JP3842364B2 - Optical head device for optical disc player - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical head device used in an optical disc player for performing information reproduction and / or recording processing on an optical disc.
[0002]
[Prior art]
An optical disk player is used to optically read and reproduce information recorded on the optical disk and to optically record information on the optical disk. This type of optical disc player has a turntable for rotationally driving the optical disc, and an optical head device for irradiating the optical disc on the turntable with a light beam and taking in a reflected light beam from the optical disc.
[0003]
In the optical head device, the reflected light beam from the optical disk is guided to one or a plurality of photodetectors and converted into an electrical signal. Based on the electrical signal thus obtained, not only the reproduction of information on the recording surface of the optical disc but also the tracking control and focusing control of the light spot formed on the recording surface are performed. Here, the tracking control is a control for aligning the light spot and the track on the recording surface, and the focusing control is a control for forming an image of the light spot on the recording surface. Normally, tracking control and focusing control are performed using different photodetectors.
[0004]
In this type of photodetector, the positioning setting is important in order to align the detection region with the incident reflected light beam. At this time, in the conventional optical head device, for example, as disclosed in Japanese Patent Application Laid-Open No. 4-167232 (Japanese Patent Application No. 2-293861), the optical axis direction (Z direction) of the reflected light beam and the optical axis direction are perpendicular to each other. The position of the photodetector is adjusted in two axial directions (X and Y directions) perpendicular to each other in a flat plane.
[0005]
[Problems to be solved by the invention]
That is, in the conventional optical head device described above, the position of the photodetector is adjusted in all three axis directions. Such position adjustment makes it possible to position the photodetector with high accuracy. However, it takes time for the adjustment work, and the position of the photodetector is likely to be shifted due to changes in conditions such as temperature after the adjustment. Have a problem.
[0006]
The present invention has been made in view of such a problem. Focusing on a photodetector (focus PD) for performing focusing control, and improving the support mechanism, the position adjustment operation of the focus PD can be performed in a short time. It is possible to provide an optical head device for an optical disc player, which can be performed at the same time and is less likely to cause a position shift of the focus PD after position adjustment.
[0007]
[Means for Solving the Problems]
A first aspect of the present invention is an optical head device of an optical disc player,
A detection surface including two detection regions arranged in parallel along the first direction across a reference line extending in a second direction perpendicular to the first direction, and a light spot on the recording surface of the optical disc A photodetector used for focusing control to form an image;
A wavefront splitting optical element for splitting a reflected light beam traveling from the optical disc along the third direction to the photodetector into first and second beam portions that project onto the two detection regions, respectively.
Support for supporting the photodetector so that the position of the detection surface can be adjusted only in two axial directions perpendicular to each other in a plane parallel to the third direction and intersecting the first direction. Mechanism,
It is characterized by comprising.
[0008]
A second aspect of the present invention is an optical head device of an optical disc player,
A detection surface divided into first to fourth detection areas by first and second reference lines extending and intersecting in first and second directions perpendicular to each other, and forming a light spot on the recording surface of the optical disk And a photodetector used for focusing control, wherein the first and second regions are divided by the first reference line, and the third and fourth regions are divided by the second reference line. And the first and third regions are divided and the second and fourth regions are divided,
A first beam portion for projecting a reflected light beam traveling from the optical disc to the photodetector along a third direction onto the first and second regions along the first reference line; and the third and second A wavefront splitting optical element for splitting into a second beam portion that projects onto four regions;
Support for supporting the photodetector so that the position of the detection surface can be adjusted only in two axial directions perpendicular to each other in a plane parallel to the third direction and intersecting the first direction. Mechanism,
It is characterized by comprising.
[0009]
According to a third aspect of the present invention, in the optical head device of the optical disc player according to the first or second aspect, the two axial directions perpendicular to each other are the second and third directions.
[0010]
According to a fourth aspect of the present invention, in the optical head device of the optical disc player according to the third aspect, a plane including the second and third directions is perpendicular to the first direction.
[0011]
According to a fifth aspect of the present invention, in the optical head device of the optical disc player according to any one of the first to fourth aspects, the support mechanism holds the holder holding the photodetector and the holder. The support surface is defined by a plane parallel to the optical axis of the reflected light beam, and the holder is moved on the support surface to adjust the position of the detection surface. Is performed.
[0012]
According to a sixth aspect of the present invention, in the optical head device of the optical disc player according to the fifth aspect, the detection surface and the support surface are perpendicular to each other.
According to a seventh aspect of the present invention, there is provided an optical head device for an optical disc player according to the fifth or sixth aspect, which is used for tracking control for aligning the light spot and the track on the recording surface of the optical disc. And a separate support surface for supporting the separate photodetector, wherein the support surface and the separate support surface are parallel to each other.
[0013]
An eighth aspect of the present invention is an optical head device of an optical disc player,
A detection surface divided into first to fourth detection areas by first and second reference lines extending and intersecting in first and second directions perpendicular to each other, and forming a light spot on the recording surface of the optical disk And a photodetector used for focusing control, wherein the first and second regions are divided by the first reference line, and the third and fourth regions are divided by the second reference line. And the first and third regions are divided and the second and fourth regions are divided,
A first beam portion for projecting a reflected light beam traveling from the optical disc to the photodetector along a third direction onto the first and second regions along the first reference line; and the third and second A wavefront splitting optical element for splitting into a second beam portion that projects onto four regions;
And the distance between the first and second beam portions along the first reference line is set to about ½ of the length of the detection surface along the first reference line. Features.
[0014]
According to a ninth aspect of the present invention, in an optical head device of an optical disc player,
A detection surface divided into first to fourth detection areas by first and second reference lines extending and intersecting in first and second directions perpendicular to each other, and forming a light spot on the recording surface of the optical disk And a photodetector used for focusing control, wherein the first and second regions are divided by the first reference line, and the third and fourth regions are divided by the second reference line. And the first and third regions are divided and the second and fourth regions are divided,
A first beam portion for projecting a reflected light beam traveling from the optical disc to the photodetector along a third direction onto the first and second regions along the first reference line; and the third and second A wavefront splitting optical element for splitting into a second beam portion that projects onto four regions;
The angles formed by the first and second beam portions with respect to the third direction are θ1 and θ2, respectively, and the distance between the wavefront splitting optical element and the detection surface in the third direction is L In this case, L × tan (θ1−θ2) is set to about ½ of the length of the detection surface along the first reference line.
[0015]
According to a tenth aspect of the present invention, in the optical head device of the optical disc player according to the eighth or ninth aspect, the photodetector can adjust the position of the detection surface only in the second and third directions. It is fixed relative to the wavefront splitting optical element via a support mechanism.
[0016]
According to an eleventh aspect of the present invention, in the optical head device of the optical disc player according to the tenth aspect, a plane including the second and third directions is perpendicular to the first direction.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a plane of an optical head device according to an embodiment of the present invention and a signal processing unit of an optical disc player that has the optical head device and performs information reproduction and recording processing on an optical disc. It is a figure shown collectively. 2A is a vertical side view of the optical head device shown in FIG.
[0018]
This optical disk player includes a turntable (not shown) for rotating the optical disk, an optical head device 22 for irradiating the optical disk OD on the turntable with a laser beam and taking in a reflected laser beam from the optical disk OD. Have The turntable is driven by a spindle motor (not shown) supported by the base plate. The optical head device 22 includes a pickup, that is, a movable optical unit 24 that can move on a base plate, and a fixed optical unit 26 that is fixed to the base plate.
[0019]
More specifically, the pickup 24 is provided with a rising mirror 30 and an objective lens 32 as shown in FIG. The objective lens 32 forms an image of the laser beam from the fixed optical unit 26 on the recording surface of the optical disc and takes in the reflected laser beam reflected by the recording surface. The objective lens 32 is held by a lens holder 34, and the lens holder 34 is attached to an actuator 36. The actuator 36 is provided with a focusing coil and a tracking coil. With the focusing coil, the position of the objective lens 32 can be adjusted in the direction orthogonal to the recording surface of the optical disk, that is, in the optical axis direction of the objective lens 32. With the tracking coil, the position of the objective lens 32 can be adjusted in a direction crossing a track (groove) on the recording surface of the optical disk.
[0020]
The actuator 36 is mounted on a carriage 38, and the carriage 38 is slidably attached to a pair of guides 39. The guide 39 is extended along the radial direction on the turntable between the turntable for rotating the optical disc OD and the fixed optical unit 26. In addition, a pair of linear motors (not shown) are disposed with the guide 39 interposed therebetween, and the pickup 24 is driven along the guide 39 by the linear motor. Accordingly, the entire recording surface of the optical disk can be scanned by the objective lens 32 by the rotation of the optical disk OD and the linear movement of the pickup 24.
[0021]
The fixed optical unit 26 for sending the laser beam to the pickup 24 is provided with a laser beam light source 52, first and second photodetectors 54 and 56 for converting the reflected laser beam into an electrical signal, and the like. The The light source 52 of the fixed optical unit 26 is made of, for example, a semiconductor laser that has an elliptical beam cross-sectional shape and is divergent, and vibrates in one direction, that is, oscillates a linearly polarized laser beam. The laser beam oscillated from the light source 52 sequentially passes through the polarization beam splitter unit 58, the collimator lens 60, and the quarter wavelength plate 62, and is transmitted toward the pickup 24.
[0022]
The polarizing beam splitter unit 58 cooperates with the quarter wavelength plate 62 to separate the laser beam from the light source 52 toward the optical disk and the reflected laser beam from the optical disk. For example, if the linear polarization of the laser beam from the light source 52 is S-polarization and the linear polarization of the reflected laser beam from the optical disk is P-polarization, the polarization beam splitter unit 58 transmits the P-polarization component and the S-polarization component. Is set so as to have a characteristic of reflecting. In other words, the prism surface 58a of the polarization beam splitter unit 58 reflects the laser beam from the light source 52 and guides it toward the optical disc by changing the direction by 90 °, while transmitting the reflected laser beam from the optical disc.
[0023]
The quarter-wave plate 62 converts the linearly polarized laser beam into elliptically polarized light and the elliptically polarized laser beam into linearly polarized light. In other words, the S-polarized laser beam traveling from the polarization beam splitter unit 58 toward the optical disk becomes right-turning elliptically polarized light after passing through the quarter-wave plate 62. The right-turn elliptically polarized laser beam is reflected by the optical disk and returns as a left-turn reflected laser beam. The left-turn reflected laser beam becomes P-polarized light after passing through the quarter-wave plate 62. Accordingly, the polarization beam splitter unit 58 can separate the S-polarized laser beam from the light source 52 and the P-polarized reflected laser beam from the optical disk.
[0024]
The collimator lens 60 converts the divergent laser beam from the light source 52 into a parallel laser beam.
A half mirror 64 is disposed between the polarization beam splitter unit 58 and the first and second photodetectors 54 and 56. The reflected laser beam that has passed through the polarization beam splitter unit 58 is split by an approximately equal ratio by the half mirror 64 and sent to the first and second photodetectors 54 and 56.
[0025]
The first photodetector 54 is used for reproduction of information recorded on the recording surface of the optical disc and tracking control for aligning the light spot and the track on the recording surface. Tracking control is performed by adjusting the position of the objective lens 32 in a direction crossing the track on the recording surface of the optical disc via the tracking coil of the actuator 36.
[0026]
Further, a monitor light detector 66 for monitoring a change in the light intensity of the laser beam is disposed adjacent to the first light detector 54. The monitor light is obtained by reflecting a part of the laser beam from the light source 52 on the incident surface of the quarter-wave plate 62. The detection signal of the monitor light detector is used for auto power control (APC) for keeping the light intensity of the laser beam oscillated from the light source 52 constant.
[0027]
Between the half mirror 64 and the second photodetector 56, a hologram diffraction plate 68, which is a wavefront splitting optical element, is disposed in order to detect a focus error by a double knife edge method in a manner described later. That is, the second photodetector 56 is used for focusing control for forming an image of the light spot on the recording surface of the optical disc. Focusing control is performed by adjusting the position of the objective lens 32 in the optical axis direction via the focusing coil of the actuator 36.
[0028]
The signal processing unit 11 is provided with a power source for applying power to the entire optical disc player including the signal processing unit 11 and a CPU 12 as a main control device. A read only memory (ROM) 13 and a memory unit 14 are connected to the CPU 12. The ROM 13 stores initial data for operating the CPU 12. The memory unit 14 is a plurality of memories for temporarily storing information to be recorded supplied from the outside, data read from the optical disc, and data input via a host computer (not shown), etc. including.
[0029]
The CPU 12 is connected to a laser driving circuit 15, a recording laser beam generating circuit (laser modulation circuit) 16, and an APC circuit 17. The laser drive circuit 15 drives the light source 52 so as to generate a laser beam having a predetermined light intensity. The recording laser beam generating circuit 16 modulates the intensity of the laser beam emitted from the light source 52 according to the information to be recorded stored in the memory unit 14. The APC circuit 17 receives the detection signal from the monitor light detector 66 and controls the laser driving circuit 15 so as to maintain the light intensity of the laser beam oscillated from the light source 52 constant.
[0030]
Further, a tracking control circuit 18 and a focusing control circuit 19 are connected to the CPU 12. The tracking control circuit 18 determines the drive current to be supplied to the tracking coil of the actuator 36 based on the detection signal from the first photodetector 54, so that the objective lens in the direction crossing the track on the recording surface of the optical disc 32 movement amounts are controlled. The focusing control circuit 19 determines the amount of movement of the objective lens 32 in the optical axis direction by determining the drive current to be supplied to the focusing coil of the actuator 36 based on the detection signal from the second photodetector 56.
[0031]
3A is a front view showing a detection surface of the first photodetector 54, and FIG. 3B is a schematic diagram showing a flow of an electric signal supplied from the first photodetector 54 to the tracking control circuit 18. As shown in FIG. is there.
[0032]
As shown in FIG. 3A, the detection surface of the first photodetector 54 is divided into first and second detection regions 54a and 54b by a horizontal reference line TH. A reflected laser beam RB including a diffracted laser beam component by the groove G of the optical disk is projected onto the first and second detection areas 54a and 54b. The first and second detection regions 54a and 54b are configured by photodiodes, respectively. The first and second detection regions 54a and 54b convert the projected light beam into an electrical signal corresponding to the size of the light spot in each region.
[0033]
The detection electrical signals of the first and second detection regions 54a and 54b are taken out from the anodes of the photodiodes constituting these regions, and then amplified to a predetermined level by the amplifiers 72 and 74. Subsequently, the arithmetic unit 76 calculates the track deviation amount as “output of the amplifier 72 (first detection region 54 a) −output of the amplifier 74 (second detection region 54 b)”, and supplies it to the tracking control circuit 18. .
[0034]
Further, the outputs of the cathodes of the photodiodes constituting the first and second detection regions 54 a and 54 b are added by another operational amplifier 78. This added value is supplied to the CPU 12 and the memory unit 14 as information recorded in the pits of the optical disk.
[0035]
FIG. 4A is a front view showing the relationship between the hologram pattern of the wavefront splitting optical element, that is, the hologram diffraction plate 68, and the reflected laser beam. FIG. 4B is a front view showing the light receiving surface of the second photodetector 56, and FIG. 4C is a schematic diagram showing the flow of electrical signals supplied from the second photodetector 56 to the focusing control circuit 19. is there.
[0036]
As shown in FIG. 4B, the light receiving surface of the second photodetector 56 has an intersection of center lines O1 and O2 orthogonal to each other at the optical axis of the reflected laser beam in the optical disk device 22 (that is, on the hologram diffraction plate 68). The optical axis of the incident reflected laser beam is set to penetrate perpendicularly. An upper detection surface A1 having first to fourth detection regions 56a to 56d divided by a vertical reference line FV and a horizontal reference line FH is disposed above the light receiving surface of the second photodetector 56. The first to fourth detection regions 56a to 56d are each configured by a photodiode. The first to fourth detection areas 56a to 56d convert the projected light beam into an electrical signal corresponding to the size of the light spot in each area.
[0037]
It should be noted that four regions 56e equivalent to these regions are also formed below the light receiving surface of the second photodetector 56, with the first to fourth detection regions 56a to 56d of the upper detection surface A1 centered on the center line O2. A lower detection surface A2 consisting of ˜56h can be provided.
[0038]
As shown in FIG. 4C, the detection electric signals of the first to fourth detection regions 56a to 56d are taken out from the anodes of the photodiodes constituting these regions, and then amplified to a predetermined level by the amplifiers 81 to 84. Is done. Subsequently, the calculator 85 adds the signals of the first and third detection areas 56a and 56c, and the calculator 86 adds the signals of the second and fourth detection areas 56b and 56d. Further, the computing unit 87 determines that “the output of the computing unit 85 (first and third detection areas 56a, 56c) −the output of the computing unit 86 (second and fourth detection areas 56b, 56d)” is the amount of defocus. It is calculated and supplied to the focusing control circuit 19.
[0039]
As shown in FIG. 4A, the hologram pattern of the hologram diffraction plate 68 includes first to fourth pattern portions 68a to 68d. The first and second pattern portions 68a and 68b are formed so that beam portions BP1 and BP2 having the same width from the center of the reflected laser beam RB pass through. The third and fourth pattern portions 68c and 68d are formed so that the left and right outer portions of the reflected laser beam RB outside the beam portions BP1 and BP2 pass through.
[0040]
The first pattern portion 68a has a narrow pitch so that the + 1st order diffracted light of the beam portion BP1 is directed to the first and second detection regions 56a and 56b of the upper detection surface A1 of the second photodetector 56. The second pattern portion 68b has a wide pitch so that the + 1st order diffracted light of the beam portion BP2 is directed to the third and fourth detection regions 56c and 56d of the upper detection surface A1 of the second photodetector 56.
[0041]
The third and fourth pattern portions 68c and 68d are set such that ± 1st order diffracted light of the left and right outer portions of the reflected laser beam RB deviates from the upper and lower detection surfaces A1 and A2 of the second photodetector 56. Has a pitch. That is, the third and fourth pattern portions 68c and 68d are diffraction pattern portions for preventing the left and right outer portions of the reflected laser beam RB from being used as information for focusing control. In this way, the sensitivity of focusing control can be set to an appropriate level.
[0042]
The position on the light receiving surface of the second photodetector 56 toward which the −1st order diffracted light beams of the beam portions BP1 and BP2 by the first and second pattern portions 68a and 68b are directed is the light reception of the second photodetector 56 described above. This corresponds to the lower detection surface A2 including the four regions 56e to 56h that can be disposed at the lower portion of the surface. A zero-order light component of the reflected laser beam is imaged at the intersection of the center lines O1 and O2 of the light receiving surface of the second photodetector 56.
[0043]
When the light spot is focused on the recording surface of the optical disc, the beam portion BP1 that has passed through the first pattern portion 68a having a narrow pitch is on the vertical reference line FV between the first and second detection regions 56a and 56b. Projected as a spot. At this time, similarly, the beam portion BP2 that has passed through the second pattern portion 68b having a wide pitch is projected as a spot on the vertical reference line FV between the third and fourth detection regions 56c and 56d. Therefore, “the output of the calculator 85 (first and third detection areas 56a and 56c) −the output of the calculator 86 (second and fourth detection areas 56b and 56d)” in the calculator 87 becomes substantially zero. , You can see that it is in focus.
[0044]
However, for example, when the light spot is focused in front of the recording surface of the optical disc, the beam portions BP1 and BP2 that have passed through the first and second pattern portions 68a as shown in FIG. And it is projected in the shape of a half moon in the third detection areas 56a and 56c. Therefore, “the output of the calculator 85 (first and third detection areas 56a and 56c) −the output of the calculator 86 (second and fourth detection areas 56b and 56d)” in the calculator 87 is a certain positive value. Thus, it can be seen that the focus is shifted forward.
[0045]
Conversely, when the light spot is focused behind the recording surface of the optical disc, the beam portions BP1 and BP2 that have passed through the first and second pattern portions 68a are in the second and fourth detection regions 56b and 56d, respectively. Projected in a half moon shape. Therefore, “the output of the calculator 85 (first and third detection areas 56a and 56c) −the output of the calculator 86 (second and fourth detection areas 56b and 56d)” in the calculator 87 is negative. Value, and it can be seen that the focus is shifted to the back.
[0046]
Next, the positional relationship between the first and second photodetectors 54 and 56 and the hologram diffraction plate 68 will be described.
The fixed optical unit 26 of the optical head device 22 is surrounded by a rectangular casing 42. The casing 42 includes a hard casing main body 43 and a hard circuit board 44 attached as a top plate to the casing main body 43 by a fixing screw 45. The circuit board 44 is placed on the support surface 43 a at the upper end of the casing body 43. The support surface 43a is arranged in a horizontal plane so as to be parallel to a plane including the optical axis of the optical system in the fixed optical unit 26 (the optical axis of the laser beam from the light source 52 and the optical axis of the reflected laser beam from the optical disk). It is prescribed. The circuit board 44 has a substantially uniform thickness. Therefore, the upper surface of the circuit board 44 is also horizontal.
[0047]
The first photodetector 54 and the monitor photodetector 66 are attached to the upper surface of the circuit board 44 so that their detection surfaces are horizontal and face down. The first photodetector 54 can be positioned with respect to the reflected laser beam reflected by the half mirror 64 by adjusting the fixed position of the circuit board 44 with respect to the casing body 43. More specifically, since the hole formed for passing the fixing screw 45 is larger than the screw 45, the position is adjusted by sliding the circuit board 44 on the support surface 43a with the screw 45 loosened. can do.
[0048]
On the other hand, the second photodetector 56 is fixed to the vertical portion 46a of the holder 46 having the vertical portion 46a and the horizontal portion 46b. The detection surface of the second photodetector 56 is set to be perpendicular to the optical axis of the reflected laser beam in the fixed optical unit 26. The holder 46 is placed on the support surface 43 b at the upper end of the casing body 43 through the horizontal portion 46 b and is attached by a fixing screw 47. The second photodetector 56 and the circuit board 44 are connected in circuit by a flexible circuit board 48.
[0049]
The support surface 43b is defined by a horizontal plane in the same manner as the support surface 43a. The second photodetector 55 can be positioned with respect to the reflected laser beam transmitted through the half mirror 64 by adjusting the fixing position of the holder 46 with respect to the casing body 43. More specifically, since the hole formed in the holder 46 for passing the fixing screw 47 is larger than the screw 47, the position of the holder 46 can be determined by sliding the holder 46 on the support surface 43b with the screw 47 loosened. Can be adjusted.
[0050]
That is, the first and second photodetectors 54 and 56 are both optical axes of the optical system in the fixed optical unit 26 (the optical axis of the laser beam from the light source 52 and the optical axis of the reflected laser beam from the optical disk). Can be adjusted in two axial directions perpendicular to each other in a plane parallel to the plane including the same (in the present embodiment, the same horizontal plane). Here, the biaxial direction is composed of a Z direction parallel to the optical axis of the reflected laser beam in the fixed optical unit 26 and one X direction in a plane perpendicular to the optical axis. With such a configuration, the position adjustment of the first and second photodetectors 54 and 56 can be performed by accessing from the same direction (upper side in the present embodiment), and workability is improved.
[0051]
The first photodetector (track PD) 54 and the monitor photodetector 66 for performing tracking control in addition to the above-described two axis directions of Z and X further adjust the position in the third axis direction, that is, the Y direction. Therefore, a known structure such as an adjusting screw member is incorporated. Further, the second photodetector (focus PD) 56 for performing the focusing control is set so as to satisfy the following conditions in order to eliminate the adverse effects caused by the position adjustment only in the biaxial direction.
[0052]
That is, as shown in FIG. 2B, in the second photodetector 56, the distance d1 between the two beam portions BP1 and BP2 along the vertical reference line FV of the upper detection surface A1 is the vertical reference line FV. It is set to about ½ of the length D of the upper detection surface A1 along. In other words, the angles formed by the beam portions BP1 and BP2 with respect to the Z direction parallel to the optical axis of the reflected light beam incident on the hologram diffraction plate 68 are θ1 and θ2, respectively. When the distance from the upper detection surface A1 of the photodetector 56 is L, the value obtained by L × tan (θ1−θ2) is the length D of the upper detection surface A1 along the vertical reference line FV. It is set to about 1/2.
[0053]
Further, D / 2 is set to be sufficiently larger than a value obtained by adding the mounting tolerance of the second photodetector 56 and the optical axis tolerance.
By performing such a condition setting, the margin for the positional deviation of the second photodetector (focus PD) 56 in the Y direction is increased, and the adverse effect caused by the position adjustment only in the two axis directions of the Z and X directions is substantially eliminated. Disappear. Accordingly, the second light detector 56 can be sufficiently positioned and set only in the two-axis directions, the position adjustment work time can be shortened, and the second light can be detected even if conditions such as temperature change after the position adjustment. The detector 56 is less likely to be displaced.
[0054]
In the illustrated embodiment, a hologram diffraction plate 68 is used as the wavefront splitting optical element. However, the reflected laser beam is applied to the first beam portion corresponding to the first and second regions 56a and 56b and the third and fourth regions 56c and 56d along the vertical reference line FV of the second photodetector 56. The function of dividing into the corresponding second beam portion can also be obtained by other various optical elements such as a combination of two prisms or a combination of two parallel flat glass plates. That is, the concept of a wavefront splitting optical element includes all optical elements that perform such a function.
[0055]
While the present invention has been described with reference to the embodiments shown in the accompanying drawings, the present invention can be implemented in various modes other than the illustrated embodiments within the scope of the idea.
[0056]
【The invention's effect】
According to the present invention, since the position of the focus PD (photodetector for performing focusing control) is adjusted only in the biaxial direction, the work time required for position adjustment is shortened, and the position of the focus PD after position adjustment is reduced. Misalignment is less likely to occur.
[0057]
In addition, since the focus PD and the track PD (photodetector for performing tracking control) can be accessed from the same direction to adjust the position, workability is improved.
[0058]
Further, by setting the position and size of the detection surface of the focus PD with respect to the distance between the first and second beam portions obtained by the wavefront splitting optical element, the focus in the remaining one-axis direction without position adjustment is set. The margin for the positional deviation of the PD is increased, and the adverse effects due to the position adjustment only in the biaxial direction are substantially eliminated.
Therefore, according to the present invention, it is possible to provide an optical head device of an optical disc player having good operability and high reliability.
[Brief description of the drawings]
FIG. 1 shows a plane of an optical head device according to an embodiment of the present invention and a signal processing unit of an optical disk player that has the optical head device and performs information reproduction and recording processing on an optical disk. FIG.
2A is a longitudinal side view of the optical head device shown in FIG. 1, and FIG. 2B is an enlarged view showing a relationship between a second photodetector and a hologram diffraction plate.
3A is a front view showing a detection surface of a first photodetector, and FIG. 3B is a schematic diagram showing a flow of an electric signal supplied from the first photodetector to a tracking control circuit.
4A is a front view showing the relationship between the hologram pattern of the hologram diffraction plate and the reflected laser beam, FIG. 4B is a front view showing the light receiving surface of the second photodetector, and FIG. 4C is the second light. Schematic which shows the flow of the electric signal supplied to a focusing control circuit from a detector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Signal processing part, 22 ... Optical head apparatus, 24 ... Pickup (movable optical part), 26 ... Fixed optical part, 30 ... Rising mirror, 32 ... Objective lens, 39 ... Guide, 42 ... Casing, 43 ... Casing main body 44 ... Circuit board 45 ... Fixing screw 46 ... Holder 47 ... Fixing screw 48 ... Flexible circuit board 52 ... Light source 54 ... First photodetector 56 ... Second photodetector 58 ... Polarized beam Splitter unit, 60 ... collimator lens, 62 ... 1/4 wavelength plate, 64 ... half mirror, 66 ... monitor photodetector, 68 ... hologram diffraction plate (wavefront dividing optical element).

Claims (6)

A detection surface divided into first to fourth detection areas by first and second reference lines extending and intersecting in first and second directions perpendicular to each other, and forming a light spot on the recording surface of the optical disk And a photodetector used for focusing control, wherein the first and second regions are divided by the first reference line, and the third and fourth regions are divided by the second reference line. And the first and third regions are divided and the second and fourth regions are divided,
A reflected light beam traveling from the optical disc to the photodetector along a third direction intersecting the first and second directions is projected onto the first and second regions along the first reference line. A wavefront splitting optical element for splitting into one beam part and a second beam part projected onto the third and fourth regions;
A support mechanism for fixing the photodetector relative to the wavefront splitting optical element and allowing the position of the detection surface to be adjusted in the second and third directions;
And the distance between the first and second beam portions along the first reference line extending in the first direction is about ½ of the length of the detection surface along the first reference line. An optical head device for an optical disc player, characterized in that A detection surface divided into first to fourth detection areas by first and second reference lines extending and intersecting in first and second directions perpendicular to each other, and forming a light spot on the recording surface of the optical disk And a photodetector used for focusing control, wherein the first and second regions are divided by the first reference line, and the third and fourth regions are divided by the second reference line. And the first and third regions are divided and the second and fourth regions are divided,
A reflected light beam traveling from the optical disc to the photodetector along a third direction intersecting the first and second directions is projected onto the first and second regions along the first reference line. A wavefront splitting optical element for splitting into one beam part and a second beam part projected onto the third and fourth regions;
A support mechanism for fixing the photodetector relative to the wavefront splitting optical element and allowing the position of the detection surface to be adjusted in the second and third directions;
The angles formed by the first and second beam portions with respect to the third direction are θ1 and θ2, respectively, and the distance between the wavefront splitting optical element and the detection surface in the third direction is L L × tan (θ1−θ2) is set to about ½ of the length of the detection surface along the first reference line extending in the first direction. Head device. The support mechanism, the optical head apparatus for an optical disc player according to claim 1 or 2, characterized that you allow to adjust the position of the detection surface only in the second and third directions. According to any one of claims 1 to 3, wherein the second and third directions are perpendicular to each other and a plane including said second and third direction is perpendicular to the first direction An optical head device of an optical disc player. The support mechanism includes a holder for holding the photodetector and a support having a support surface for mounting the holder, and the support surface is formed by a plane parallel to the optical axis of the reflected light beam. 5. The optical head device of the optical disk player according to claim 3, wherein the position of the detection surface is adjusted by being defined and moving the holder on the support surface. And further comprising another photodetector used for tracking control for aligning the light spot and track on the recording surface of the optical disc, and another support surface for supporting the other photodetector. 6. The optical head device of an optical disc player according to claim 5 , wherein the support surface and the another support surface are parallel to each other.

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