′−S1c ′) (Formula 1) Region 170b and region 170 of hologram element 170
c is transmitted through the region S2 of the photodetector 190, respectively.
a and S2b. Truck
Error signal TE is detected by the push-pull method.
You. The tracking signal TE is detected by each of the photodetectors 190.
Expressing the output value with the sign of the area, the operation of (Equation 2)
Obtained by TE = S2a-S2b (2) In the configuration of the first conventional example described above, the semiconductor laser 101
The photodetector 190 is located close to the
Can be realized. A second prior art example is shown in FIGS.
I will explain while. The xy displayed at the lower left of each figure
In the z coordinate, the same coordinate axis indicates the same direction. In FIG. 20, this optical head device is diffracted.
Grating 111, collimating lens 102, hologram
System element 170, objective lens 103, and optical disk 105
Have. The optical head device further includes an optical head according to the present invention.
LD-PD whose structure is shown in Fig. 2 that is commonly used with
Module (Laser Diode Photo Detector Module)
Joule) 114. In FIG.
The joule 114 is a silicon substrate 204, a silicon substrate 2
Semiconductor laser 101 and silicon substrate fixed to 04
204 has photodetectors 191 and 192 formed on the surface thereof.
I do. The silicon substrate 204 is etched
A mirror 205 is formed and the semiconductor laser 101
Outgoing light emitted in the y-axis direction from the
5, the light beam is reflected in the z-axis direction of the silicon substrate 204.
The light is emitted as the data L0. Therefore, the light beam L0 is in the z-axis direction.
The light is emitted from the apparent light emitting point 101A in the direction. In FIG. 20, the outgoing light L0 is
11 to detect tracking error signal
A pair of sub-beams (not shown) are formed. Next
Then, these lights pass through the hologram element 170 and
The light enters the lens 103 and is focused on the optical disk 105.
You. The light beam reflected by the optical disk 105 is
Follow the original optical path in reverse and enter the hologram element 170
I do. ± 1 next time return path from hologram element 170
Origami (L1, L2) are each LD-PD module
The light enters the photodetectors 191 and 192 in the 114 and is detected
Is done. Calculate the outputs of photodetectors 191 and 192
The focus error signal FE and the tracking
Servo signal and information signal including the error signal TE are obtained.
It is. Hologram element 170 and LD-PD module
The detailed configuration of the module 114 is shown in FIG. FIG.
Is the negative direction of the z-axis in FIG.
From the disk 105 to the LD-PD module 114
Hologram element 170 and LD-PD module
FIG. In FIG. 21, the upper part in the figure
Are shown side by side at the bottom, but actually, the positional relationship on the y-axis
Then, the center of the hologram element 170 is the LD-PD module.
The center of the rule 114, and when viewed from the z-axis direction.
Both should overlap, but the detailed structure is easy to understand
In FIG. 21, the hologram element 170 is
The direction is shifted by a predetermined distance in the drawing. Also the same reason
For the reason, the LD-PD
The dimensions of the module 114 have been increased. The hologram element 170 is a hologram element shown in FIG.
Fresnel consisting of a single region with a program pattern
It is a zone plate. Figure 21 shows an LD-PD module
114, the apparent light emitting point 101A of the semiconductor laser 101
And the positional relationship between the photodetectors 191 and 192
I have. The detection surface of the photodetector 191 includes regions S1a, S1b,
It is divided into S1c, S3a and S3b. Photo detector
The detection surface 192 includes the areas S2a, S2b, S2c, and S4a.
And S4b. In FIG. 20, the hologram element 170
The diffracted lights L1 and L2 are respectively separated by the photodetector 191 and
192. The surface of the photodetectors 191 and 192
The cross section of the light beam at the circles L1a, L1b, L
1c, L2a, L2b, L2c.
Here, the cross sections L1a and L2a are spots by the main beam.
Is represented. Also, the cross sections L1b, L1c, L2b and
L2c represents a spot by the sub beam. The hologram element 170 has a Fresnel zone
The diffraction light L1 is
Forward to the apparent light emitting point 101A (positive direction of z axis,
(Vertically above the paper). Further, the diffracted light L2 is
(The negative direction of the z-axis). The focus error signal FE is at this convergence position.
Detection is carried out by a known SSD method utilizing a difference in arrangement. One
The focus error signal FE is output from the photodetectors 191, 1
When the output value is represented by the sign of each detection area of 92,
It is obtained by the calculation of the above (Equation 3). FE = (S1a−S1b−S1c) − (S2a−S2b−S2c) (3) On the other hand, the tracking error signal TE is a known three-beam
Detect by method. That is, the tracking signal TE is
When the output value is represented by the sign of each detection area, the following (Equation 4)
Is obtained. TE = (S3a + S4a) − (S3b + S4b) (4) [0022] SUMMARY OF THE INVENTION The structure of the first conventional example is described.
The result is a + 1st-order diffracted light generated from the hologram element 170.
Is divided into focus error signal and tracking error
The signal is getting both. Therefore, using the -1st order diffracted light
The light use efficiency is low. For example, when the output of the light source is small,
Light reflectance is low, and the optical transmission efficiency of the optical system is low.
If the information is not
Signal output, the optical output on the information medium is kept low.
Light usage efficiency is low when it is necessary to
Then, the ratio of noise to signal (S / N ratio) becomes low. Further, the offset of the circuit system (for example,
Width offset) due to temperature change or aging change
When it changes, a large offset occurs in the servo signal.
There is a problem that there is a possibility of producing. Further, in this configuration, the cross sections L1a and L1
a 'for detecting the focus error signal FE incident on
The tracking error signal TE is detected for the light beam
Light in the areas 170b and 170c for
You. As a result, the linearity of the focus error signal is
There has been a problem of causing deterioration of the servo characteristics. Further, the tracking error signal TE is
Detected only by the light beam in a partial area of the gram element 170
Is unstable if there is a scratch on the disc.
There was also a problem that it was. In the second conventional example, the configuration shown in FIG.
Of the LD-PD module 114
Offset to focus error signal FE
Exists. This forms the etching mirror 205.
Therefore, a concave portion is provided in the silicon
Light emitted from the semiconductor laser 101 by the mirror 205
The apparent light emitting point 101A is
The surface of the recon board 204, that is, the photodetectors 191 and 1
Shift backward (negative z-axis direction) with respect to plane 92
Becomes On the other hand, generated by the hologram element 170
Diffracted lights L1 and L2 are substantially equal to + z
Light having a focus separated by a distance equal to the direction and -z direction
Becomes Therefore, due to the aforementioned shift of the light emitting point, the photodetector
On the surfaces 191 and 192, the light beams L1 and L2
The spot size is different and the spot size obtained by (Equation 1)
The focus error signal does not become zero at the time of focusing. As described above, the optical head having this configuration has an offset
Focus servo stability and, consequently, signal
There is a problem of causing deterioration. Further, the tracking error signal TE detection
Because the secondary beam is generated on the outward path,
Enough for recording / reproducing heads that require light intensity on the disk surface
There is also a problem that the light intensity cannot be secured. Further, in the second conventional example, the three-beam method
Is used to detect the tracking error signal TE.
Therefore, a pair of auxiliary beams is required. For this reason, optical
The light intensity of the main beam on the disk surface decreases. Special
In addition, the recording / reproducing optical head requires a large light intensity on the disk surface.
This is important, and it is difficult to use the optical head having this configuration. According to the present invention, the servo characteristics are stable,
An object of the present invention is to provide an efficient optical head. [0034] An optical head device according to the present invention.
Is a radiation source that emits a light beam; and
Beam of light converges to a small spot on the information medium
A condensing optical system, and diffracts the light reflected by the information medium to generate +
Simultaneous generation of nth-order diffracted light and -nth-order diffracted light (n: natural number)
Hologram element and diffraction by the hologram element
Multiple light detectorsdetectionHas a photodetector consisting of
The radiation source is fixed to the photodetector, and
The emission point of the radiation source is out of the plane of the photodetector,Said
The hologram element has a first pattern region different from the first pattern region.
A portion in which regions of the second pattern are alternately arranged;
Different from the first and second patterns and different from each other
The third pattern area and the fourth pattern area are alternately arranged.
Having a placed portion, The light detector includes the hologram
Each diffracted in the area of the plurality of patterns of the device
Detects focus error signal by receiving + nth order diffracted light
Focusing error detector and the plurality of patterns
Receiving the respective -n-order diffracted lights diffracted in the region
Tracking error detection to detect racking error signal
Has a dispatcher, + N emanating from the area of the first pattern
Next diffracted light leaves the plane of the focus error detector
Converges to a position farther from the hologram element (hereinafter referred to as a rear position)
And -n order diffraction emanating from the region of the first pattern
Light is incident on the first area of the tracking error detector
And + N order diffraction emanating from the area of the second pattern
The light is holographically separated from the plane of the focus error detector.
Converges to a position close to the
-N-order diffracted light emitted from the area of the second pattern is
Incident on the first area of the racking error detector, Previous
The + n-order diffracted light emitted from the region of the third pattern is:
Converges to a position behind the focus error detector,
The −n-order diffracted light emitted from the area of the pattern No. 3
Incident on a second region of the king error detector; and The said
The + n-order diffracted light emitted from the area of the pattern No. 4
And converges to a position in front of the focus error detector.
-N-order diffracted light emitted from the pattern area is tracked
Incident on the second region of the error detector,+ Nth order
Focus using only all (n: natural number) diffracted light
An error signal is detected, and all of the -n order (n: natural number) are detected.
Tracking error signal using only the diffracted light
It is characterized by that. [0035] [0036] [0037] [0038] [0039] [Action] (1) Focusing is performed using all of the + n-order diffracted light beams.
Signal strength, the signal strength is large and the signal-to-noise ratio is high.
A focus error signal with a high (S / N) can be obtained.
Wear. Also, for the same reason, focus error signal detection
Focus error with high sensitivity,
-Signal can be obtained. In the present invention, the luminous flux of the -n-th order diffracted light is
The tracking error signal is obtained using all
Tracking with high strength and high signal-to-signal ratio (S / N)
Error signal can be obtained. Also the same reason
Stable signal detection even if there is a scratch on the disc
Can be. [0041] [0042] (3) Forming based only on the + n-order diffracted light
Hologram element design to obtain focus error signal
Light emitting point 101B and light detection surface of LD-PD module
The problem of deviation from the above is solved. Therefore, the LD-PD module
Can be used without focus offset.
You. Therefore, the size and weight of the optical head device can be reduced, and
Cost reduction and stability improvement. [0045] DESCRIPTION OF THE PREFERRED EMBODIMENTS The xyz coordinates shown at the lower left of each drawing below
In the drawings, the same coordinate axis indicates the same direction. [First Embodiment] First, a first embodiment of the present invention is described.
An example optical head device will be described with reference to the drawings.
You. FIG. 1 shows an optical head device according to a first embodiment of the present invention.
FIG. In FIG. 1, LD-PD
The module 114 converts the xyz coordinates shown in the lower left of the figure.
arranged so as to emit light L0 polarized in the x-axis direction.
I have. The collimating lens 102 flattens the output light L0.
Make a line ray. Transmits polarized light in a specific direction and is orthogonal to it
Polarization anisotropy holo that has the function of diffracting polarized light in different directions
Gram 181 is arranged to transmit polarized light in the x-axis direction.
Have been. Quarter-wave plate 115, objective lens 103,
The polarization anisotropic hologram 181 is
It is held in a predetermined positional relationship. Optical disk 105
The tangent direction at the light beam irradiation point matches the y direction
Are arranged as follows. The holding means 116 is a driving means 11
2 driven. First, the LD-PD module 114 and
The polarization anisotropic hologram 181 will be described below.
You. FIG. 2 shows a general LD-PD module 1.
It is a perspective view showing the structure of No.14. In FIG. 2, LD-
The PD module 114 includes a silicon substrate 204 and a silicon
The semiconductor laser 101 fixed in the concave portion of the substrate 204,
Photodetector 19 formed on the surface of silicon substrate 204
1, 192. In addition, the silicon substrate 204
With an etching mirror 205 formed on the wall of the recess
And the emission radiated from the semiconductor laser 101 in the y-axis direction.
Light is etched by the mirror 205 to the silicon substrate 20.
Then, the light beam L0 is reflected above the surface 4 and the light beam L0 is emitted. The LD-PD module 1 having such a configuration
In 14, the semiconductor laser 101 as a light emitting source
Directly on the silicon substrate 204 on which the devices 191 and 192 are formed.
Because the contact is fixed, the change in the positional relationship is caused by the temperature change.
It is stable and is not easily affected by vibrations and the like. In addition,
Laser 101 is placed in a concave portion on the surface of silicon substrate 204.
Since it is surface mounted, its mounting accuracy is good and mass production
It has an easy structure. FIG. 3 shows a polarization anisotropic hologram 181.
It is sectional drawing of the element formed. Lithium niobate group on x-plane
A groove 209 having a depth da is formed at regular intervals on the surface of the plate 207.
It is formed by notching. Professional in this groove 209
A ton exchange area 208 is formed. The polarization anisotropy of the device having the above structure
The operation of the hologram 181 will be described below. Different polarization
Part of the light incident on the isotropic hologram 181 is proton
The other light is transmitted through the exchange area 208 and the groove 209,
It passes through the lithium butyrate substrate 207. As a result,
The phase of light transmitted through the ion exchange region 208 is lithium niobate.
The phase of the light transmitted through the memory substrate 207 is shifted. When ordinary light enters, the proton exchange region 2
In 08, the refractive index drops by 0.04,
Phase advances in the exchange area 208 and further increases in the groove 209.
The phase advances. On the other hand, when extraordinary light enters,
The exchange region 208 increases the refractive index by 0.145 and
There is a delay. However, in the groove 209, the leading of the phase occurs.
Cancel each other out of phase. Thus, the proton exchange region 2
08 and the depth of the groove 209 are appropriately selected.
Polarization separator, where ordinary light is diffracted and extraordinary light is not diffracted
Noh can be realized. For example, a light field having an incident wavelength of 0.78 μm
In order to realize the polarization separation function, the depth da of the groove 209 is required.
Is 0.25 μm, and the depth dp of the proton exchange region 208 is
Should be set to 2.22 μm. The groove 209 is optional.
Can be divided into areas, and takes an arbitrary pattern in the plane
be able to. As a result, to obtain an arbitrary wavefront of diffracted light
Can be. The operation of the optical head device having the above configuration will be described.
explain about. Output from LD-PD module 114
Light L0 is collimated by collimating lens 102
It is converted into a luminous flux. This light is polarized in the x-axis direction.
Without diffracting the polarization anisotropic hologram 181
To Penetrate. This light is circularly polarized by the 波長 wavelength plate 115.
Into the objective lens 103, and the optical disk 10
5 is collected. Optical beam reflected by optical disk 105
Traverses the original optical path to the quarter-wave plate 115
Incident, converted into y-polarized light, and polarized anisotropic hologram
Incident on the beam 181. The reconstruction generated from the polarization anisotropic hologram 181
+ 1st order diffracted light (L1) and -1st order diffracted light (L2)
Are the photodetectors 191 and 194 in the LD-PD module 114.
And 192, respectively. This light to multiple areas
Detection is performed by the divided photodetectors 191 and 192, and the detection is performed.
By calculating the output signal, the servo signal and
And obtain an information signal. The polarization anisotropic hologram 181 and the LD-
The relationship between the PD modules 114 will be described with reference to FIG.
I will tell. FIG. 4 shows the negative direction of the z-axis in FIG.
From the optical disk 105 to the LD-PD module 114
Polarization hologram 181 and L
FIG. 3 shows a plan view of the D-PD module 114. In FIG.
Are shown side by side at the top and bottom in the figure.
In the above positional relationship, the center of the polarization anisotropic hologram 181
Coincides with the center of the LD-PD module 114,
When viewed from the z-axis direction, both should overlap, but detailed
A certain distance in the y-axis direction to facilitate understanding of the structure
The figure is shifted only. Also for the same reason, polarization anisotropic
LD-PD module for the size of the hologram 181
The dimensions of the knob 114 are enlarged. Polarized anisotropic hologram
The system 181 has the pattern shown in FIG. FIG.
Is the semiconductor laser 101 of the LD-PD module 114.
The apparent light emitting point 101A, the light detector 191 and the light detector
The positional relationship with the output device 192 is shown. LD-PD module
The detection surface of the photodetector 191 of the module 114 is parallel to the x-axis.
Band-shaped areas S1b, S1a, S1c, S1b ', S1
a 'and S1c'. Also, the photodetector 192
Are two regions S2a and S2a by a line parallel to the y-axis.
2b. As shown in FIG.
181 is divided into a plurality of band-shaped regions parallel to the y-axis.
I have. This area basically consists of four patterns
And the arrangement of each pattern is hatched in the figure.
Are displayed according to the type. The first pattern in the area 181a is
The light incident on the area 181aAs + 1st order diffracted lightKolime
After passing through the switching lens 102, the surface of the photodetector 191
Position away from the polarization anisotropic hologram 181 away from
(Negative direction of z-axis, hereafter referred to as “rear position”)
Bundles and enters the position indicated by the cross section L1a of the light beam
It is designed to be. At this time, the primary
Is diffracted to the position indicated by the cross section L2a of the light beam.
Polarized anisotropic hologram 181 away from plane of output unit 192
(Positive direction of z-axis, hereinafter referred to as “front position”)
Incident) while converging. That is, the light beam is light
Hit a semi-circular area on the surface of the detector 191 or 192
You. The second pattern in the area 181b is
The light incident on the area 181b isAs + 1st order diffracted lightKolime
After passing through the switching lens 102, the surface of the photodetector 191
Converges to a position in front of (in the positive direction of the z-axis), and the section L1
It is designed to be incident on the position indicated by b. this
At the same time, the -1st-order diffracted light generated simultaneously is indicated by the cross section L2b.
The position behind the plane of the photodetector 192 to the position
Incident while converging in the negative direction). The third pattern in the area 181c is
The light incident on the area 181c isAs + 1st order diffracted lightKolime
After passing through the switching lens 102, the surface of the photodetector 191
Converges to a position behind (in the negative direction of the z-axis), and the region L1
It is designed to be incident on the position indicated by c. this
At the same time, the −1st-order diffracted light generated simultaneously is indicated by the region L2c.
The position in front of the plane of the photodetector 192 to the position
Incident while converging in the positive direction). The fourth pattern in the area 181d is
Area 181dLight incident onAs + 1st order diffracted lightKolime
After passing through the switching lens 102, the surface of the photodetector 191
Converges to a position in front of (in the positive direction of the z-axis), and the section L1
It is designed to be incident on the position indicated by d. this
At the same time, the −1st-order diffracted light generated simultaneously is indicated by the region L2d.
The position behind the plane of the photodetector 192 to the position
Incident while converging in the negative direction). The information signal, tracking error signal,
The detection of a focus error signal will be described below. The information signal is supplied to photodetectors 191 and 192
Can be obtained by summing the detection outputs of Also, information
The report signal is the sum of the detection outputs of the photodetector 191 or the photodetection.
It can also be obtained only by the sum of the detection outputs of the output unit 192.
Noh. The latter method uses the LD-PD module 114
This is effective when the number of outputs is limited. Next, a method for detecting a tracking error signal
Will be described. In this configuration, the polarization anisotropic hologram
The beam 181 is diffracted by the regions 181a and 181b.
The next diffracted light enters the area S2b of the photodetector 192.
It is designed to be. Also, the regions 181c and 181d
The -1st-order diffracted light diffracted at is incident on the region S2a.
It is designed to be. Of the polarization anisotropic hologram 181
The design is made with the depth da of the groove 209 of the lithium niobate substrate.
By appropriately setting the depth dp of the proton exchange region,
It is done. The tracking error signal TE is
It can be detected by the pull method. Tracking error
The signal TE is the sign of each detection area of the photodetector 192.
When the output value of is expressed, it can be obtained by the following calculation of (Equation 5).
Can be TE = S2a-S2b (Equation 5) Next, a method of detecting the focus error signal FE will be described.
You. The focus error signal FE is
The known SSD method for detecting the size of each light spot
Detected. The focus error signal FE is
When the output value is represented by the code of each detection area 91,
(Equation 6). FE = (S1a−S1b−S1c) − (S1a′−S1b′−S1c ′) (6) The focus error signal FE is given by the following (Equation 7).
By operation using only the output values of the areas S1a and S1a '
Is also obtained. FE = S1a−S1a ′ (7) The calculation of equation (7) is performed by the output of the LD-PD module 114.
When the number is limited or the signal in the pit row is focused
This is effective when you want to reduce the effect on the error signal.
You. The detailed operation will be described below with reference to FIG.
You. FIG. 5 is a plan view of the photodetector 191. FIG. FIG. 5A shows the state on the optical disk 105 (FIG.
Optical detection in the focused state where the light beam is converged in 1)
It is a top view of the output device 191. Semicircular cross sections L1a, L1c
Is located behind the detection surface of the photodetector 191 (minus the z-axis).
The light beam to be focused in the direction
1 shows a cross section of a light beam when the light beam strikes a first detection surface. cross section
The cross-sectional areas of L1a and L1c are substantially equal. Also, the cross section L1
b and L1d are respectively focused in front of the photodetector 191 to perform photodetection.
14 shows a cross section of a light beam impinging on a detection surface of the output device 191.
You. The cross-sectional areas of the cross sections L1b and L1d are substantially equal. Follow
The focus error obtained by (Equation 6) or (Equation 7).
The signal FE becomes substantially zero. In FIG. 1, the optical disk 105 is
When the camera approaches the lens 103 and becomes defocused,
As shown in FIG. 5B, interruption of the light beam on the photodetector 191 is performed.
The surfaces L1a and L1c are focused on the photodetector 191.
Since it is farther away, it becomes larger on the photodetector 191. So
As a result, the output value of the area S1a decreases, and the areas S1b, S1b
The output value of 1c increases. Conversely, the cross sections L1b and L1d
Since the focusing position approaches the photodetector 191,
It becomes smaller on the output device 191. As a result, the region S1a '
Increases, and the output values of the regions S1b 'and S1c'
Decrease. Therefore, the file obtained by (Equation 6) or (Equation 7)
The focus error signal FE becomes negative. FIG. 5C shows that the optical disk 105 is
Light indicating a defocused state that has moved away from the lens 103
FIG. 9 is a plan view of a detector 191. The cross sections L1a and L1c are
Since the focus position of the light beam approaches the photodetector 191,
It becomes smaller on the detector 191. As a result, the region S1a
Output value increases, and the output values of the regions S1b and S1c decrease.
You. Conversely, the cross sections L1b and L1d are the focusing positions of the light beams.
Moves away from the photodetector 191 and on the photodetector 191
growing. As a result, the output value of the area S1a 'decreases,
The output values of the areas S1b 'and S1c' increase. Therefore,
(Equation 6) Focus error signal FE obtained by (Equation 7)
Is positive. As described above, in this configuration, the focus error
A signal can be obtained. Note that this configuration
Splits the light beam in the x-axis direction to obtain a signaling error signal
are doing. However, the splitting direction and the polarization anisotropy hologram 18
1. The main diffraction directions (x-axis direction in FIG. 4) are matched.
Therefore, the influence on the focus error signal can be ignored. In this embodiment, the detection of the photodetector 191 is performed.
The plane is divided parallel to the x-axis. In addition, photodetectors
A tracking error signal was obtained on the detection surface 192.
Between sections L2c and L2a and between sections L2d and L2b
The distance in the x-axis direction is made sufficiently large. Also, light detection
The lengths of the devices 191 and 192 in the x-axis direction are represented by cross sections L1a.
L1d and L2a to L2d are sufficiently larger than the length in the x-axis direction.
I'm strong. Therefore, the wavelength fluctuation of the semiconductor laser 101
Even if each spot moves in the x-axis direction, the light beam
There is no possibility that the pot will protrude from the detection area. Further, this configuration is similar to that of the semiconductor laser 101.
Even if the light emitting point 101B shifts in the x-axis direction, the detection signal has no effect.
The purpose is to avoid receiving it. The LD-PD module 114 shown in FIG.
In the manufacturing process, a semiconductor laser is
101 needs to be fixed. In this fixing process, semiconductor
Position while observing the laser 101 from above (z-axis)
Decide. At this time, the emission point 10 of the semiconductor laser 101
1B is on a plane perpendicular to the y-axis. Therefore, this surface is
If the light emitting point 101B is positioned at a predetermined position,
Above can be positioned correctly. However, the light emitting point 101B
Is not necessarily at the center of the semiconductor laser chip
Is shifted by cutting. Therefore, the outer shape of the chip
Accurate positioning in the x-axis direction based on
Can not. Therefore, in the x-axis direction,
This occurs. In this embodiment, as described above, the photodetector 19
2, make the length in the x-axis direction sufficiently larger than the length of each cross section.
Therefore, the shift of the light emitting point 101B in the x-axis direction is
In the same way as the displacement of the light beam spot
It does not affect the robot signal. As described above, in this embodiment, the + 1st order diffracted light
The focus error signal using all the light beams
And traps using all the -1st-order diffracted light beams.
Since a king error signal can be obtained, the signal strength
Large servo signals with high signal-to-noise ratio (S / N)
Obtainable. Further, the beam is used by using all the + 1st-order diffracted light beams.
Focus error signal.
In the y-axis direction (the photodetector 19)
No unevenness in the light intensity (in the direction perpendicular to the dividing line 1)
A good focus error signal can be obtained. Further, all the light amounts of the −1st order diffracted light are used.
The tracking error signal can be obtained by
For example, even if there is a scratch on the disc,
I can go out. As described above, in this embodiment, the first conventional example
Can solve all the problems. In this embodiment, L which is a problem in the related art
Focus offset section of D-PD module 114
It is also effective in solving the problem. The problem of this offset is that the hologram element
Take the diffraction angle of 170 appropriately large and use collimating
Using the fact that the principal plane of the lens 102 is spherical, the solution
There is a way to decide. However, this method
The grating pitch of the hologram element 170 used is several μm or less
And there is a problem in mass productivity. Further, it is used in the first embodiment of the present invention.
Such a polarization anisotropic hologram 181 has such fine details.
The grid pitch cannot be realized, and this method solves the problem.
Is impossible. For this reason, in the first embodiment, the + 1st-order diffraction
Two wavefronts converging to different positions as light are detected by a photodetector
191 equidistant and independently in the opposite direction (on the z axis)
Using a polarization anisotropic hologram 181 as formed
I have. The position on the z-axis between the light emitting point 101B and the photodetector surface
When the LD-PD module with a different
It can be used without any data. As a result, stable
Focus servo becomes possible. Further, in the configuration of the first embodiment, the second
Unlike the previous example, the secondary
No beam is needed. Therefore, the light intensity on the disk surface
There is also an effect that it can be sufficiently secured. Thus, the first implementation
According to the example, all the problems of the second conventional example can be solved. In the first embodiment, the LD-
Good stability because of using PD module 114
An optical system can be manufactured at low cost. In general, an optical head using a hologram element
Are LD (laser diode) and PD (photodetector)
Module). This module
In this case, the semiconductor laser and the photodetector are close and firmly fixed.
Misalignment due to thermal expansion, vibration, etc.
Is less likely to occur and a stable operation can be realized. On the other hand, these
Obtain a module with special adjustment of the positional relationship between elements.
Was difficult and the production cost was high. However, the LD-PD module of the first embodiment
In the module 114, the photodetectors 191 and 192 are connected in the same series.
Since the photodetector 191 and the photodetector 191 are formed on the
The relative position of the output device 192 is determined by an integrated circuit manufacturing process.
Easy setting to high accuracy, for example, on the order of submicrons
You. Further, mounting of the semiconductor laser 101 is also
It can be mounted from the surface of the control board 204. That is, 1
Can be done from the axial direction. Therefore, for example, when changing workpieces
It can be mounted with high accuracy without errors such as displacement. In the first embodiment, for example, the focus offset
The problems of the LD-PD module 114 such as
While using the LD-PD module 114.
Therefore, an optical system with good stability can be obtained at low cost. Further, according to the first embodiment, as described above,
In the x-axis direction of the light emitting point 101B of the semiconductor laser 101,
Greater tolerance for misalignment, lower cost and better stability
An optical system is obtained. Further, in the first embodiment, the polarization anisotropic hollow
Gram 181 combined with quarter-wave plate 115
Therefore, unnecessary diffraction does not occur on the outward path. Return trip
Generates diffracted light to obtain servo signals, etc.
You. Therefore, the light use efficiency is high and the signal amplitude is large.
Furthermore, there is no noise due to unnecessary diffracted light, and very S /
A signal with a high N ratio can be obtained. Especially compact
For optical discs with higher density than discs
In the optical head device used, unnecessary diffracted light is reduced
By approaching to zero, more accurate servo signals and
There is a remarkable effect that an information signal can be obtained. Further, the diffraction efficiency of +1 order and −1 order on the return path
And lower the zero-order diffraction efficiency (transmittance)
Therefore, the amount of light returning to the semiconductor laser 101 can be reduced.
I can do it. Therefore, a semiconductor laser as a radiation source
In the case of using
The generation of coup noise can be avoided. Further, in the first embodiment, the polarization anisotropic hollow
Gram 181, quarter-wave plate 115 and objective lens 10
3 while maintaining a certain relative position by the holding means 106
I support it. Therefore, for tracking control,
When the lens 103 moves, the polarization anisotropic hologram 18
1 also moved together and reflected from the optical disk 105
The light beam almost moves on the polarization anisotropic hologram 181.
Does not work. Therefore, the movement of the objective lens 103 is not affected.
Not obtained from the photodetectors 191 and 192
Signal does not deteriorate at all and stable servo control is possible. The polarization anisotropic hologram 181 of the first embodiment
Are a number of strips parallel to the y-axis as shown in FIG.
It is divided into regions. In this configuration,
Since there is only one kind of grating, unnecessary due to interference between gratings
No significant diffracted light is generated, and stray light is reduced. Ma
In addition to reducing noise, the light use efficiency is high. Further, the polarization anisotropic hologram 181
The pattern is used to track the focus error signal.
Care to minimize signal leakage
Have been. That is, the focus is on the rear side of the surface of the photodetector 191.
Focus on the area (181a and 181c) connecting
Alternate the area (181b and 181d) a sufficient number of times
In the plane of the polarization anisotropic hologram 181 by repeatedly disposing
In the intensity distribution of the light beam at the detector gives the detection signal
The impact is mitigated. That is, each section L1a, L1
b, the light beam reaching L1c or L1d is polarized anisotropic
Light coming from a plurality of band-shaped regions of the hologram 181
A collection of beams. Therefore, the polarization anisotropic hologram 1
81, the distribution of the intensity of the light beam incident on the plane 81 is not uniform.
And even if partial unevenness occurs, the sections L1a, L1
b, the unevenness of the average light intensity between L1c and L1d is reduced.
You. As a result, the cross sections L1a, L1b, L1c and L1d
The intensity of the -1st order diffracted light that is mixed into the light beam of
And the output value due to the mixed -1st order diffracted light is given by
6) or by subtraction of (Equation 7). as a result
The aforementioned leakage of the tracking signal is reduced. In the first embodiment, the polarization anisotropic hollow
As the gram 181, the one shown in FIG. 3 is used. Different polarization
The anisotropic hologram 181 has a diffraction effect on the polarization direction.
Hologram elements having different rates may be used. For example, JP
A hologram element having a structure disclosed in JP-A-3-314502.
Is also good. A hologram element using liquid crystal may be used. Further, the LD-PD module 114 is
Limited to the LD-PD module having the structure shown in FIG.
No, the laser diode and the photodetector are integrated
What is necessary is just a D-PD module. For example, in FIGS.
The LD-PD module shown may be used. LD- in FIG.
PD module is silicon substrate 204, silicon substrate 2
Photodetectors 191 and 19 provided at both ends of the surface
2. A table provided at the center of the surface of the silicon substrate 204
A surface-emitting type semiconductor laser 117 is provided. Surface radiation
Type semiconductor laser 117 is provided by a built-in reflection mirror.
Laser light emitted in the y-axis direction
Is reflected in the direction perpendicular to the surface of the
Emit. The LD-PD module shown in FIG.
Is the LD-PD module shown in FIG.
Different from le. The surface emitting semiconductor laser 118 is
Emit laser light L0 in a direction perpendicular to recon board 204
You. In this embodiment, a method of detecting each signal by ± 1st-order diffracted light is used.
The method was explained. However, the diffracted light is ± 1st order diffracted light
The diffraction is not limited to ± n order (n is a natural number)
Each signal can be detected by light. [Second Embodiment] An optical head device of a second embodiment
Will be described. Compared to the optical head device of the first embodiment
Tracking error to the focus error signal
-If signal leakage suppression is necessary,
The head is valid. The basic structure of the optical head device according to the second embodiment is as follows.
This is the same as the first embodiment shown in FIG. The first embodiment and
The difference from the second embodiment is that the hologram pattern shown in FIG.
The polarization anisotropic hologram 182 having
It is used instead of the program 181. Again
The operation is substantially the same as in the first embodiment. The polarization anisotropic hologram 182 has a 182a
And 182b. The region 182a is a cross section of FIG.
Simultaneous light corresponding to light having L1a and L2b respectively
Designed to occur. Also, the region 182b
Corresponds to light having cross sections L1c and L2d respectively in FIG.
It is designed to generate light at the same time. These regions 182a and 182b are basically
The superposition of two different Fresnel zone plates
It is composed of With such an optical head
Is diffracted light having a focal point on the front side of the surface of the photodetector 191.
Diffracted light with a focal point on the rear side is almost
Emanating from the surface. Therefore, the track of the optical disc 105
Is equal to the diffracted light in the areas 182a and 182b
Mixed in. However, the diffracted light of the regions 182a and 182b
The value detected by the diffracted light evenly mixed into the
Substantially offset by subtraction. Therefore, the obtained focus error signal
Noises such as tracking error signal leakage
A small and stable focus servo can be realized. Especially
Suppression of tracking signal leakage into focus error signal
This is an effective configuration when the pressure is important. In the second embodiment, there is no need for interference between gratings.
Diffracted light is generated, except for that.
Has all the lengths. In the second embodiment, the polarization anisotropy shown in FIG.
Hologram 182 is a polarization anisotropic hologram shown in FIG.
Hologram with different diffraction efficiency for the polarization direction
Any gram element may be used. For example, JP-A-63-3145
02 may be a hologram element having the structure disclosed in
May be used as a hologram element. Further, the LD-PD module 114 is
Using an LD-PD module having the structure shown in Fig. 2
Not as long as the. Integrated semiconductor laser and photodetector
LD-PD module that is
And the LD-PD module shown in FIG. [Third Embodiment] The light beam of the third embodiment of the present invention is shown in FIG.
The head device is a semiconductor device compared to the optical head device of the first embodiment.
Accuracy is required to adjust the position of the body laser 101 in the y-axis direction.
However, it is said that the focus error signal detection sensitivity is good.
Has features. Therefore, the third embodiment uses focus servo control.
When it is necessary to perform strictly, for example, the focus of the objective lens
This is effective when the depth is shallow. The basic configuration and operation of the third embodiment are similar to those of the third embodiment.
This is the same as the first embodiment. FIG. 9 shows the z-axis in FIG.
Negative direction (from the optical disc 105 on the paper to the LD-PD
Polarization anisotropy in the direction toward module 114).
Plan view of the program 183 and the LD-PD module 114
Is shown. In FIG. 9, it is shown side by side at the top and bottom in the figure.
However, in actuality, the polarization anisotropy hollow
The center of Gram 183 is in LD-PD module 114
Coincides with the heart, and when viewed from the z-axis direction,
However, in order to make the detailed structure easier to understand, y
The drawing is shifted by a predetermined distance in the axial direction. Again
For the same reason, L for the dimension of the polarization anisotropic hologram 183
The dimensions of the D-PD module 114 have been enlarged. No.
The difference between the first embodiment and this embodiment is that the hologram shown in FIG.
The polarization anisotropic hologram 183 having a pattern is
It is used in place of the anisotropic hologram 181. Also
Photodetectors 191 and 1 of LD-PD module 114
92 is divided into regions shown in FIG. As shown in FIG. 9, a polarization anisotropic hologram
183 passes through the center of the hologram element and is aligned with the x-axis and the y-axis.
With two parallel straight lines, four regions 183a,
183b, 183c and 183d. Each territory
Transmit through regions 183a, 183b, 183c, 183d
Light is applied to the cross sections L1a, L1b, L1c, and L1d, respectively.
Therefore, the light enters the position shown. Polarized anisotropic hologram 18
3 is a case where the light beam is focused on the optical disc 105.
In this case, each light is set to be focused on the photodetector 191.
Is being measured. The polarization anisotropic hologram 183 is
The -1st-order diffracted light represented by the cross sections L2a and L2b is the photodetector 1
92 and enters the region S3b and is represented by cross sections L2c and L2d.
The -1st-order diffracted light enters the region S3a of the photodetector 192.
It is designed to be. The information signal is supplied to the photodetectors 191 and 192
From the sum of the detected values of Optical inspection
Sum of detection outputs of the output unit 191 or the photodetector 192
It is also possible to obtain the information signal only by the sum of the detection values of
is there. In the latter case, the number of outputs of the LD-PD module 114 is
Effective when limited. Next, the tracking error due to this configuration
A signal detection method will be described. Polarized anisotropic hologram
The beam 183 is diffracted by the regions 183a and 183b.
The next diffracted light enters the area S3b of the photodetector 192,
The -1st order diffracted light diffracted in the regions 183c and 183d is
It is designed to be incident on the region S3a. others
The tracking error signal TE is calculated using the push-pull method.
Can be detected more. This tracking error signal TE is used for each detection.
The output values are indicated by the signs of the output areas S3a and S3b.
And the following equation (8). TE = S3a−S3b (Equation 8) Next, a method of detecting the focus error signal FE will be described.
You. The focus error signal is known on the photodetector 191.
(Not shown). Four
Each detection area S1a, S1b, S2 of the spill error signal FE
When the output value is represented by the signs of a and S2b, the following (expression)
It is obtained by the operation of 9). FE = (S1a + S2a) − (S1b + S2b) (Equation 9) When the focus error signal FE is detected by (Equation 9),
In this case, since the regions S1a and S2a are adjacent to each other,
It can be used without being divided as a region. The focus error signal FE is
Regions S1a and S1 by (Expression 10) or (Expression 11)
b, or by calculation using the regions S2a and S2b.
Can be FE = S1a-S1b (Equation 10) FE = S2a-S2b (Equation 11) This calculation is performed when the number of outputs of the LD-PD module 114 is limited.
It is effective when it is set. Below, the detailed operation
This will be described with reference to FIG. FIG. 10 shows the distribution of light on the photodetector 191.
It is a top view for explaining a state. FIG. 10A shows the light
Focused state where light beam is focused on disk 105
FIG. 4 is a diagram showing a light distribution state in the case of FIG. Section L1a, L
1c is on the boundary between the regions S1a and S1b, and the light
Focusing on top. The cross sections L1b and L1d correspond to the region S2a.
It is on the boundary of S2b, and the light is focused on it. Follow
To obtain the equation obtained by (Equation 9), (Equation 10) or (Equation 11).
The focus error signal FE becomes substantially zero. FIG. 10B shows an optical disk 105, for example.
Is too close to the objective lens 103 and defocused
FIG. 14 is a plan view of the photodetector 191 when the light detection is performed. Section L1
a and L1c are in the area S1b and do not exist in the area S1a.
No. That is, light is incident on the region S1b and is incident on the region S1a.
Does not enter. The cross sections L1b and L1d are in the region S2b.
Not in the area S2a. That is, light enters the area S2b.
And does not enter the region S2a. Therefore, (Equation 9),
Focus error obtained by (Equation 10) or (Equation 11)
The signal FE becomes negative. FIG. 10C shows, for example, the optical disk 105.
Moves away from the objective lens 103 and becomes defocused.
FIG. 9 is a plan view of the photodetector 191 when the light is detected. Section L1
a and L1c are in the area S1a but not in the area S1b. You
That is, light enters the region S1a and enters the region S1b.
do not do. Further, the cross sections L1b and L1d are in the region S2a.
And is not in the area S2b. That is, light is applied to the region S2a.
The incident light does not enter the region S2b. Therefore, (Equation 9),
Focus error obtained by (Equation 10) or (Equation 11)
The signal FE becomes positive. As described above, in the configuration of the third embodiment,
It is possible to obtain a sparse error signal. This configuration
Changes the light beam by x to obtain a tracking error signal.
Although split in the axial direction, the polarization direction differs from the split direction of the light beam.
The main diffraction directions of the isotropic hologram 183 are matched.
Therefore, the influence on the focus error signal can be ignored. In the third embodiment, a light beam is detected.
Detector 191 is divided into strips parallel to the x-axis.
Have been. Further, the detection surface of the photodetector 192 in FIG.
, Between the cross section L2b and L2d of each light beam and the cross section
The distance between L2a and L2c is made sufficiently large. Also optical inspection
The length of the light sources 191 and 192 in the x-axis direction is
It is sufficiently larger than the size of the cross section. Therefore, semiconductor laser
The position of the light beam in the x-axis direction due to the wavelength fluctuation of the laser 101
Does not affect the detection of each signal. Further, this configuration is similar to that of the semiconductor laser 101.
The effect of the displacement of the light emitting point 101B in the x-axis direction can be eliminated.
The purpose is. The details have been described in the first embodiment.
To manufacture the LD-PD module 114, as shown in FIG.
It is necessary to fix the semiconductor laser 101 to the recon board 204
There is. In this fixing step, the semiconductor laser 101 is moved in the y-axis direction.
Direction, accurate positioning is possible by observing the end face.
Wear. However, in the x-axis direction, the outer shape of the semiconductor laser 101 is
Even if it is observed, it is difficult to perform high-precision positioning. Therefore small
A large position error is inevitable. In this embodiment, the light detector 192 in the x-axis direction
Let the length be the cross section L2a, L2b, L2c and L2 of the light beam.
d, the light emission point in the x-axis direction
The deviation is similar to the deviation due to the above-mentioned wavelength fluctuation in the servo signal.
Has no effect. As described above, in this embodiment, the + 1st order diffracted light
A focus error signal can be obtained using all of the light flux
it can. In addition, by using all the light beams of the -1st-order diffracted light,
Signal can be obtained, so the signal strength is high.
To obtain a servo signal with a high signal-to-noise ratio (S / N)
Can be. Further, all the -1st-order diffracted light beams are used.
To obtain a tracking error signal.
Even if there is a scratch on the disc, signal detection is stable.
There is also an effect that can be cut. As described above, in the third embodiment,
All the problems of the first conventional example can be solved and the effect is great.
No. Further, in this embodiment, L which is a conventional problem
Focus offset section of D-PD module 114
It is also effective in solving the problem. The problem of this offset is that the hologram element
Take the diffraction angle of 170 appropriately large and use collimating
Using the fact that the principal plane of the lens 102 is spherical, the solution
There is a way to decide. However, the hologram used in this method
The lattice pitch of the memory element 170 becomes several μm or less, which leads to mass productivity.
There's a problem. Further, the polarization difference as used in this embodiment is
Such a grid pitch cannot be realized with an isotropic hologram.
Therefore, it is impossible to solve the problem by this method. For this reason, in this embodiment, + 1st-order diffracted light is used.
To form a plurality of wavefronts converging on the photodetector 191
Using the light anisotropic hologram 183, the light emitting point and the light detection surface
Different LD-PD modules are
It can be used in the state without it. To this
More stable focus servo becomes possible. Further, the configuration of this embodiment is the same as that of the second prior art.
Unlike the tracking error signal detection,
No light is needed and sufficient light intensity on the optical disk surface can be secured.
There is also an effect that can be cut. As described above, according to the present embodiment,
All the problems of the conventional example 2 can be solved. In this embodiment, as described above, the LD-PD
Because the module 114 can be used, the stability
A good optical system can be manufactured at low cost. Generally, an optical head using a hologram element
Uses a module in which an LD and a PD are integrated. this
In the module, the semiconductor laser and photodetector are close and strong
It is fixed firmly, and it is misaligned due to thermal expansion, vibration, etc.
Is less likely to occur and a stable operation can be realized. On the other hand, these
Adjusting the elements to a specific positional relationship to make them modular
It was difficult and the production cost was high. However, the LD-PD module 114
The light detector 191 and the light detector 192 are the same silicon base.
Since the light detector 191 and the light detector 1 are formed on the plate 204,
Easier relative position to 92 by integrated circuit fabrication process
For example, it can be set to high accuracy on the order of submicrons. Further, the semiconductor laser 101 is mounted on the surface.
Because it can be mounted and can be made from one axis direction, for example,
Accurate mounting without errors such as displacement when changing
It has such a feature. In this embodiment, focus offset and the like
To solve the problem of LD-PD module 114
To obtain an optical system with good stability at low cost
Becomes Furthermore, according to the present embodiment, the semiconductor
The deviation tolerance of the body laser emission point in the x-axis direction is large.
An inexpensive and stable optical system can be obtained. Further, in this embodiment, the polarization anisotropic holographic
183 and the quarter-wave plate 115 are used in combination.
Therefore, unnecessary diffraction does not occur on the outward path. On the way back
Then, diffracted light for generating a servo signal or the like is generated. Obedience
Therefore, the efficiency of light utilization is high, the signal amplitude is large, and
No noise due to necessary diffracted light and very high S / N ratio
A signal can be obtained. In particular, compact discs
Optical disk for higher density optical discs
In an optical device, unnecessary diffraction is further reduced to near zero.
To provide higher quality servo and information signals.
There is a remarkable effect that can be obtained. Further, in the configuration of this embodiment, +1 of the return path is used.
The diffraction efficiencies of the 0th and -1st orders are increased, and
Excess) can be reduced, so that the semiconductor laser 10
The amount of light returning to 1 can be reduced. Therefore, synchrotron radiation
When a semiconductor laser is used as the source, return light and output light
Avoids the occurrence of scoop noise due to interference
There is a clear effect. Further, in this embodiment, the polarization anisotropic hologram
183, quarter-wave plate 115 and objective lens 103
Is held at a certain relative position by the holding means 106.
Provided. Therefore, for example, for tracking control
When the objective lens 103 moves, the polarization anisotropic hologram
183 also moves together and reflects from the optical disk 105
Most of the light beam is polarized on the polarization anisotropic hologram 183.
Do not move. Therefore, the movement of the objective lens 103 causes
Therefore, the signals obtained from the photodetectors 191 and 192 are all
A stable servo without deterioration is possible. The polarization anisotropic hologram 183 of the third embodiment
Has only one type of grid at one location. Therefore interstitial
Unnecessary diffracted light is not generated by the interference of
Reduces noise, reduces noise, and increases light use efficiency.
The effect is that In this embodiment, the polarization anisotropy hologram was used.
The ram 183 was a polarization anisotropic hologram shown in FIG.
However, the polarization anisotropic hologram 183
Any hologram element having a different diffraction efficiency may be used. For example,
Hologram having the structure disclosed in Japanese Unexamined Patent Publication (Kokai) 63-314502
It may be an element or a hologram element using liquid crystal. The LD-PD module 114 is
The LD-PD module shown in Fig. 4 was used.
The semiconductor laser and photodetector are integrated
Any LD-PD module may be used.
Good as the LD-PD module shown in FIGS. 6 and 7
No. In this embodiment, a method of detecting each signal by ± 1st-order diffracted light is used.
The method was explained. However, the diffracted light is ± 1st order diffracted light
The diffraction is not limited to ± n order (n is a natural number)
Each signal can be detected by light. [Fourth Embodiment] Optical Head Device of Fourth Embodiment
Will be described with reference to FIG. In the first to third embodiments
In this case, the information signal is detected by the photodetectors 191 and 192.
Derived from the sum of power. In the fourth embodiment, an information signal is optically detected.
It can be detected by one area of the output device 192.
Therefore, only one head amplifier for information signal detection is sufficient.
There is a feature that. An optical head device having this configuration is, for example,
If the noise of the head amplifier becomes a problem,
Effective when expensive broadband head amps cannot be used
It is. The basic configuration and operation of the fourth embodiment are similar to those of the fourth embodiment.
This is the same as the first embodiment. FIG. 11 is a diagram of FIG.
Axis negative direction (LD-P
Polarization anisotropy in the direction toward D module 114)
Plane of hologram 181 and LD-PD module 114
The figure is shown. FIG. 11 shows the upper and lower parts in the figure side by side.
However, in practice, the position on the y-axis
The center of the hologram 181 is the LD-PD module 114
And when viewed from the z-axis direction, they overlap.
But to make the detailed structure easier to understand
2 is shown shifted by a predetermined distance in the y-axis direction.
Also, for the same reason, the dimensions of the polarization anisotropic hologram 181 are reduced.
On the other hand, the dimensions of the LD-PD module 114 are enlarged.
I have. The difference between the first embodiment and this embodiment is that the LD-PD module
The photodetector 191 of the module 114 is, as shown in FIG.
Divided into comb-shaped areas S1a, S1b, S1c, S1d
Have been. The comb-shaped regions S1a and S1c are
It is engaged with the mold regions S1b and S1d. Photodetector 1
92 is not divided. First, the polarization anisotropic hologram 181 and the LD
FIG. 11 is used for the relationship with the PD module 114.
Will be described. FIG. 11 shows a polarization anisotropic hologram 181.
And the LD-PD module 11
4 and the photodetectors 191 and 19
2 shows a positional relationship with the second position. As shown in the figure,
The anisotropic hologram 181 is the same as that used in the first embodiment.
Are the same. With this configuration, the tracking error signal
Detection is performed by the push-pull method. Tracking signal
TE represents the output value by the sign of each detection area.
It is obtained by the operation of (Equation 12). TE = (S1a + S1b)-(S1c + S1d) (12) The focus error signal FE is detected by the SSD method.
You. The focus error signal FE is a sign of each detection area.
The output value can be expressed by the following (Equation 13).
Can be FE = (S1a + S1c)-(S1b + S1d) (Equation 13) The feature of the fourth embodiment is that the information signal detection is performed in a single area optical detection.
This is to be performed by the output unit 192. For this reason, photodetectors
Just amplify the 192 detection signal with one head amplifier
Good, no problem of accumulation of head amp noise
Information signals can be detected. With the above noise accumulation
Means the phenomenon described below. That is, multiple detection areas
Detection signals from each are amplified by multiple head amplifiers
Then, a plurality of amplified signals are added to form one output signal.
Then, the noise of each head amplifier is accumulated in the output signal.
The S / N ratio deteriorates. Also, as described above, the information signal light
Since the detector 192 is independent, the head amplifier
Amplify only the signal band.
And low noise compared to a head amplifier that can amplify
Things can be used. In the fourth embodiment, the optical head of the first embodiment is used.
It also has the features of the storage device. Polarization Anisotropic Hologram in Fourth Embodiment
181 is a polarization anisotropic hologram shown in FIG.
The polarization anisotropic hologram 181 diffracts light in the polarization direction.
Any hologram element having different efficiencies may be used. For example,
Hologram element having structure disclosed in JP-A-63-314502
Alternatively, a hologram element using liquid crystal may be used. Further, the LD-PD module 114 is
The LD-PD module having the structure shown in FIG.
Not limited, semiconductor laser and photodetector are integrated
Any LD-PD module, such as FIG.
The LD-PD module shown in FIG. 7 may be used. Further, instead of the polarization anisotropic hologram 181,
In addition, for example, the polarization anisotropic hologram used in the second embodiment
182 may be used. [Fifth Embodiment] The optical head device of the fifth embodiment
Can detect the information signal by one area
You. Therefore, one head amplifier for information signal detection
There is a feature that is good. The optical head device of this configuration is
For example, if the noise of the head amplifier is a problem,
When expensive broadband head amps cannot be used
It is valid. In the fifth embodiment, the optical head of the fourth embodiment is used.
In this case, the adjustment accuracy in the y-axis direction is required as compared with the storage device. Only
Focus error signal detection sensitivity
If you need to perform focus servo strictly,
This is effective, for example, when the focal depth of the objective lens is shallow.
You. The basic configuration and operation of this embodiment are the same as those of the third embodiment.
This is the same as the embodiment. FIG. 12 is a view along the z-axis in FIG.
In the negative direction (from the optical disc 105 to the LD-
Polarization anisotropy in the direction toward PD module 114)
Between the hologram 181 and the LD-PD module 114
FIG. In Fig. 12
Although shown, in actuality, the polarization anisotropic
Of the hologram 181 is the LD-PD module 11
4 and both are heavy when viewed from the x-axis direction.
It should be, but to make the detailed structure easier to understand
2 is shown shifted by a predetermined distance in the y-axis direction.
For the same reason, the size of the polarization anisotropic hologram 181 is not
The size of the LD-PD module 114 is enlarged.
You. The difference between the third embodiment and this embodiment is that the LD-PD module
The photodetector 191 of the ruler 114 is arranged as shown in FIG.
It is divided into areas. The photodetector 191 has a rectangular shape.
A detection region S1a, a U-shaped region S1b surrounding the detection region S1a, and
The square region S1c and the U-shaped region S1d surrounding it
Has been split. Photodetector 192 is not split. First, the polarization anisotropic hologram 183 and L
FIG. 12 shows the relationship with the D-PD module 114.
It will be described using FIG. FIG. 12 shows a polarization anisotropic hologram 18.
3 and the LD-PD module 1
14 light emitting points of the semiconductor laser 101 and the photodetector 191
FIG. 14 is a diagram showing a positional relationship between the light detector 192 and the light detector 192.
As shown in the figure, the polarization anisotropic hologram 183 is
This is the same as the polarization isotropic hologram used in the embodiment.
You. With this configuration, the tracking error signal
Detection is performed by the push-pull method. Tracking signal
TE represents the output value by the sign of each detection area.
(Equation 14). TE = (S1a + S1b)-(S1c + S1d) (14) The focus error signal FE is detected by the knife edge method.
Put out. The focus error signal FE is a code of each detection area.
When the output value is expressed by the symbol, the operation of the following (Equation 15) is performed.
Obtained by FE = (S1a + S1c) − (S1b + S1d) (15) The feature of the fifth embodiment is that the information signal detection is performed in a single area optical detection.
This is to be performed by the output unit 192. For this reason, photodetectors
Just amplify the 192 detection signal with one head amplifier
With no problem of head amplifier noise accumulation.
Good information signals can be detected. In addition, information signal detection
Since the output unit is independent, the head amplifier
Amplify only the frequency of the conventional servo
Cheaper than a head amplifier that can amplify up to the frequency of the band
And low noise ones can be used. In the fifth embodiment, the optical head of the third embodiment is used.
It also has the features of In the present embodiment,
The optically anisotropic hologram 183 is a polarization anisotropic hologram shown in FIG.
The polarization anisotropy hologram 183 is
If the hologram element has different diffraction efficiency in the light direction,
Good. For example, the structure disclosed in JP-A-63-314502.
Hologram element may be used, and a hologram using liquid crystal
It may be an element. Also, the LD-PD module 114
Was an LD-PD module having the structure shown in FIG.
However, this is not the case, and the semiconductor laser and photodetector are integrated
Any LD-PD module may be used.
Good as the LD-PD module shown in FIGS. 6 and 7
No. [Sixth Embodiment] FIG. 13 shows the light of the sixth embodiment.
FIG. 3 is a side view illustrating a configuration of a head device. The light of this embodiment
The optical device comprises a quarter-wave plate 115 and a polarization anisotropic hologram.
System element 181 is separated from the objective lens 103.
You. However, the polarization anisotropic hologram 181 and the LD-PD
Each element part itself such as the joule 114 is the first to fifth components.
The description in the embodiment can be applied. Therefore, in the configuration of the present embodiment, the traffic
Locking error signal TE and focus error signal FE
Is obtained in the same manner as in the first to fifth embodiments.
Of course. The structure of the sixth embodiment is similar to that of the
When it is necessary to reduce the thickness, for example, a thin optical head
This is effective when conversion is required. Note that the hologram element is a polarization anisotropic element.
The case where the hologram 181 is used has been described.
Not just. Polarization anisotropy holograms 181 to 183
Even if used, the photodetectors 191 and
The photodetector 192 may be divided into regions. In the sixth embodiment, a polarization anisotropic hologram
The system 181 uses the polarization anisotropic hologram shown in FIG.
You. However, the polarization anisotropic hologram 181
Any hologram element having a different diffraction efficiency may be used. An example
For example, a hologram having a structure disclosed in JP-A-63-314502.
Gram element or hologram element using liquid crystal
Good. The LD-PD module 114 is shown in FIG.
Used an LD-PD module with a
LD-PD module with integrated laser and photodetector
For example, the LD-PD model shown in FIGS.
It may be joule. [Seventh Embodiment] FIG. 14 is a diagram showing a light source according to a seventh embodiment.
FIG. 2 is a side view showing a configuration of the pad device. The seventh embodiment is the sixth
LD-PD module 114 of the embodiment, collimating
Glens 102, polarization anisotropic hologram 181 and 1 /
This is a configuration in which the four-wavelength plate 115 is integrated. One optical system
, The mutual positional relationship is positive.
And a stable optical system can be realized. This module can be used to connect various shapes of light.
Can be used as a common component of
The cost of the storage device can be reduced. In this embodiment, the hologram element is used.
The case where a polarization anisotropic hologram 181 is used is shown.
However, this is not the only case, and the polarization anisotropic hologram 181 is used.
183 also correspond to the photodetectors 191 and 19.
2 may be divided into predetermined regions. In this embodiment, the polarization anisotropy hologram was used.
The ram 181 was a polarization anisotropic hologram shown in FIG.
However, the polarization anisotropic hologram 181
Any hologram element having a different diffraction efficiency may be used. For example,
Hologram having the structure disclosed in Japanese Unexamined Patent Publication (Kokai) 63-314502
Element or a hologram element using liquid crystal.
No. The LD-PD module 114 is shown in FIG.
LD-PD module with the structure
LD with integrated semiconductor laser and photodetector
-Any PD module, for example, as shown in FIGS.
LD-PD module may be used. [Eighth Embodiment] FIG. 15 is a sectional view showing an optical system according to an eighth embodiment.
FIG. 2 is a side view showing a configuration of the pad device. The optical head of this embodiment
Is the polarization anisotropic hologram 181 of the sixth embodiment.
Is collimated with the LD-PD module 114.
It is arranged between the lens 102. In this configuration, the polarization anisotropic hologram 18
1 is arranged close to the LD-PD module 114
Therefore, further stabilization of the optical head can be realized. Sa
In addition, the diameter of the polarization anisotropic hologram 181 is small.
And cost reduction can be realized. In this embodiment, the hologram element is used.
Shows the case where the polarization anisotropic hologram 181 is used.
However, this is not the case. For example, polarization anisotropic hologram
The light detectors 191 corresponding to each of the
And the photodetector 192 may be divided into regions. Also book
In the configuration of the embodiment, the quarter-wave plate 115 is, for example, a collimator.
Lens 102 and polarization anisotropic hologram 181
It is also possible to arrange it between. However, in this embodiment, the polarization anisotropy hologram was used.
The ram 181 was a polarization anisotropic hologram shown in FIG.
However, the polarization anisotropic hologram 181
Any hologram element having a different diffraction efficiency may be used. For example,
Hologram having the structure disclosed in Japanese Unexamined Patent Publication (Kokai) 63-314502
Element or a hologram element using liquid crystal.
No. The LD-PD module 114 is shown in FIG.
LD-PD module with the structure
LD with integrated semiconductor laser and photodetector
-Any PD module, for example, as shown in FIGS.
LD-PD module may be used. [Ninth Embodiment] FIG. 16 is a diagram showing a light source of this embodiment.
FIG. 2 is a side view showing a configuration of the pad device. In the present embodiment, the eighth
Example LD-PD Module 114 and Polarized Anisotropic Hollow
Gram 181 and frame member 141A are integrated.
There are two modules. Therefore, a stable optical system
realizable. In addition, this module can
Can be used as a common component of
The cost of the head can be reduced. In this embodiment, the hologram element is used.
Shows the case where the polarization anisotropic hologram 181 is used.
However, this is not the only case, and the polarization anisotropic hologram 18
1 to 183 can also be used. In this case, each
Is divided into regions corresponding to the photodetectors 191 and 192.
Just do it. In this configuration, the quarter-wave plate 115 is
Collimating lens 102 and polarization anisotropic hologram
181. In addition,
In the configuration of the collimating lens 102 or 1 /
It is also possible to integrate the four-wavelength plate 115 together.
Also, a collimating lens 102 and a １ ／ wavelength plate
115 can be integrated. This configuration
And collimating lens 102 and objective lens 103
It is also possible to replace with one lens. In the ninth embodiment, a polarization anisotropic hologram was used.
181 used the polarization anisotropic hologram shown in FIG.
Is a hologram element with different diffraction efficiency for the polarization direction
I just need. For example, it is disclosed in JP-A-63-314502.
A hologram element with a closed structure may be used.
It may be a gram element. Also, LD-PD module
Reference numeral 114 denotes an LD-PD module having the structure shown in FIG.
However, this is not the case. Semiconductor laser and photodetector
Any LD-PD module that integrates
For example, the LD-PD module shown in FIGS. 6 and 7
It is good. The embodiments of the present invention have been described above.
However, in all these configurations,
17 and the quarter-wave plate are replaced, for example, by the element shown in FIG.
It is also possible to reduce the size and weight. FIG. 17 shows a 波長 wavelength plate and a polarization anisotropic hologram.
It is a multifunctional element having a function of gram. Constitution
Is on the back surface of the part having the polarization anisotropic hologram function,
For example, tantalum pentoxide (Ta) which is a birefringent film_TwoO_Five) Slope
In this case, a deposited film is formed. Polarized anisotropic hologram
Orthogonal to each other at an angle of 45 degrees with the polarization of the
When a polarized light is transmitted, a phase difference of 1/4 wavelength occurs.
The thickness is determined so that. A multifunctional device like the one above
By using this, the size and weight of the optical head device can be reduced.
it can. Further, in all of the above embodiments, the bias
Instead of optically anisotropic holograms, partially transmit and partially
Non-polarized or hologram with small polarization anisotropy that diffracts
A configuration using an element and omitting the 1/4 wavelength plate is also feasible
It is. [0173] As described above, according to the optical head device of the present invention,
Then, there are mainly the following effects. (1) Using all the luminous fluxes of the + 1st-order diffracted light
Since a focus error signal can be obtained,
High focus, high signal-to-noise ratio (S / N)
An error signal can be obtained. For the same reason, the focus error signal
The intensity distribution of the diffracted light for detection is uniform, and the sensitivity is high.
An focus error signal can be obtained. In the optical head device of the present invention, the -1
Obtains a tracking error signal using all the amount of folding light
Signal strength and signal-to-noise ratio
It is possible to obtain a tracking error signal with a high (S / N)
it can. For the same reason as above, scratches on the disc
Signal can be detected stably even when there is (2) In the optical head device of the present invention, the information signal
Signal detection is performed by a single area photodetector,
Just amplify the detector signal with one head amp
No. Noise accumulation when using multiple head amplifiers
It is possible to detect a good information signal without any problem. In addition, the detector for the information signal is independent.
Therefore, the head amplifier amplifies only the information signal band.
Often, the bandwidth of the head amplifier can be limited. Therefore,
Less expensive than a head amplifier that can amplify up to the servo band of
Therefore, a low noise type can be used. (3) The optical head device of the present invention has a +1 order
To obtain a focus error signal using only the diffracted light,
The light emitting point of LD-PD module
Focus offset even if there is a shift between
It can be used in the state without a set. Therefore, the optical head
The device can be made smaller, lighter, lower in cost and more stable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of an optical head device according to a first embodiment of the present invention; FIG. 2 is a perspective view of an LD-PD module; FIG. FIG. 4 shows a polarization anisotropic hologram and LD-P of the first embodiment.
FIG. 5A is a plan view showing a positional relationship between D modules. FIG. 5A shows a photodetector 191 in a state where a light beam is focused on an optical disk in the first embodiment.
FIG. 13B is a plan view of the photodetector 191 in the defocus state where the objective lens approaches the optical disc in the first embodiment.
FIG. 4C is a plan view of the photodetector 19 in the defocused state where the objective lens has moved away from the optical disk of the first embodiment.
FIG. 6 is a perspective view of an LD-PD module of another example. FIG. 7 is a perspective view of an LD-PD module of another example. FIG. 8 is a perspective view of an optical head device according to a second embodiment of the present invention. FIG. 9 is a plan view showing a positional relationship between a polarization anisotropic hologram and an LD-PD module according to a third embodiment of the present invention. FIG. In the example, the light detector 19 in a state where the light beam is focused on the optical disc is shown.
FIG. 1B is a plan view of the photodetector 191 in the defocused state in which the objective lens approaches the optical disc in the third embodiment.
FIG. 7C is a plan view of the photodetector 1 according to the third embodiment in a defocused state where the objective lens has moved away from the optical disc.
FIG. 11 is a plan view showing a positional relationship between a polarization anisotropic hologram and an LD-PD module of an optical head device according to a fourth embodiment of the present invention. FIG. 12 is a plan view showing light according to a fifth embodiment of the present invention. FIG. 13 is a plan view showing a positional relationship between a polarization anisotropic hologram of a head device and an LD-PD module. FIG. 13 is a side view of an optical head device according to a sixth embodiment of the present invention. FIG. FIG. 15 is a side view of an optical head device according to an eighth embodiment of the present invention. FIG. 16 is a side view of an optical head device according to a ninth embodiment of the present invention. FIG. 18 is a cross-sectional view of a hologram composite element. FIG. 18 is a side view of an optical head device of a first conventional example. FIG. 19 is a plan view showing a positional relationship between a hologram element and a photodetector of the optical head device of the first conventional example. FIG. 20 is a side view of an optical head device of a second conventional example. FIG. 21 is a second conventional example. Plan view illustrating the positional relationship between the hologram element and the photo detector of the optical head device. DESCRIPTION OF SYMBOLS 101 Semiconductor laser 102 Collimating lens 103 Objective lens 105 Optical disk 111 Diffraction grating 114 LD-PD module 115 Quarter wave plate 116 Holding means 117 Surface emitting laser 170 Hologram element 181 Polarized anisotropic hologram 182 Polarized light Anisotropic hologram 183 Polarized anisotropic hologram 190 Photodetector 191 Photodetector 192 Photodetector 204 Silicon substrate 205 Etching mirror 207 Lithium niobate substrate 208 Proton exchange region 209 Groove 210 Tantalum pentoxide (Ta ₂ O ₅ ) film

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiaki Kanma 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Hidehiko Wada 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-2-58738 (JP, A) JP-A-4-53031 (JP, A) JP-A-3-178064 (JP, A) JP-A-8-22624 (JP, A) WO 93/9535 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B ^7/ 09-7/22

Claims (1)

(57) [Claim 1] A radiation light source that emits a light beam, a light-collecting optical system that receives the light beam from the radiation light source and converges to a minute spot on an information medium, and the information medium A hologram element for diffracting the light reflected by the hologram element to simultaneously generate + n-order diffraction light and -n-order diffraction light (n: natural number), and a photodetector comprising a plurality of detection regions for detecting the light diffracted by the hologram element. The radiation light source is fixed to the photodetector, the emission point of the radiation light source is out of the plane of the photodetector, and the hologram element is arranged in a different first pattern area.
A region where the region and the region of the second pattern are alternately arranged;
Different from the first and second patterns and different from each other
The third pattern area and the fourth pattern area alternate
And the photodetector includes a plurality of patterns of the hologram element.
+ N-order diffracted light diffracted in the
Focusing error to detect focus error signal
Detector, and that diffracted in the area of the plurality of patterns
Receiving each -nth order diffracted light, a tracking error signal
+ N-order diffracted light emitted from the region of the first pattern having a tracking error detector for detecting
But a hologram away from the plane of the focus error detector
Converges to a position farther from the element (hereinafter referred to as a rear position),
-N-order diffracted light emitted from the area of the pattern 1
+ N-order diffracted light incident on the first area of the racking error detector and emitted from the area of the second pattern
Is a hologram away from the plane of the focus error detector
Converges to a position close to the element (hereinafter, a forward position),
-N-order diffracted light emitted from the area of pattern 2
+ N-order diffracted light that is incident on the first area of the locking error detector and emanates from the area of the third pattern
Converges to a position behind the focus error detector and
The -n-order diffracted light emitted from the region of the third pattern is
Incident on the second area of the racking error detector and before
The + n-order diffracted light emitted from the region of the fourth pattern is
Converge in front of the position of the focus error detector, the first
The n-th order diffracted light emitted from the area of the pattern No. 4
It is incident on the second region of the king error detector, detects a focus error signal using only all the diffracted lights of the + n order (n: natural number), and detects all the focus error signals of the -n order (n: natural number). An optical head device for detecting a tracking error signal using only diffracted light.