JP3471501B2 - Optical head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for reading / writing data from / to an optical disk by using a light spot which is made by making a laser beam incident on an objective lens and condensing on the optical disk.

[0002]

2. Description of the Related Art FIG. 17 is a diagram for explaining the structure of a conventional optical head. In FIG. 17, 2 is a beam splitter, 4 is a polarization beam splitter, and 9
Is a half-wave plate made of crystal material such as quartz.
Is a light receiving element A, and 20 is a light receiving element B. Reference numeral 10 is a laser light source, which is a linearly polarized laser beam 11
Is arranged so that the plane of polarization is P-polarized light having an oscillation axis parallel to the plane of incidence of the beam splitter 2. The beam splitter 2 transmits a part of P-polarized light (linearly polarized light having an oscillation axis parallel to the incident surface of the beam splitter) and S-polarized light (linearly polarized light having an oscillation axis perpendicular to the incident surface of the beam splitter)
Totally reflects. Since the laser beam 11 incident on the beam splitter 2 is P-polarized light, part of it is transmitted as it is. Reference numeral 12 is an objective lens, which transmits a laser beam 11 transmitted through the beam splitter 2 to a light spot 13
Focus on. The light spot 13 is positioned on the information track on the optical disc by moving the objective lens 12 in the focus direction 14 and the tracking direction 15.

When the laser beam 11 is reflected by the information track on the optical disk, it becomes reflected light whose oscillation axis is rotated by .theta.K by the information pit recorded magneto-optically.
The reflected light is incident on the beam splitter 2 via the objective lens 12. A part of the reflected light incident on the beam splitter 2 becomes the optical axis 16a and is guided to the ½ wavelength plate 9. The half-wave plate 9 rotates the oscillation axis of the optical axis 16 which is linearly polarized light by 45 degrees to form the optical axis 16b and makes it enter the polarization beam splitter 4. The polarization beam splitter 4 is P
Only polarized light is transmitted and S polarized light is reflected. Since the main oscillation axis of the optical axis 16b is rotated 45 degrees with respect to the incident surface of the polarization beam splitter 4 by the ½ wavelength plate 9, the light quantity of the optical axis 16b is equally divided, and half of the light axis is transmitted. It becomes 17 and is irradiated to the light receiving element A, and half of the light is reflected to become the optical axis 18 and is irradiated to the light receiving element b.

At this time, from the light source 10 to the beam splitter 2
The optical path length from the beam splitter 2 to the light receiving element A19 is longer than the optical path length up to the light receiving element A19.
Is placed. Also, from the light source 10 to the beam splitter 2
The optical path length from the beam splitter 2 to the light receiving element B20 is shorter than the optical path length up to the light receiving element B20.
Is placed.

The light receiving area of the light receiving element A19 is 19a, 19a.
It is divided into three areas, c and 19b. Optical axis 17
The center of is located on 19c. The light receiving area of the light receiving element B20 is divided into three areas 19a, 19b, and 19c + 19d in the direction corresponding to the direction of the information track on the optical disc. Further, 19c + 19d is divided into two areas 19c and 19d in the tracking direction 15 which is a direction crossing the information track on the optical disc. The center of the optical axis 18 is located on the boundary between 19c and 19d. Reference numeral 21 denotes a differential amplifier, which generates a difference signal 22 between the detection output (19a + 19b) on the light receiving element A19 and the detection output (20a + 20b) on the light receiving element B20. 23
Is a differential amplifier, and generates a difference signal 24 between the detection output 19c in the central portion on the light receiving element A19 and the detection output (20c + 20d) in the central portion on the light receiving element B20. Reference numeral 25 denotes a differential amplifier, which is a detection output 20 divided in a direction crossing an information track on the optical disc on the light receiving element B20.
Generate a difference signal 26 of c and 20d.

Next, the operation of the above conventional example will be described.
As shown in FIG. 17, the laser beam 11 emitted from the laser light source 10 is focused on the information track on the optical disc by the objective lens 12. The reflected light of the laser beam 11 reflected on the information track is incident on the beam splitter 2 via the objective lens 12 again. The reflected light is received by the beam splitter 2, the half-wave plate 9 and the polarization beam splitter 4 in the light receiving element A1.
9 and the light receiving element B20.

In FIG. 17, the position of the light receiving element A19 is adjusted so that the optical path length from the beam splitter 2 to the light receiving element A19 is longer than the optical path length from the light source 10 to the beam splitter 2. Further, since the position of the light receiving element B20 is adjusted so that the optical path length from the beam splitter 2 to the light receiving element B20 is shorter than the optical path length from the light source 10 to the beam splitter 2, the light spot 13 becomes If the laser light source 10 side in the focus direction 14 is deviated from the information track, the light receiving element A1
The light spot 17 on 9 becomes small, and the ratio of irradiation to the light receiving region 19c becomes large, so that the detection output of 19c becomes large. Further, the light spot 18 on the light receiving element B19 becomes large, and the ratio of irradiation to the light receiving region (20c + 20d) becomes small, so that the detection output of (20c + 20d) becomes small. Therefore, the differential signal 24 becomes large. On the contrary, when the light spot 13 is deviated to the disc side in the focus direction 14 with respect to the information track, the differential signal 24 becomes small. Therefore, if the light spot 13 is moved in the focus direction 14 so that the differential signal 24 has a predetermined value, the light spot 13 can be focused on the information track.

In FIG. 17, the tracking direction is 15
Therefore, the laser beam reflected by the information track contains the first-order diffracted light that is diffracted in the 15 directions by the information track. The tracking operation can be performed by utilizing the fact that the intensity of the first-order diffracted light changes in the tracking direction due to the change in the relative position of the information track and the light spot 13 in the tracking direction. Here, the light receiving element B
20 is 20c and 20 with respect to the tracking direction 15.
Since the light spot 13 is divided into d, if the light spot 13 is moved in the tracking direction 15 so that the differential signal 26 of 20c and 20d becomes a predetermined value, the light spot 13 can perform a tracking operation on the information track. .

Here, in order to perform the focusing operation, in FIG. 17, the optical path length from the beam splitter 2 to the light receiving element A19 is longer than the optical path length from the light source 10 to the beam splitter 2. Light receiving element A
The position of 19 is adjusted, and the position of the light receiving element B20 is adjusted so that the optical path length from the beam splitter 2 to the light receiving element B20 is shorter than the optical path length from the light source 10 to the beam splitter 2. It is necessary to position the center of the light spot 17 on the light receiving element A19 in the light receiving area 19c and the center of the light spot 18 on the light receiving element B20 in the light receiving area 20c + 20d. Further, in order to perform the tracking operation, in FIG.
It is necessary to position the center of the light spot 18 on the light receiving element B20 in the X direction at the boundary between the light receiving regions 20c and 20d. In the conventional optical head, two light receiving elements A1
9 and B20 are individually positioned and adjusted with respect to the respective optical axes 17 and 18.

In FIG. 17, the optical axis 16a, which is the reflected light from the optical disc, contains the information recorded in the information track on the optical disc as the rotation of the polarization plane ± θk, and at the same time, the intensity of the emitted light of the laser light source itself. It also includes light intensity fluctuations due to fluctuations and reflectance fluctuations on the optical disk.
The polarization beam splitter 4 transmits only P-polarized light and reflects S-polarized light. Since the main oscillation axis of the optical axis 16b is rotated by 45 ° with respect to the incident surface of the polarization beam splitter 4 by the half-wave plate 9, the optical axis 17 that has passed through the polarization beam splitter 4 and the optical axis 18 that has reflected it The DC component due to the light intensity fluctuation is equal, and the signal component due to the polarization plane rotation ± θk has an opposite phase. The transmitted light 17 is applied to the light receiving element A19, and the reflected light 18 is applied to the light receiving element B20.
Therefore, the detection output (19a + 19) on the light receiving element A19
b) and the detection output on the light receiving element B20 (20a + 20b)
It is possible to reproduce the signal magneto-optically recorded on the information track on the optical disc from the difference signal 22 from

Here, in the above-mentioned conventional optical head, 1 / is provided between the beam splitter 2 and the polarization beam splitter 4.
Since the two wavelength plate is installed, the optical path length from the beam splitter 2 to the light receiving element B20 becomes long, and therefore the laser light source 1 which must be longer than the optical path length.
The optical path length from 0 to the beam splitter 2 and the optical path length from the beam splitter 2 to the light receiving element A19 are further increased, and at the same time, since the output light from the laser light source is divergent light, the optical path length from the laser light source to the beam splitter is increased. As a result, the diameter of the laser beam is increased, the sizes of the beam splitter, the half-wave plate, and the polarization beam splitter are increased, and as a result, the size of the optical head is increased. Also, in order to individually position the optical components that guide the laser beam (beam splitter, half-wave plate, polarization beam splitter), it is necessary to have a space for individually installing positioning reference pins, fixing brackets, etc. The size of the optical head increases. As described above, the conventional optical head can also perform the focusing operation and the tracking operation to reproduce the magneto-optical signal on the optical disk.

[0012]

However, in the above-described conventional optical head, since the half-wave plate is installed between the beam splitter and the polarization beam splitter, the optical path length from the beam splitter to one light receiving element is increased. , Therefore, the optical path length from the laser light source to the beam splitter and the optical path length from the beam splitter to the other light receiving element, which must be longer than the optical path length, are further lengthened, and at the same time, the output light from the laser light source is Since it is divergent light, the optical parts (beam splitter, half-wave plate, and polarization beam splitter) are installed at the position where the diameter of the laser beam becomes large due to the long optical path from the laser light source to the beam splitter. Therefore, the size of each optical component increases, and as a result, the size of the optical head increases. There is a problem in that.

Further, optical parts (beam splitter, 1 /
There is a problem in that the size of the optical head becomes large because a space for separately setting the positioning reference pins, fixing brackets, etc. is required to individually position the two-wavelength plate and the polarization beam splitter.

Further, the above-mentioned conventional optical head has a problem that the number of assembly adjustment steps is large because the positions of the two light receiving elements must be adjusted individually.

Further, in the above-mentioned conventional optical head, the polarization plane of the optical axis incident on the polarization beam splitter is halved in order to equally divide the amount of light to the two light receiving elements for differentially detecting the magneto-optical signal. Since it is necessary to rotate by 45 degrees using the wave plate, there is a problem that a 1/2 wave plate made of an expensive crystal material must be used.

The present invention has been made in view of the above conventional problems, and a first object thereof is to provide a compact optical head.

A second object of the present invention is to provide an inexpensive optical head by reducing the number of assembly and adjustment steps.

A third object of the present invention is to provide an inexpensive optical head capable of detecting a magneto-optical signal without using an expensive crystal material.

A fourth object of the present invention is to solve the above problems and to provide a compact optical head having a compact structure and capable of tracking three beams.

A fifth object of the present invention is to provide an optical head which solves the above-mentioned problems and at the same time does not cause the deviation of the optical axis due to the fluctuation of the laser wavelength caused by the fluctuation of temperature and the fluctuation of laser output power. is there.

A sixth object of the present invention is to solve the above-mentioned problems and at the same time to provide a compact optical head having a compact structure and capable of controlling the laser output constantly.

[0022]

In order to achieve the above object, the present invention provides a single optical component for guiding a laser beam.
By integrating with the compound prism, the optical component (μ compound prism) can be attached to the position where the diameter of the laser beam is small near the laser light source.

Further, in order to achieve the above object, the present invention provides a μ compound prism in which optical components for guiding a laser beam are integrated, and a surface A which is an optical component for guiding reflected light from a disk to a signal detection system. (Beam splitter or
Half mirror), a surface B (total reflection surface) parallel to the surface A, and a surface parallel to the bottom surface of the μ compound prism between the surface A and the surface B. The surface A with the axis perpendicular to the line of intersection of A and the bottom surface as the center of rotation
Provide a surface C that is a surface rotated by 45 degrees on a surface parallel to
The reflected light from the disk is split into an optical axis A that passes through the surface C and goes straight, and an optical axis B that is reflected by the surface C.
Also, one of the light receiving elements A having two optical axes A is
The optical axis B is reflected on the surface B and then the other light receiving element B is irradiated. Further, a direction parallel to the bottom surface of the μ compound prism and perpendicular to a line of intersection of the surface A and the low surface is defined as a major axis direction, and a direction parallel to the bottom surface and perpendicular to the major axis direction is a minor axis direction of the μ compound prism. In this case, the light receiving element A is divided only in the major axis direction of the μ compound prism, and the light receiving element B is divided in the major axis direction and the minor axis direction of the μ compound prism.

Further, in order to achieve the above object, according to the present invention, instead of rotating the polarization plane of the optical axis incident on the polarization beam splitter by 45 degrees, the polarization beam splitter itself is rotated by 45 degrees with respect to the optical axis. I have to.

Further, in order to achieve the above object, the present invention is provided with a three-beam grating pattern integrally on the surface of the μ compound prism on which the laser beam is emitted from the laser light source.

Further, in order to achieve the above object, the present invention can be realized by an optical system for guiding a laser beam from a laser light source to a disk and an optical system for guiding a reflected light from the disk to a light receiving element, each having a reflecting surface and a straight transmitting surface. Therefore, the directions of all the optical axes are geometrically determined, and there is no place where the direction of the optical axis is determined by refraction.

In order to achieve the above-mentioned object, the present invention sets the major axis direction to be parallel to the bottom surface of the μ compound prism and perpendicular to the line of intersection of the surface A and the lower surface, and is parallel to the bottom surface to define the major axis direction. When the direction perpendicular to is the minor axis direction of the μ compound prism,
The reflection surface having an angle of 40 to 50 degrees with the lower surface including the minor axis direction is provided on the side where the surface A forms an angle of 45 degrees with the bottom surface.

Therefore, according to the present invention, the optical component (μ compound prism) can be attached to the position where the diameter of the laser beam is small in the vicinity of the laser light source by the above means, so that the size of the optical component can be reduced. Therefore, a small optical head can be provided.

Further, according to the present invention, by the above means, the light irradiated on the light receiving element B is maintained while the positional relationship between the position of the laser light source and the position of the optical axis A irradiated on the light receiving element A is kept constant. Since the position of axis B can be adjusted by moving the entire μ compound prism, only the μ compound prism can be installed on the low-precision assembled light emitting / receiving module (laser light source and assembly of two light receiving elements). Since it is only necessary to adjust the position, it is possible to provide an inexpensive optical head by reducing the number of assembly and adjustment steps.

According to the present invention, the polarization beam splitter itself is rotated by 45 degrees with respect to the optical axis by the above means, instead of rotating the polarization plane of the optical axis incident on the polarization beam splitter by 45 degrees. It is possible to provide an inexpensive optical head capable of detecting a magneto-optical signal without using a half-wave plate made of an expensive crystal material.

Further, according to the present invention, since the three-beam grating pattern is integrally provided on the surface on which the laser beam is incident from the laser light source of the μ compound prism by the above means, the three-beam grating has a compact structure. It is possible to provide a small optical head capable of tracking.

Further, according to the present invention, by the above means, the optical system for guiding the laser beam from the laser light source to the disk and the optical system for guiding the reflected light from the disk to the light receiving element are all composed of a reflecting surface and a straight transmitting surface. Since the direction of the optical axis is geometrically determined and there is no part that determines the direction of the optical axis by refraction, the optical axis of the optical axis due to fluctuations in the laser wavelength caused by temperature fluctuations and laser output power fluctuations It is possible to provide an optical head that does not cause displacement.

Furthermore, according to the present invention, a part of the laser beam emitted from the laser light source reflected by the surface A which is the half mirror or the beam splitter of the μ compound prism is utilized as the output monitor beam of the laser light source by the above means. Thus, it is possible to provide a compact optical head that has a compact configuration and can control the laser output constantly.
Further, since the light receiving element for receiving the output monitoring beam can be integrated with the light emitting / receiving module, it is possible to provide a compact optical head having a compact configuration and capable of controlling the laser output at a constant level.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is a μ compound prism having a bottom surface and an upper surface which are parallel to each other, and a surface A having an inclination of 45 degrees with respect to the bottom surface.
The surface A is disposed on the side opened at an angle of 135 degrees with respect to the bottom surface, and the surface B is parallel to the surface A. The plane parallel to
Face C, which is the face rotated at an angle smaller than 90 degrees , is face A.
And a surface B, a μ compound prism, a laser light source, two or more light receiving elements, and an objective lens are provided, and the laser beam emitted from the laser light source is passed through the μ compound prism to the objective. An optical head for reading / writing data from / to an optical disk by using a light spot which is incident on a lens and condensed on the optical disk, and an optical axis A which allows reflected light from the disk to pass through a surface C and go straight. And the optical axis B reflected by the surface C, and
The optical axis A is irradiated onto one of the two light receiving elements, and the optical axis B is reflected on the surface B and then irradiated onto the other light receiving element B.

According to a second aspect of the present invention, there is provided a μ compound prism having a bottom surface and a top surface which are parallel to each other.
A surface A having an inclination of 45 degrees with respect to the bottom surface, a surface B arranged on the side opened at an angle of 135 degrees with respect to the bottom surface and parallel to the surface A, and a surface A parallel to the bottom surface. A plane parallel to the plane A is rotated by 90 degrees with the axis perpendicular to the line of intersection with the bottom as the center of rotation.
The surface C, which is a surface rotated at a small angle, is provided between the surfaces A and B, and the surface D, which is at least a part of the side surface where the distance between the surfaces A and C is large, is relative to the bottom surface. Over 90 degrees 135
A μ-composite prism that forms an angle of less than or equal to a degree, a laser light source, two or more light-receiving elements, and an objective lens are provided, and a laser beam emitted from the laser light source passes through the μ-complex prism. Then, an optical head for reading / writing data from / to the optical disk is formed by using a light spot which is incident on the objective lens and condensed on the optical disk.

The invention according to claim 3 of the present invention is a μ compound prism having a bottom surface and an upper surface which are parallel to each other,
A surface A having an inclination of 45 degrees with respect to the bottom surface, a surface B arranged on the side opened at an angle of 135 degrees with respect to the bottom surface and parallel to the surface A, and a surface A parallel to the bottom surface. A plane parallel to the plane A is rotated by 90 degrees with the axis perpendicular to the line of intersection with the bottom as the center of rotation.
The surface C, which is a surface rotated at a small angle, is provided between the surfaces A and B, and the surface D, which is at least a part of the side surface where the distance between the surfaces A and C is large, is relative to the bottom surface. Over 45 degrees, 9
The μ compound prism is provided with a μ compound prism characterized by forming an angle of less than 0 °, a laser light source, two or more light receiving elements, and an objective lens, and the laser beam emitted from the laser light source is the μ compound prism. An optical head for reading / writing data from / to the optical disc by using a light spot which is incident on the objective lens via the and condensed on the optical disc.

The invention according to claim 4 of the present invention is the invention according to any one of claims 1 to 3, wherein the surface A of the μ compound prism is a half mirror and the surface B is a total reflection surface. The surface C is configured by a half mirror to provide an optical head.

According to a fifth aspect of the present invention, in any one of the first to third aspects of the invention, the surface C of the μ compound prism is parallel to the bottom surface of the μ compound prism and the surface A and the bottom surface intersect. With the axis perpendicular to the line as the center of rotation, the plane parallel to plane A is 45
A surface rotated by a degree, the surface A is composed of a half mirror or a polarization beam splitter, the surface B is composed of a total reflection surface, and the surface C is composed of a polarization beam splitter, whereby a magneto-optical signal can be reproduced. The optical head is characterized by the above.

According to a sixth aspect of the present invention, in any one of the first to third aspects of the present invention, a diffraction grating is integrally formed on the surface of the μ compound prism on which the laser beam is incident from the laser light source. The optical head is characterized by enabling three-beam tracking.

According to a seventh aspect of the present invention, in any one of the first to third aspects of the invention, the direction parallel to the bottom surface of the μ compound prism and perpendicular to the line of intersection of the surface A and the low surface is long. When the axial direction is parallel to the bottom surface and the direction perpendicular to the long axis direction is the short axis direction of the μ compound prism, the reflection surface having the angle of 40 to 50 degrees with the low surface including the short axis direction is a surface A. The optical head is characterized in that the laser output can be controlled to a constant value by being provided on the side that makes an angle of 45 degrees with the bottom surface.

According to an eighth aspect of the present invention, in any one of the first to third aspects of the present invention, the direction parallel to the bottom surface of the μ compound prism and perpendicular to the line of intersection of the surface A and the low surface is long. When the axial direction is parallel to the bottom surface and the direction perpendicular to the major axis direction is the minor axis direction of the μ compound prism, the reflection of the light receiving elements A and C arranged to receive the reflected light of the surface B A light receiving element B arranged so as to receive light or the reflected light of the surface C whose direction is changed by the surface D.
Is divided only in the long axis direction of the μ compound prism, and the light receiving element B is divided in the long axis direction and the short axis direction of the μ compound prism.

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

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the structure of a μ compound prism used in this embodiment. The μ composite prism 201 has bottom surfaces MN parallel to each other.
GH and top ABOP, 4 for bottom MNGH
A-side ABCD with a 5 degree inclination, B-side EFGH parallel to A-side ABCD, with A-side ABCD arranged on the side opened at an angle of 135 degrees with respect to bottom MNGH, and bottom M
A line C parallel to the NGH and between the A-side ABCD and the bottom MNGH
A plane AB is the C plane IJKL which is the plane rotated parallel to the A plane ABCD by θ degrees about the axis MH perpendicular to D.
It is characterized by having between the CD and the B-side EFGH.

When the present μ compound prism is used in an optical head for an optical disk device that records information by changing the amount of light reflected from the disk surface such as a compact disk, the angle θ is (90−θ) degrees. At the angle of μ, the laser beam irradiated to the bottom surface MNGH from the inside of the composite prism is selected within the range where it is not totally reflected by the bottom surface MNGH.
When the compound prism is used in an optical head for a magneto-optical disk device that records information by rotating the polarization surface on the disk surface of a mini disk or the like by the Kerr effect, the angle θ is selected to be about 45 degrees. In the present embodiment, the operation when used in an optical head for an optical disc device that records information by changing the amount of reflected light from the disc surface of a compact disc or the like will be described, so the angle θ is selected to be 30 degrees. Here, the triangular prism EPH-FOG may or may not be provided. That is, it may be cut off on the B-side EFGH.

Here, when the present μ compound prism is used in an optical head for an optical disk device for recording information by changing the amount of reflected light from the disk surface of a compact disk or the like, the surface A is a half mirror and the surface B is a surface. Is a total reflection surface, and the C surface is a half mirror. Further, when the present μ composite prism is used for an optical head for a magneto-optical disk device which records information by rotating the polarization surface on the disk surface of a mini disk or the like by the Kerr effect,
The surface is a half mirror or a beam splitter, the B surface is a total reflection surface, and the C surface is a polarization beam splitter. In the present embodiment, the operation when used in an optical head for an optical disk device that records information by changing the amount of reflected light from the disk surface of a compact disk or the like will be described. Therefore, the A surface is a half mirror and the B surface is Total reflection surface,
Each of the C surfaces is composed of a half mirror.

Here, when the 3-beam tracking method is used, a 3-beam grating pattern is formed in the region MNCD in the bottom surface. In this embodiment, since one beam tracking is used, the above 3
The beam grating pattern is not formed.

2 to 4 show the arrangement of the μ compound prism and the optical components in the optical head of this embodiment. In these figures, FIG. 2 is a vertical sectional view showing the above optical arrangement, FIG. 3 is a top view thereof, and FIG. 4 is a transverse sectional view thereof. 2 to 4, 201 is the μ shown in FIG.
It is a compound prism. 202 is an A-side half mirror of the μ compound prism, 203 is a B-side total reflection surface of the μ compound prism, 204 is a C face half mirror of the μ compound prism, and 205 is an upper face of the μ compound prism. 20
6 is the bottom surface of the μ compound prism. Reference numeral 210 denotes a laser light source, which is arranged so that the laser beam 211 is incident on the μ composite prism 201 from the bottom surface 206 and is irradiated to the A surface 202 at an angle of 45 degrees. The A surface 202 is a half mirror, and a part of the laser beam with which the A surface is irradiated is transmitted as it is.

Reference numeral 212 denotes an objective lens, which focuses the laser beam 211 transmitted through the A surface 202 and incident on a light spot 213. The light spot 213 is the objective lens 21.
2 is the focus direction 214 and the tracking direction 215
It is positioned on the information track on the optical disk by moving it to. The reflected light reflected by the information track on the optical disk passes through the objective lens 212 and is incident on the upper surface 205 of the μ compound prism and is irradiated on the A surface 202. Since the A surface is a half mirror, a part of the reflected light applied to the A surface is reflected by the A surface and becomes the optical axis 216 and is guided to the B surface 203 and the C surface 204.

C-plane 204 is a half mirror, and C-plane 2
A part of the optical axis 216 irradiated on 04 is transmitted through the C surface to become the optical axis 217 and is irradiated on the B surface. The optical axis 217 irradiated on the B surface is totally reflected toward the bottom surface 206 of the μ compound prism and is irradiated on the light receiving element A 219. At this time, with respect to the optical path length from the light source 210 to the A surface 202, the A surface 202
The dimension of the μ composite prism is selected so that the optical path length from the light receiving element to the light receiving element A 219 is longer.

A part of the optical axis 216 is reflected by the C surface 204 to become the optical axis 218. Since the C surface 204 rotates by θ degrees about the optical axis 216 as the center of rotation, the optical axis 218 enters the bottom surface 206 at an angle of (90−θ) degrees. At this time, the angle θ is selected so that the optical axis 218 is not totally reflected by the bottom surface 206. In this embodiment, θ is selected to be 30 degrees. The optical axis 218 transmitted through the bottom surface 206 is the light receiving element B22.
It is irradiated to 0. At this time, the size of the μ compound prism is selected so that the optical path length from the A surface 202 to the light receiving element B 220 is shorter than the optical path length from the light source 210 to the A surface 202. Here, the laser light source 201 and the light receiving element A
219 and the light receiving element B220 are integrally formed or fixed on the same substrate as a light emitting and receiving module.

FIG. 5 shows the shape of the light receiving element in the optical head of this embodiment and the positional relationship of the reflected light from the disk irradiated onto the light receiving element. In FIG. 5, 3
Reference numeral 01 denotes a light receiving element A, which has a light receiving region 302,
The light receiving area 303 and the light receiving area 304 are divided into three areas. Reference numeral 305 is a light spot A of the reflected light from the optical disc irradiated onto the light receiving element A through the B surface of the μ compound prism. On the light receiving element A301, the light spot A305 straddles 303, and is 302, 303, and 304.
, And the center of 305 is located on 303.

Reference numeral 306 denotes a light receiving element B, which has a light receiving area 307, a light receiving area 308 + 309, and
The light receiving area 310 is divided into three areas, and the light receiving area 30 is further divided.
8 + 309 is divided into light receiving regions 308 and 309 in the X direction. Reference numeral 311 denotes a light spot B of the reflected light from the optical disc irradiated onto the light receiving element B through the C surface of the μ compound prism. On the light receiving element B306, the light spot B311 straddles 308 and 309 and crosses 307, 308, and 3
09 and 310 are irradiated and the center of 311 is 308
It is located above the border of 309 and 309.

Reference numeral 312 is a summing amplifier,
A signal 313 is generated by adding the outputs of the light receiving elements 4, 307, and 310. 314 is a summing amplifier,
The output of the light receiving elements 308 and 309 is added to generate 315. A differential amplifier 316 generates a difference signal between the output of the light receiving element 303 and the output 315 of the addition amplifier 314. A differential amplifier 319 generates a difference signal of the outputs of the light receiving elements 308 and 309.

The operation of the first embodiment will be described next. As shown in FIGS. 2 to 4, the laser beam 211 emitted from the laser light source 210 is focused on the information track on the optical disc by the objective lens 212. The reflected light of the laser beam 211 reflected on the information track is again incident on the μ compound prism via the objective lens 212. The reflected light is applied to the light receiving element A 219 and the light receiving element B 220 by the A surface 202, the C surface 204, and the B surface 203 of the μ compound prism.

In FIG. 2, from the light source 210 to the A side 202
Up to the optical path length from the A surface 202 to the light receiving element A 219
The dimension of the μ composite prism is selected so that the optical path length from the light source 210 to the A surface 202 is longer than the optical path length from the A surface 202 to the light receiving element B 220. Since the size of the μ composite prism is selected so as to be shorter, when the light spot 213 is deviated to the laser light source 210 side in the focus direction 214 with respect to the information track, in FIG. The light spot 305 becomes smaller, and the ratio of light irradiated to the light receiving region 303 becomes larger, so that the detection output of 303 becomes larger. Further, the light spot 311 on the light receiving element B306 becomes large, and the ratio of irradiation to the light receiving regions 308 and 309 becomes small, so that the detection outputs of 308 and 309 become small. Therefore, the differential signal 317 obtained by subtracting the addition signal 315 of the detection outputs of 308 and 309 from the detection signal of 303.
Grows. On the contrary, in FIG. 2, when the light spot 213 is displaced toward the disc side in the focus direction 214 with respect to the information track, the differential signal 317 becomes small. Therefore, if the light spot 213 is moved in the focus direction 214 so that the differential signal 317 has a predetermined value, the light spot 213 can be focused on the information track.

In FIG. 2, the tracking direction is 215.
Therefore, the laser beam reflected by the information track contains the first-order diffracted light diffracted in the direction 215 by the information track. Since the tracking direction 215 is the X direction on the μ compound prism, in FIG. 5, the light spot 311 on the light receiving element B includes the first-order diffracted light by the information track in the X direction. Therefore, if the light spot 213 is moved in the tracking direction 215 so that the differential signal 319 between the light receiving regions 308 and 309 divided in the X direction becomes a predetermined value, the light spot 213 performs the tracking operation on the information track. You can

The present embodiment is used for an optical head for an optical disk device which records information by changing the amount of reflected light from the disk surface of a compact disk or the like. In FIG. 5, since the light spots 305 and 311 contain the information recorded in the information track on the optical disc as the light amount change, the addition output 313 can reproduce the information on the information track.

In order to perform the focusing operation,
In FIG. 5, it is necessary to position the center of the light spot 305 in the Y direction on the light receiving region 303 and the center of the light spot 311 in the Y direction on the light receiving region 308 + 309. In FIG. 3, if the μ compound prism 201 is rotated on the XY plane with the laser light source 210 as the center of rotation,
The light spot on the light receiving element A219 can be positioned at a desired position in the Y direction. Further, in FIG.
Even if the compound prism 201 is moved in parallel in the X direction, the position of the light spot on the light receiving element A 219 does not move because the A surface 202 and the B surface 203 are parallel to each other. When the μ compound prism 201 is moved in parallel in the X direction, the A surface 202 and the B surface 203 are parallel to each other, and the C surface 204 is rotated about the optical axis 216 about the surfaces parallel to the A surface and the B surface. Since the light spots on the light receiving element B220 can be moved only in the Y direction without moving in the X direction, the light spot on the light receiving element B220 can be moved to the desired position in the Y direction. Can be positioned at.

In order to perform the tracking operation, it is necessary to position the center of the light spot 311 in the X direction at the boundary between the light receiving regions 308 and 309 in FIG. 2 and 4, even if the μ compound prism 201 is translated in the Y direction, the position of the light spot on the light receiving element A 219 does not move because the A surface 202 and the B surface 203 are parallel to each other. In addition, the μ composite prism 201 is set to Y
By parallel translation in the direction, the A surface 202 and the B surface 203 are parallel to each other, and the C surface 204 is a surface parallel to the A surface and the B surface, which is a surface rotated with respect to the optical axis 216. Since the position of the light spot on the light receiving element B220 can be moved only in the X direction without moving in the Y direction, the light spot on the light receiving element B220 can be positioned at a desired position in the X direction.

As described above, according to the first embodiment, the optical component is integrated with the μ composite prism, and the laser light source and the two light receiving elements are combined into a compact light emitting / receiving module, so that the laser Since the optical component (μ compound prism) can be attached to the position where the diameter of the laser beam is small in the vicinity of the light source, the size of the optical component can be made small. Purpose) can be achieved.

Further, according to the first embodiment, the light receiving element B is irradiated with the positional relationship between the position of the laser light source and the position of the light spot irradiated on the light receiving element A being kept constant. Since the position of the light spot to be moved can be adjusted by moving the entire μ compound prism, it is not necessary to individually position and adjust the laser light source and the light receiving element with respect to the optical system as in the conventional optical head. The light source and the two light receiving elements can be integrated into a compact light emitting and receiving module. In this case, even if the assembly accuracy of the light emitting and receiving module is low, it is only necessary to adjust the position of the μ composite prism.
An optical head can be provided at low cost. In addition, the optical components are integrated into the μ composite prism, and the light emitting and receiving components are integrated into the light receiving and emitting module, reducing the number of parts.
Purpose of providing an inexpensive optical head (second purpose)
Can be achieved.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. FIG. 6 shows the structure of the μ composite prism used in the present embodiment. The μ composite prism 501 has bottom surfaces MN2 parallel to each other.
G2H and ABOP on top, 4 for bottom MN2G2H
A-side ABC1C2D and A-side ABC1C2D with 5 degree inclination
Is arranged on the side opened at an angle of 135 degrees with respect to the bottom surface MN2G2H and is parallel to the A surface ABC1C2D and the B surface EFG1G2H
And parallel to the bottom surface MN2G2H, the A surface ABC1C2D and the bottom surface MN2G2
A-plane A with the axis MH perpendicular to the line of intersection DC2 with H as the center of rotation
C plane I, which is the plane rotated by θ1 degrees parallel to BC1C2D
JK1K2L is provided between the A side ABC1C2D and the B side EFG1G2H, and the D side N2N1G3G2, which is at least a part of the side on which the distance between the A side ABC1C2D and the C side IJK1K2L is large, is the bottom surface M.
It is characterized in that an angle ∠M N2N1 with respect to N2G2H forms an angle θ2 of 90 degrees or more and 135 degrees or less. In the present embodiment, θ1 = 45 degrees and θ2 = 135 degrees are selected.

Here, surface EFOP, surface POG3G2H, surface E
There may or may not be a three-dimensional portion consisting of the PH, the surface FOG3G1, the surface G1G2G3, and the B surface EFG1G2H. That is, side B E
It may be cut off with FG1G2H.

Here, when the present μ compound prism is used for an optical head for an optical disk device which records information by changing the amount of reflected light from the disk surface such as a compact disk, the surface A is a half mirror and the surface B is a surface. Is a total reflection surface, and the C surface is a half mirror. Further, when the present μ composite prism is used for an optical head for a magneto-optical disk device which records information by rotating the polarization surface on the disk surface of a mini disk or the like by the Kerr effect,
The surface is a half mirror or a beam splitter, the B surface is a total reflection surface, and the C surface is a polarization beam splitter.

In the present embodiment, since it is used for an optical head for a magneto-optical disk device which records information by rotating the polarization plane on the disk surface of a mini disk or the like by the Kerr effect, the A surface is the beam splitter, The surface B is a total reflection surface, and the surface C is a polarization beam splitter. The D surface is a transparent surface.

Here, when the 3-beam tracking method is used, a 3-beam grating pattern is formed in the area MN2C2D in the bottom surface. In this embodiment, since three-beam tracking is used, a three-beam grating pattern is formed in the area so that the laser beam is divided into three beams in the direction of the axis MH.

7 to 9 show the arrangement of the μ compound prism and the optical components in the optical head of this embodiment. In these figures, FIG. 7 is a vertical sectional view showing the above optical arrangement, FIG. 8 is a top view thereof, and FIG. 9 is a transverse sectional view thereof. 7 to 9, 501 is the μ shown in FIG.
It is a compound prism. 502 is an A-plane polarization beam splitter of the μ compound prism, 503 is a B-plane total reflection surface of the μ compound prism, 504 is a C surface polarizing beam splitter of the μ compound prism, and 505 is an upper surface of the μ compound prism. Yes, 506 is the bottom surface of the μ compound prism, and
Reference numeral 07 is a D-side transmissive surface of the μ composite prism, and 508 is μ
It is a 3 beam grating pattern on a compound prism.

Reference numeral 510 denotes a laser light source, which is arranged so that the laser beam 511 enters the μ compound prism 501 from the bottom surface 506 and irradiates the A surface 502 at an angle of 45 degrees. Further, the laser light source 510 is arranged so that the polarization plane of the laser beam 511 which is linearly polarized light is P-polarized light 511P having an oscillation axis parallel to the plane A of incidence which is a beam splitter.

Since the three-beam grating pattern 508 is formed in the portion of the bottom surface 506 of the μ compound prism where the laser beam 511 is incident, the laser beam 511 has a total of three main beams and two sub-beams in the X direction. Is split into. When the main beam is on the information track, the spectral direction is set so that the sub-beam slightly shifts from the center of the information track.

The A-plane beam splitter 502 transmits part of P-polarized light (linearly polarized light having an oscillation axis parallel to the incident surface of the beam splitter) and S-polarized light (linearly polarized light having an oscillation axis perpendicular to the incident surface of the beam splitter). ) Is totally reflected. Since the laser beam 511 applied to the surface A is the P-polarized light 511P, part of it is transmitted as it is.

Reference numeral 512 denotes an objective lens, which focuses the laser beam 511 which is transmitted through the A surface 502 and is incident on a light spot 513. The light spot 513 is the objective lens 51.
By moving 2 in the focus direction 514 (Z direction) and the tracking direction 515 (Y direction), positioning is performed on the information track on the optical disc. Laser beam 51
When reflected by the information track on the optical disc, the reference numeral 1 is reflected light 511S whose vibration axis is rotated by .theta.K by the information pit recorded magneto-optically. The reflected light 511S passes through the objective lens 512 and is incident on the upper surface 505 of the μ compound prism and is irradiated on the A surface 502. A part of the reflected light 511S irradiated on the A surface is reflected on the A surface and becomes an optical axis 516.
It is guided to the surface 503 and the C surface 504.

The C surface 504 is rotated by θ1 degrees with respect to the optical axis 516. Here, when the present μ compound prism is used in an optical head for an optical disc device that records information by changing the amount of light reflected from a disc surface such as a compact disc, it is reflected by the C surface 504 and irradiated on the D surface 507. The angle .theta.1 is selected so that the optical axis 518 irradiates the light receiving element B520 within an angle range in which the light receiving element B520 has sufficient light receiving sensitivity. If θ1 is reduced, the bottom surface 506
Since the irradiation angle of the light receiving element B520 located in parallel with the vertical angle approaches the vertical, the light receiving sensitivity is improved. When the present μ composite prism is used in an optical head for a magneto-optical disk device that records information by rotating the polarization surface on the disk surface of a mini disk or the like by the Kerr effect, the angle θ
Choose 1 for 45 degrees. In the present embodiment, the operation when used in an optical head for a magneto-optical disk device that records information by rotation of the polarization plane on the disk surface of a mini disk or the like due to the Kerr effect will be described.
I choose every time.

The C surface 504 is a polarization beam splitter, which transmits only P-polarized light and reflects S-polarized light. C side 50
4 is rotated by θ 1 = 45 degrees with respect to the optical axis 516, and the incident surface is rotated by 45 degrees with respect to the main polarization plane of the optical axis 516 which is linearly polarized light. Therefore, the light amount of the optical axis 516 is equally divided. Then, half of the light is transmitted and irradiated to the B surface, and half is reflected and becomes the optical axis 518. The optical axis 517 irradiated on the B surface is totally reflected toward the bottom surface 506 of the μ compound prism and is irradiated on the light receiving element A 519. At this time, from the light source 510 to the A surface 5
For the optical path length up to 02, from the A surface 502 to the light receiving element A5
The dimensions of the μ compound prism are selected so that the optical path length up to 19 is longer.

Half of the optical axis 516 is reflected by the C surface 504 and becomes the optical axis 518. Since the C surface 504 is rotated about the optical axis 516 by 45 degrees, the optical axis 518 passes through the D surface 507 having an angle of θ 2 with respect to the bottom surface 506 and is irradiated to the light receiving element B 520. In this embodiment, since θ2 = 135 degrees is selected, the optical axis 518 is the D plane 5
The light beam is incident on 07 at a right angle and is irradiated onto the light receiving element B520 at an angle of 45 degrees. When the light receiving element B does not have sufficient light receiving sensitivity at an irradiation angle of 45 degrees and it is necessary to make the irradiation angle close to 90 degrees, if θ2 is made smaller than 135 degrees, the optical axis 5 is reduced.
Since 18 is refracted toward the bottom surface 506 side when passing through the D surface 507, the irradiation angle of the optical axis 518 with respect to the light receiving element B520 can be brought close to 90 degrees.

At this time, the dimensions of the μ composite prism are selected so that the optical path length from the A surface 502 to the light receiving element B 520 is shorter than the optical path length from the light source 510 to the A surface 502. Here, the laser light source 501 and the light receiving element A51
9 and the light receiving element B520 are integrally formed or fixed as a light receiving and emitting module on the same substrate.

FIG. 10 shows the shape of the light receiving element in the optical head of this embodiment and the positional relationship of the reflected light from the disk irradiated on the light receiving element. Reference numeral 601 denotes a light receiving element A, which has light receiving regions 602, 603 + 60 in the X direction.
It is divided into 3 regions of 4 + 606 and 607.
Further, 603 + 604 + 606 is 603,6 in the Y direction.
It is divided into three areas 04 and 606. 608
Is the light spot of the main beam of the reflected light from the optical disc. Reference numerals 609 and 610 denote sub-beam light spots. The light spot 608 straddles 604 and is 60
3, 604 and 606 are illuminated and the center of 608 is located on 604. Light spots 609 and 610 are projected onto 602 and 607, respectively.

Further, reference numeral 611 denotes a light receiving element B, which has light receiving regions 612, 613 + 614 + 616, and in the X direction.
It is divided into three areas 617. Furthermore, 613 + 61
4 + 616 is 613, 614, and 616 in the Y direction.
It is divided into three areas. Reference numeral 618 denotes a light spot of the main beam of the reflected light from the optical disc. 619
And 620 are light spots of sub-beams. The light spot 618 straddles 614, and 613, 614, and
Illuminates 616 and the center of 618 is located above 614. Light spots 619 and 620 are 612 and 61, respectively.
7 is illuminated.

Reference numeral 621 denotes a differential amplifier, which is a light receiving element A6.
01 main beam detection output (603 + 606) and light receiving element B 611 main beam detection output (613).
+616) to generate a difference signal 622. Reference numeral 623 denotes an adding amplifier, which is a sum signal 62 of the main beam detection output (603 + 606) on the light receiving element A601 and the main beam detection output (613 + 616) on the light receiving element B611.
4 is generated. 625 is a differential amplifier, which is a light receiving element A
A difference signal 626 between the detection output 604 of the central portion of the main beam on 601 and the detection output 614 of the central portion of the main beam on the light receiving element B 611 is generated. Reference numeral 627 denotes a differential amplifier, which is a detection output 6 obtained by dividing the main beams 608 and 618 on the light receiving elements A601 and B611 in the Y direction.
For 03, 606, 613, and 616, (60
A difference signal 628 between (3 + 616) and (606 + 613) is generated. 629 is a differential amplifier, which is a light receiving element A60
1 and subbeams 609, 610, 61 on B611
9 and 620 detection outputs 602, 607, 612,
And about 617, (602 + 612) and (607
+617) to generate a difference signal 630.

The operation of the second embodiment will be described next. As shown in FIG. 7, the laser beam 511 emitted from the laser light source 510 has an objective lens 512.
Is focused on the information track on the optical disc.
The reflected light, which is the laser beam 511 reflected on the information track, is incident on the μ compound prism again via the objective lens 512. The reflected light is A of the μ composite prism.
The light receiving element A 519 and the light receiving element B 520 are irradiated with the surface 502, the C surface 504, and the B surface 503.

In FIG. 7, from the light source 510 to the A surface 502.
For the optical path length up to the light receiving element A519
The dimension of the μ composite prism is selected so that the optical path length from the light source 510 to the A surface 502 is longer than the optical path length from the A surface 502 to the light receiving element B 520. Since the size of the μ compound prism is selected so as to be shorter, when the light spot 513 is deviated to the laser light source 510 side in the focus direction 514 with respect to the information track, the light spot on the light receiving element A 601 in FIG. The light spot 608 becomes smaller, and the ratio of irradiation to the light receiving region 604 becomes larger, so that the detection output of 604 becomes larger. Further, the light spot 318 on the light receiving element B 611 becomes large, and the ratio of irradiation to the light receiving region 614 becomes small, so the detection output of 614 becomes small. Therefore, the differential signal 626 becomes large. On the contrary, in FIG.
When 13 is displaced toward the disc side in the focus direction 514 with respect to the information track, the differential signal 626 becomes small. Therefore, if the light spot 513 is moved in the focus direction 514 so that the differential signal 626 has a predetermined value, the light spot 513 can be focused on the information track.

7 and 9, the laser beam 511 is split into a total of three beams, that is, a main beam and two sub beams. When the main beam is on the information track, the sub beam is slightly displaced from the center of the information track. Therefore, in FIG. 10, the detection output (602 + 61) that receives the reflected light from each of the two sub-beams is obtained.
Tracking control can be performed by the differential signals 630 of 2) and ((607 + 617).

In FIG. 7, the tracking direction is 515.
Therefore, the laser beam reflected by the information track contains the first-order diffracted light which is diffracted in the direction of 515 by the information track. Since the tracking direction 215 is the Y direction on the μ compound prism, the light spots 608 and 618 on the light receiving elements A and B in FIG. 10 include the first-order diffracted light by the information track in the Y direction. Therefore, the detection outputs (603 + 616) and (606 + 61) obtained by dividing the light spots 608 and 618 into two in the Y direction, respectively.
It is possible to detect a wobble signal recorded from the differential signal 628 of 3) by utilizing the fact that the first-order diffracted light changes due to the wobble of the information track.

This embodiment is used for an optical head for a magneto-optical disk device which records information by rotating the polarization plane on the disk surface of a mini disk or the like due to the Kerr effect.
In FIG. 7, the optical axis 51, which is the reflected light from the optical disk,
Reference numeral 6 includes information recorded in the information track on the optical disc as rotation of the polarization plane ± θk, and also includes optical intensity variation due to intensity variation of the emitted light of the laser light source and reflectance variation on the optical disc. . The polarization beam splitter C plane 504 on which the optical axis 516 is incident has an optical axis 516.
It is rotated by 45 degrees with respect to the optical axis 51 which is linearly polarized light.
Since the incident surface is rotated by 45 degrees with respect to the main polarization plane of No. 6, the light transmitted through the C surface 504 and the reflected light have the same DC component due to the fluctuation of the light intensity, and the signal component due to the polarization plane rotation ± θk. Is in reverse phase. The light transmitted through the C surface 504 is applied to the light receiving element A 519, and the light reflected by the C surface 504 is applied to the light receiving element B 520. Therefore, in FIG. 10, the detection output of the main beam on the light receiving element A (603+
The signal magneto-optically recorded on the information track on the optical disk can be reproduced from the difference signal 622 between the detection output (613 + 616) of the main beam on the light receiving element B611.

Further, since the reflected light from the optical disc also includes the change in the amount of reflected light from the optical disc surface, in FIG. By using the sum signal 624 with the detection output (613 + 616), it is possible to reproduce the information signal from the optical disc that records information by the change in the amount of reflected light from the disc surface such as a compact disc.

In order to perform the focusing operation and the wobble signal detection operation, in FIG. 10, the center of the light spot 608 in the Y direction is positioned in the light receiving area 604, and the center of the light spot 618 in the Y direction is located in the light receiving area 614.
Need to be positioned. 7 and 8,
The μ composite prism 501 is used as the laser light source 51 on the XY plane.
By rotating it around 0 as a rotation center, the light spot on the light receiving element A 519 can be positioned at a desired position in the Y direction. Further, in FIG. 7, the μ composite prism 501
Even if it is translated in the X direction, the A side 502 and the B side 503
Since and are parallel to each other, the position of the light spot on the light receiving element A519 does not move. In addition, μ composite prism 5
If 01 is translated in the X direction, A surface 502 and B surface 5
03 is parallel to each other, and the C surface 504 is a surface parallel to the A surface and the B surface rotated with respect to the optical axis 516. Therefore, the position of the light spot on the light receiving element B520 is set in the X direction. Since it can be moved only in the Y direction without moving, the light spot on the light receiving element B520 can be positioned at a desired position in the Y direction.

As described above, according to the second embodiment, the optical component is integrated with the μ composite prism, and the laser light source and the two light receiving elements are combined into a compact light emitting / receiving module. Since the optical component (μ compound prism) can be attached to the position where the diameter of the laser beam is small in the vicinity of the light source, the size of the optical component can be made small. Purpose) can be achieved.

Further, according to the second embodiment, the light receiving element B is irradiated with the positional relationship between the position of the laser light source and the position of the light spot irradiated on the light receiving element A kept constant. Since the position of the light spot to be moved can be adjusted by moving the entire μ compound prism, it is not necessary to individually position and adjust the laser light source and the light receiving element with respect to the optical system as in the conventional optical head. The light source and the two light receiving elements can be integrated into a compact light emitting and receiving module. In this case, even if the assembly accuracy of the light emitting and receiving module is low, it is only necessary to adjust the position of the μ composite prism.
An optical head can be provided at low cost. In addition, the optical components are integrated into the μ composite prism, and the light emitting and receiving components are integrated into the light receiving and emitting module, reducing the number of parts.
Purpose of providing an inexpensive optical head (second purpose)
Can be achieved.

According to the second embodiment, instead of rotating the polarization plane of the optical axis incident on the polarization beam splitter by 45 degrees, the polarization beam splitter itself is rotated by 45 degrees with respect to the optical axis. Therefore, it is possible to achieve the object (third object) of providing an inexpensive optical head capable of detecting a magneto-optical signal without using a half-wave plate made of an expensive crystal material. ..

Further, according to the second embodiment, since the three-beam grating pattern is integrally provided on the surface of the μ compound prism on which the laser beam is incident from the laser light source, the structure is compact. The object (fourth object) of providing a small-sized optical head capable of performing three-beam tracking can be achieved.

(Third Embodiment) A third embodiment of the present invention will be described below with reference to the drawings. FIG. 11 shows the structure of the μ compound prism used in this embodiment. The μ composite prism 801 has bottom surfaces MN parallel to each other.
GH and top ABOP, 4 for bottom MNGH
A-side ABCD with a 5 degree inclination, B-side EFGH parallel to A-side ABCD, with A-side ABCD arranged on the side opened at an angle of 135 degrees with respect to bottom MNGH, and bottom M
Parallel to NGH, intersection line D between A-side ABCD and bottom MNGH
A plane parallel to the A plane with the axis MH perpendicular to C as the center of rotation is θ
The C surface IJKL that is rotated by 1 degree is provided between the A surface ABCD and the B surface EFGH, and the A surface ABCD and the C surface IJK
D, which is at least a part of the side surface with the larger distance from L
The angle ∠MNB is 45 with respect to the surface NBOG with respect to the bottom surface MNGH.
The angle θ2 is not less than 90 degrees and not more than 90 degrees.
In the present embodiment, θ1 = 45 degrees and θ2 = 67.5 degrees are selected. Where surface EFOP, surface POGH, surface EP
There may or may not be a three-dimensional portion composed of H, plane FOG, and B plane EFGH. That is, it may be cut off on the B-side EFGH.

Here, when the present μ compound prism is used for an optical head for an optical disk device for recording information by changing the amount of reflected light from the disk surface of a compact disk or the like, the surface A is a half mirror and the surface B is a surface. Is a total reflection surface, and the C surface is a half mirror. Further, when the present μ composite prism is used for an optical head for a magneto-optical disk device which records information by rotating the polarization surface on the disk surface of a mini disk or the like by the Kerr effect,
The surface is a half mirror or a beam splitter, the B surface is a total reflection surface, and the C surface is a polarization beam splitter. In the present embodiment, since it is used for an optical head for a magneto-optical disk device that records information by rotation of the polarization plane on the disk surface of a mini disk or the like due to the Kerr effect, the A surface is a beam splitter and the B surface is The total reflection surface and the C surface are each composed of a polarization beam splitter. The D surface is a total reflection surface.

Here, when the 3-beam tracking method is used, a 3-beam grating pattern is formed in the region MNCD in the bottom surface. In this embodiment, since three-beam tracking is used, a three-beam grating pattern is formed in the area so as to divide the laser beam into three beams in the direction of the axis DC.

12 to 15 show the arrangement of the μ compound prism and the optical components in the optical head of this embodiment. In these figures, FIG. 12 is a vertical cross-sectional view showing the optical arrangement, FIG. 13 is a top view of the same, FIG. 14 is a horizontal cross-sectional view of the same on the light emitting side, and FIG. 15 is a horizontal cross-sectional view of the same on the light receiving side. 12 to 15, reference numeral 801 denotes the same μ compound prism as shown in FIG. 802
Is an A-plane beam splitter of μ compound prism,
3 is the B-side total reflection surface of the μ compound prism, and 804 is μ
It is a C-plane polarization beam splitter of a compound prism.
Reference numeral 5 is the upper surface of the μ compound prism, 806 is the bottom surface of the μ compound prism, 807 is the D-side reflecting surface of the μ compound prism, and 808 is the three-beam grating pattern on the μ compound prism.

Reference numeral 810 denotes a laser light source, which is arranged so that the laser beam 811 is reflected by the mirror 821, is incident on the μ compound prism 801 from the bottom surface 806, and is irradiated to the A surface 802 at an angle of 45 degrees. It The laser light source 810 is a laser beam 81 that is a linearly polarized light.
The polarization plane of No. 1 is arranged so as to be P-polarized light 811P having an oscillation axis parallel to the plane A of incidence which is the beam splitter. Since the three-beam grating pattern 808 is formed in the portion of the bottom surface 806 of the μ composite prism where the laser beam 811 is incident, the laser beam 811 is split into a main beam and two sub-beams in the Y direction, that is, a total of three beams. It When the main beam is on the information track, the spectral direction is set so that the sub-beam slightly shifts from the center of the information track.

The A-plane beam splitter 802 transmits part of P-polarized light (linearly polarized light having an oscillation axis parallel to the incident surface of the beam splitter) and S-polarized light (linearly polarized light having an oscillation axis perpendicular to the incident surface of the beam splitter). ) Is totally reflected. Since the laser beam 811 with which the surface A is irradiated is the P-polarized light 811P, a part of the laser beam 811 is transmitted as it is. A part of the light is reflected and irradiated on the reflection surface 809, and then reflected by the reflection surface 809 and irradiated on the light receiving element 823. Here, the reflecting surface 809 may be integrally formed with the μ composite prism 801, or may be separately assembled.

Reference numeral 812 denotes an objective lens, which focuses a laser beam 811 which is transmitted through the A surface 802 and is incident on a light spot 813. The light spot 813 is the objective lens 81.
By moving 2 in the focus direction 814 (Z direction) and the tracking direction 815 (X direction), positioning is performed on the information track on the optical disc. Laser beam 81
When reflected by the information track on the optical disk, 1 becomes reflected light 811S whose vibration axis is rotated by .theta.K by the information pits recorded magneto-optically. The reflected light 811S is incident on the upper surface 805 of the μ compound prism through the objective lens 812 and is irradiated on the A surface 802. A part of the reflected light 811S irradiated on the A surface is reflected on the A surface and becomes an optical axis 816.
It is guided to the surface 803 and the C surface 804.

The C surface 804 is rotated by θ1 with respect to the optical axis 816. In the present embodiment, the operation when used in an optical head for a magneto-optical disk device that records information by rotation of the polarization plane on the disk surface of a mini disk or the like due to the Kerr effect will be described. I choose every time. The C plane 804 is a polarization beam splitter,
Only P-polarized light is transmitted and S-polarized light is reflected. The C plane 804 is rotated by θ 1 = 45 degrees with respect to the optical axis 816, and the incident plane is 4 with respect to the main polarization plane of the optical axis 816 which is linearly polarized light.
Since it is rotated 5 degrees, the light amount of the optical axis 816 is divided into equal parts, half of which is transmitted and irradiated to the B surface, and half of which is reflected and reflected by the optical axis 81.
It becomes 8. The optical axis 817 irradiated on the B surface is totally reflected toward the bottom surface 806 of the μ compound prism, and the light receiving element A 81
Irradiated to 9. At this time, the dimensions of the μ composite prism are selected so that the optical path length from the A surface 802 to the light receiving element A819 is longer than the optical path length from the light source 810 to the A surface 802.

Further, half of the optical axis 816 is reflected by the C surface 804 and becomes the optical axis 818. Since the C surface 804 is rotated about the optical axis 816 by 45 degrees, the optical axis 818 is reflected by the D surface 807 having an angle of θ2 with respect to the bottom surface 806, and θ3 = (θ1 + 2θ2) on the light receiving element B820. -90) Irradiation is performed at an angle of (degrees). Θ1 is selected to be 45 degrees in order to divide the optical axis 816 into equal parts so as to optimize the detection characteristics of the magneto-optical signal, but by selecting θ2 to an appropriate value, the light receiving element B820 has sufficient light receiving sensitivity. The optical axis 818 can be irradiated onto the light receiving element B820 within the irradiation angle range. In the present embodiment, by selecting θ2 = 67.5 (degrees), the irradiation angle becomes θ3 = 90 (degrees), and the optical axis 818 is irradiated perpendicularly to the light receiving element B820.

At this time, the dimensions of the μ compound prism are selected so that the optical path length from the A surface 802 to the light receiving element B 820 is shorter than the optical path length from the light source 810 to the A surface 802.

Here, the laser light source 801 and the mirror 82
1, the light receiving element A 819, the light receiving element B 820, and the light receiving element 823 are integrally formed or fixed on the same semiconductor substrate 822 as a light receiving and emitting module. The light receiving element A 819, the light receiving element B 820, and the light receiving element 823, which are photodiodes, are formed on the semiconductor substrate 822 by a semiconductor process. A mirror 821 having an angle of 45 degrees with respect to the surface is used, and a laser beam 811 emitted from a laser light source 810, which is a laser diode, is applied to the concave portion by the mirror 8.
It is arranged so that it is reflected by 21 and rises perpendicularly to the surface of the semiconductor substrate 822.

FIG. 16 shows the shape of the light receiving element in the optical head of this embodiment and the positional relationship of the reflected light from the disk irradiated onto the light receiving element. Reference numeral 901 denotes a light receiving element A, which has light receiving regions 902, 903, 90 in the Y direction.
It is divided into five areas of 4, 906, and 907.
Reference numeral 908 denotes the light spot of the main beam of the reflected light from the optical disc. Reference numerals 909 and 910 denote sub-beam light spots. The light spot 908 straddles 904 and is applied to 903, 904, and 906.
The center of is located on 904. Light spots 909 and 9
10 is illuminated on 902 and 907 respectively.

Reference numeral 911 denotes a light receiving element B, which has light receiving regions 912, 913, 914 + 915, 91 in the Y direction.
It is divided into 5 areas of 6 and 917. Furthermore, 9
14 + 915 is divided into two regions 914 and 915 in the X direction. Reference numeral 918 denotes a light spot of the main beam of the reflected light from the optical disc. 919 and 920
Is the light spot of the sub-beam. The light spot 918 straddles 914 + 915, and 913, 914, 915,
And 916, and the center of 918 is 914 + 91.
Located above 5. Light spots 919 and 920 are 9 each
12 and 917 are illuminated.

Reference numeral 921 denotes a differential amplifier, which is a light receiving element A9.
01 main beam detection output (903 + 906) and the main beam detection output on the light receiving element B911 (913).
+916) to generate a difference signal 922. Reference numeral 923 denotes an addition amplifier, which is a sum signal 92 of the main beam detection output (903 + 906) on the light receiving element A 901 and the main beam detection output (913 + 916) on the light receiving element B 911.
4 is generated. 925 is a differential amplifier, which is a light receiving element A
A difference signal 926 is generated between the detection output 904 of the central portion of the main beam on 901 and the detection output 914 + 915 of the central portion of the main beam on the light receiving element B911. 927
Is a differential amplifier, and detection outputs 914 and 915 obtained by dividing the main beam 918 on the light receiving element B911 in the X direction.
Difference signal 928 is generated. Reference numeral 929 denotes a differential amplifier, which is a sub beam 90 on the light receiving elements A901 and B911.
Detection outputs 902 of 9, 910, 919, and 920,
For 907, 912, and 917, (902 + 9
12) and the difference signal 930 of (907 + 917) is generated.

Next, the operation of the third embodiment will be described. As shown in FIG. 12, a laser light source 810
A part of the laser beam emitted from is reflected by the reflecting surface 809 and is applied to the light receiving element 823. Light receiving element 82
The intensity of the laser beam 811 can be kept constant by controlling the output of the laser light source so that the detection output of No. 3 becomes a predetermined value. Further, as shown in FIGS. 12 and 14, the laser beam 811 emitted from the laser light source 810 is focused on the information track on the optical disc by the objective lens 812. Laser beam 8
The reflected light reflected by the information track 11 on the information track is again incident on the μ composite prism via the objective lens 812. The reflected light is applied to the light receiving element A819 and the light receiving element B820 by the A surface 802, the C surface 804, and the B surface 803 of the μ compound prism.

In FIG. 12, from the light source 810 to the A surface 80
For the optical path length up to 2, the light receiving element A81 from the A surface 802
The dimension of the μ composite prism is selected so that the optical path length up to 9 is longer, and the optical path length from the light source 810 to the A surface 802 is smaller than the optical path length from the A surface 802 to the light receiving element B820. Since the size of the μ composite prism is selected so that the shorter one, the light spot 813 is shifted to the laser light source 810 side in the focus direction 814 with respect to the information track, and on the light receiving element A901 in FIG. The light spot 908 becomes smaller and the ratio of the light received on the light receiving region 904 becomes larger, so the detection output of 904 becomes larger. In addition, a light spot 918 on the light receiving element B911
Becomes larger, and the ratio of irradiation to the light receiving areas 914 + 915 becomes smaller, so the detection output of 914 + 915 becomes smaller. Therefore, the differential signal 926 becomes large. On the contrary, in FIG. 12, when the light spot 813 is displaced toward the disc side in the focus direction 814 with respect to the information track,
The differential signal 926 becomes smaller. Therefore, the differential signal 926
When the light spot 813 is moved in the focus direction 814 so that the light spot 813 becomes a predetermined value, the light spot 813 can be focused on the information track.

In FIGS. 12 and 15, the laser beam 811 is split into a total of three beams, that is, the main beam and the sub beam. When the main beam is on the information track, the sub beam is slightly displaced from the center of the information track. Therefore, in FIG. 16, the detection outputs (902) respectively receiving the reflected lights from the two sub-beams are received.
Tracking control can be performed by the differential signals 930 of +912) and (907 + 917). See also FIG.
At 2, the tracking direction is 815, so the laser beam reflected by the information track contains first order diffracted light that is diffracted by the information track in the direction of 815. Since the tracking direction 815 is the X direction on the μ composite prism, in FIG. 16, the light spot 918 on the light receiving element B includes the first-order diffracted light by the information track in the X direction. Therefore, from the differential signals 928 of the respective detection outputs 914 and 915 obtained by dividing the light spot 918 into two in the X direction, the wobble signal recorded by detecting that the first-order diffracted light changes due to the wobble of the information track is detected. You can do it.

The present embodiment is used for an optical head for a magneto-optical disk device which records information by rotating the polarization plane on the disk surface of a mini disk or the like due to the Kerr effect.
In FIGS. 12 and 15, the optical axis 816, which is the reflected light from the optical disc, includes the information recorded in the information track on the optical disc as the rotation of the polarization plane ± θk, and at the same time, the intensity of the emitted light itself of the laser light source. It also includes light intensity fluctuations due to fluctuations and reflectance fluctuations on the optical disk.
Polarization beam splitter C plane 80 on which the optical axis 816 is incident
4 is rotated by 45 degrees with respect to the optical axis 816, and the incident surface is 45 with respect to the main polarization plane of the optical axis 816 which is linearly polarized light.
Since the light transmitted through the C surface 804 and the light reflected by the C surface 804 have the same DC component due to the fluctuation of the light intensity, the signal components due to the polarization plane rotation ± θk have opposite phases. The light transmitted through the C surface 804 is applied to the light receiving element A 819, and the light reflected on the C surface 804 is applied to the light receiving element B 820. Therefore,
16, the difference signal 9 between the detection output of the main beam on the light receiving elements A and B (903 + 906) and the detection output of the main beam on the light receiving element B911 (913 + 916)
It is possible to reproduce the signal magneto-optically recorded from 22 to the information track on the optical disk.

Further, the reflected light from the optical disc includes a change in the amount of reflected light from the optical disc surface. Therefore, in FIG. 16, the sum signal 92 of the main beam detection output (903 + 906) on the light receiving element A 901 and the main beam detection output (913 + 916) on the light receiving element B 911.
4 can be used to reproduce an information signal from an optical disc such as a compact disc which records information by changing the amount of reflected light from the disc surface.

In order to perform the focusing operation,
In FIG. 16, it is necessary to position the center of the light spot 908 in the Y direction on the light receiving area 904 and the center of the light spot 918 in the Y direction on the light receiving areas 914 + 915. In FIG. 13, if the μ compound prism 801 is rotated around the laser light source 810 on the XY plane, the light spot on the light receiving element A819 can be positioned at a desired position in the Y direction. Further, in FIG. 13, even if the μ compound prism 801 is translated in the X direction, the position of the light spot on the light receiving element A819 does not move because the A surface 802 and the B surface 803 are parallel to each other. If the μ compound prism 801 is moved in parallel in the X direction, the A surface 802 and the B surface 803 will be parallel to each other,
Since the surface C parallel to the surfaces A and B is the surface rotated with respect to the optical axis 816, the position of the light spot on the light receiving element B820 is not moved in the X direction, but only in the Y direction. Since it can be moved to, the light spot on the light receiving element B820 can be positioned at a desired position in the Y direction.

In order to perform the wobble signal detecting operation, it is necessary to position the center of the light spot 918 in the X direction at the boundary between the light receiving regions 914 and 915 in FIG. In FIG. 12, even if the μ compound prism 801 is translated in the Y direction, the position of the light spot on the light receiving element A819 does not move because the A surface 802 and the B surface 803 are parallel to each other. In addition, the μ composite prism 801 is set to Y
By parallel translation in the direction, the A surface 802 and the B surface 803 are parallel to each other, and the C surface 804 is a surface parallel to the A surface and the B surface rotated with respect to the optical axis 816. Since the position of the light spot on the light receiving element B820 can be moved only in the X direction without moving in the Y direction, the light spot on the light receiving element B820 can be positioned at a desired position in the X direction.

As described above, according to the third embodiment, on the light receiving element B, the positional relationship between the position of the laser light source and the position of the light spot irradiated on the light receiving element A is kept constant. It is possible to adjust the position of the light spot to be irradiated on the μ composite prism by moving it. Therefore, it is necessary to position and adjust the laser light source and the light receiving element individually with respect to the optical system like the conventional optical head. In addition, the laser light source and the two light receiving elements can be integrated into a compact light emitting and receiving module. In this case, even if the assembly accuracy of the light emitting and receiving module is low, it is only necessary to adjust the position of the μ composite prism, so the light emitting and receiving module does not require a high degree of assembly processing accuracy, reducing the assembly adjustment man-hours, and reducing the cost. An optical head can be provided.
Further, the optical component is integrated with the μ composite prism, and the light emitting / receiving component is integrated with the light emitting / receiving module to reduce the number of components and achieve an object (second object) of providing an inexpensive optical head. Can be done.

Further, according to the third embodiment, the optical components are integrated with the μ composite prism, and the laser light source and the two light receiving elements are combined into a compact light emitting / receiving module. Since an optical component (μ compound prism) can be attached at a position where the diameter of the laser beam is small, it is possible to reduce the size of the optical component, and thus to provide a small optical head (first purpose). Can be achieved.

According to the third embodiment, instead of rotating the polarization plane of the optical axis incident on the polarization beam splitter by 45 degrees, the polarization beam splitter itself is rotated by 45 degrees with respect to the optical axis. Therefore, it is possible to achieve the object (third object) of providing an inexpensive optical head capable of detecting a magneto-optical signal without using a half-wave plate made of an expensive crystal material. .

Further, according to the third embodiment, the three-beam grating pattern is integrally provided on the surface of the μ composite prism on which the laser beam is incident from the laser light source, so that the structure is compact. The object (fourth object) of providing a small-sized optical head capable of beam tracking can be achieved.

Further, according to the third embodiment, the optical system for guiding the laser beam from the laser light source to the disk and the optical system for guiding the reflected light from the disk to the light receiving element are all composed of the reflecting surface and the straight transmitting surface. Since all optical axis directions are geometrically determined and there is no part that determines the optical axis direction by refraction, there is no change in laser wavelength due to temperature fluctuations or laser output power fluctuations. It is possible to achieve the object (fifth object) of providing an optical head in which axis deviation does not occur.

Further, according to the third embodiment, a part of the laser beam emitted from the laser light source reflected by the surface A which is the half mirror or the beam splitter of the μ compound prism is used for the output monitor of the laser light source. By using it as a beam, it is possible to provide a compact optical head that has a compact structure and can control the laser output constantly. Further, since a light receiving element for receiving the output monitoring beam can be integrated with the light emitting / receiving module, an object is to provide a compact optical head having a compact structure and capable of controlling the laser output at a constant level. Purpose) can be achieved.

[0117]

As described above, according to the present invention,
By integrating the optical components that guide the laser beam into a single μ-composite prism, the optical component (μ-composite prism) can be attached near the laser light source at a position where the diameter of the laser beam is small. It is possible to reduce the size of the device, and it is possible to provide a small optical head.

Further, the position of the optical axis B irradiated on the light receiving element B is μ-complexed while the positional relationship between the position of the laser light source and the position of the optical axis A irradiated on the light receiving element A is kept constant. Since it can be adjusted by moving the entire prism, it is only necessary to adjust the position of the μ composite prism on the light receiving and emitting module (laser light source and assembly of two light receiving elements) assembled with low accuracy. This has the effect of reducing the number of assembly and adjustment steps and providing an inexpensive optical head.

Since the polarization beam splitter itself is rotated by 45 degrees with respect to the optical axis instead of rotating the polarization plane of the optical axis incident on the polarization beam splitter by 45 degrees, it is made of an expensive crystal material. It is possible to detect a magneto-optical signal without using the ½ wavelength plate described above, and thus it is possible to provide an inexpensive optical head.

Further, the three-beam grating pattern is integrally provided on the surface on which the laser beam is emitted from the laser light source of the μ composite prism.
It has an effect that it is possible to provide a small-sized optical head capable of 3-beam tracking with a compact structure.

Further, the optical system for guiding the laser beam from the laser light source to the disk and the optical system for guiding the reflected light from the disk to the light receiving element are all made up of a reflecting surface and a straight transmitting surface, and the directions of all optical axes are geometric. Since there is no part that determines the direction of the optical axis by refraction, there is an effect that the deviation of the optical axis due to the fluctuation of the laser wavelength caused by the temperature fluctuation or the laser output power fluctuation does not occur. ..

Further, a part of the laser beam emitted from the laser light source reflected by the surface A which is the half mirror or the beam splitter of the μ compound prism is used as a beam for monitoring the output of the laser light source, so that the structure is compact. It is possible to provide a small optical head capable of controlling the laser output constantly. Further, since the light receiving element for receiving the output monitoring beam can be integrated with the light emitting / receiving module, it is possible to provide a small optical head having a compact structure and capable of controlling the laser output at a constant level. Have.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a μ compound prism according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional view for explaining the arrangement of a μ compound prism and an optical diameter according to the first embodiment of the present invention.

FIG. 3 is a top view illustrating a μ compound prism and an arrangement of optical diameters according to the first embodiment of this invention.

FIG. 4 is a cross-sectional view illustrating the arrangement of a μ compound prism and an optical diameter according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a divided region of the light receiving element and a signal arithmetic circuit according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of a μ compound prism according to a second embodiment of the present invention.

FIG. 7 is a vertical cross-sectional view illustrating a μ compound prism and an arrangement of optical diameters according to a second embodiment of the present invention.

FIG. 8 is a top view for explaining the arrangement of the μ compound prism and the optical diameter according to the second embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating the arrangement of a μ compound prism and an optical diameter according to the second embodiment of the present invention.

FIG. 10 is a diagram illustrating a divided region of a light receiving element and a signal arithmetic circuit according to a second embodiment of the present invention.

FIG. 11 is a diagram illustrating a configuration of a μ compound prism according to a third embodiment of the present invention.

FIG. 12 is a vertical cross-sectional view illustrating a μ compound prism and an arrangement of optical diameters according to a third embodiment of the present invention.

FIG. 13 is a top view illustrating a μ compound prism and an arrangement of optical diameters according to a third embodiment of the present invention.

FIG. 14 is a lateral cross-sectional view on the light emitting side for explaining the arrangement of the μ compound prism and the optical diameter according to the third embodiment of the present invention.

FIG. 15 is a transverse cross-sectional view on the light receiving side for explaining the arrangement of the μ compound prism and the optical diameter according to the third embodiment of the present invention.

FIG. 16 is a diagram illustrating a divided area of a light receiving element and a signal arithmetic circuit according to a third embodiment of the present invention.

FIG. 17 is a diagram illustrating a configuration of a conventional optical head.

[Description of Reference Signs] ABOP Upper surface MNGH Bottom ABCD surface A EFGH surface B IJKL surface C 201 μ Compound prism 202 μ Compound prism A surface 203 μ Compound prism B surface 204 μ Compound prism C surface 205 μ Compound prism upper surface 206 Bottom surface of μ composite prism 210 Laser light source 211 Laser beam 212 Objective lens 213 Light spot 214 Focusing direction 215 Tracking direction 216 Reflected light from the optical disk directed to the detection optical system at the A surface 217 Reflected light from the optical disk transmitted through the C surface 218 Reflected light from optical disc reflected on C surface 219 Light receiving element A 220 Light receiving element B 301 Light receiving element A 302 Light receiving element A divided area 303 Light receiving element A divided area 304 Light receiving element A divided area 305 μ Composite prism B Optical disc reflected by the surface Reflected light from 306 Light receiving element B 307 Dividing area 308 of light receiving element B 308 Dividing area of light receiving element B 309 Dividing area of light receiving element B 310 Dividing area of light receiving element B 311 μ From the optical disk reflected on the C surface of the composite prism Reflected light 312 Output of addition amplifier 313 312 (RF sum signal) 314 Output of addition amplifier 315 314 316 Output of differential amplifier 317 316 (focus error signal) 318 Output of differential amplifier 319 316 (tracking error signal)

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 12-7/22

Claims (8)

(57) [Claims] 1. A μ compound prism having a bottom surface and a top surface which are parallel to each other, wherein a surface A having an inclination of 45 degrees with respect to the bottom surface and a surface A opened at an angle of 135 degrees with respect to the bottom surface. And a plane B parallel to the plane A arranged on the side and a plane parallel to the bottom plane and perpendicular to the intersection line between the plane A and the bottom plane as a rotation center are rotated at an angle smaller than 90 degrees . A μ composite prism having a surface C, which is a surface between surfaces A and B, a laser light source, two or more light receiving elements, and an objective lens are provided, and the laser beam emitted from the laser light source is An optical head for reading / writing data from / to an optical disk by using a light spot which is incident on the objective lens through a μ compound prism and is condensed on the optical disk. 2. A μ compound prism having a bottom surface and a top surface which are parallel to each other, wherein a surface A having an inclination of 45 degrees with respect to the bottom surface and a surface A opened at an angle of 135 degrees with respect to the bottom surface. And a plane B parallel to the plane A arranged on the side and a plane parallel to the bottom plane and perpendicular to the intersection line between the plane A and the bottom plane as a rotation center are rotated at an angle smaller than 90 degrees . The surface C, which is a surface, is located between the surfaces A and B, and the surface D, which is at least a part of the side surface having the larger distance between the surfaces A and C, is 90 degrees or more and 135 degrees or less with respect to the bottom surface. And a laser light source, two or more light receiving elements, and an objective lens, and a laser beam emitted from the laser light source is passed through the μ compound prism. Using the light spot that is incident on the objective lens and focused on the optical disc An optical head for reading and writing data to the optical disc. 3. A μ compound prism having a bottom surface and a top surface which are parallel to each other, wherein a surface A having an inclination of 45 degrees with respect to the bottom surface and a surface A opened at an angle of 135 degrees with respect to the bottom surface. And a plane B parallel to the plane A arranged on the side and a plane parallel to the bottom plane and perpendicular to the intersection line between the plane A and the bottom plane as a rotation center are rotated at an angle smaller than 90 degrees . The surface C, which is a surface, is located between the surfaces A and B, and the surface D, which is at least a part of the side surface having the larger distance between the surfaces A and C, exceeds 45 degrees with respect to the bottom surface, and 90 The μ compound prism is characterized by forming an angle of less than 100 degrees, a laser light source, two or more light receiving elements, and an objective lens. The light spot which is incident on the objective lens via the There, the optical head for reading and writing data to the optical disc. 4. The surface of the μ compound prism is a half mirror, the surface B is a total reflection surface, and the surface C is a half mirror.
4. The optical head according to any one of 3 to 3. 5. The surface C of the μ compound prism is a surface obtained by rotating the surface parallel to the surface A by 45 degrees about an axis parallel to the bottom surface of the μ compound prism and perpendicular to the line of intersection of the surface A and the bottom surface. The surface A is composed of a half mirror or a polarization beam splitter, the surface B is composed of a total reflection surface, and the surface C is composed of a polarization beam splitter so that a magneto-optical signal can be reproduced. The optical head according to any one of claims 1 to 3, which is characterized in that. 6. A three-beam tracking is possible by integrally forming a diffraction grating on a surface of a μ compound prism on which a laser beam is incident from a laser light source. The described optical head. 7. A direction parallel to the bottom surface of the μ compound prism and perpendicular to a line of intersection of the surface A and the low surface is defined as a major axis direction, and a direction parallel to the bottom surface and perpendicular to the major axis direction is defined as the μ compound prism. When the minor axis direction is used, the laser output can be controlled to a constant value by providing a reflecting surface having an angle of 40 to 50 degrees with the lower surface including the minor axis direction on the side where the surface A forms an angle of 45 degrees with the bottom surface. The optical head according to any one of claims 1 to 3, characterized in that. 8. A direction parallel to the bottom surface of the μ compound prism and perpendicular to the line of intersection of the surface A and the lower surface is defined as a major axis direction, and a direction parallel to the bottom surface and perpendicular to the major axis direction is defined as the μ compound prism. When the minor axis direction is adopted, the reflected light of the light receiving element A and the surface C arranged to receive the reflected light of the surface B or the reflected light of the surface C whose direction is changed by the surface D is received. And a light receiving element B arranged, the light receiving element A is divided only in the long axis direction of the μ compound prism, and the light receiving element B is divided in the long axis direction and the short axis direction of the μ compound prism. The optical head according to any one of claims 1 to 3, wherein the optical head is provided.