JPH11345443A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of optical components and to miniaturize and lighten an optical pickup by providing a spectral part light guiding to a polarized light separating part light dividing a laser beam emitted from a light receiving/emitting part onto a magneto-optical disk and passing through a through hole and also light dividing the laser beam reflected from the magneto-optical disk. SOLUTION: The laser beam emitted from a laser diode 21 in a magneto-optical hologram unit 20 passes through the through holes of polarized light separating functional elements 30, 35, and passes through a hologram optical element 26 to be converted to a parallel beam by a collimator lens 16 and to be reflected to a right angular direction by a rise mirror 17. The reflected laser beam is converged by an objective lens 18, and is reflected from the signal recording surface of the magneto- optical disk 15 to become the laser beam having a signal and to return through the same optical path. The returned laser beam is bent to two directions by the hologram surface of the hologram optical element 26, and are light divided further to four directions by the polarized light surfaces of the polarized light separating functional elements 30, 35, and arrive at the light receiving part 50 to be converted to an electric signal and to be taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup used for reading data recorded on a magneto-optical disk in an optical disk device, and more particularly to an optical pickup suitable for miniaturization.

[0002]

2. Description of the Related Art A conventional optical pickup for a magneto-optical disk will be described with reference to FIG. FIG. 6 is a configuration diagram showing an optical system of a conventional optical pickup. Reference numeral 100 denotes an optical system of an optical pickup used for a conventional magneto-optical disk, and all of the optical components configured are of a discrete type using individual single components. The main optical components include a laser diode 110 serving as a light source, a diffraction grating 115 for separating (diffracting) laser light into three or more laser lights for detecting a tracking error signal, and a laser diode 110 serving as a light source. The laser light emitted from the optical disk 120 is reflected, and the light reflected by the magneto-optical disk 120 is transmitted to separate the going laser light and the returning laser light. Then, the magneto-optical disk is used to detect a focus error signal. A beam splitter 125 having a function of generating astigmatism with respect to a return light (transmitted light) from the laser 120, a collimating lens 130 for converting laser light emitted from the laser diode 110 as divergent light into parallel light, A photoelectric conversion element that receives light and outputs a signal corresponding to the amount of light,
Detector 135 that outputs control signals of various servo systems
And the laser light emitted from the laser diode 110 of the light source is divided into two for the light amount detection light and the light to the magneto-optical disk 120, and the return light reflected by the magneto-optical disk 120 is used for the magneto-optical signal detection. And a beam splitter 140 having a non-polarized characteristic that separates the laser light into light for forming a control signal of a servo system, and among the laser lights emitted from the light source, receives light separated by the beam splitter 140 for light amount detection. A detector 1 for outputting a signal for an APC (auto power control circuit) for controlling the light emission intensity by changing the amount of current of the laser diode 110 according to the light amount
45, a polarization separation function element 150 that separates the light separated for detection of a magneto-optical signal by the beam splitter 140 from the return light from the magneto-optical disk 120 according to the polarization plane of the light, A condensing lens 155 for connecting the light separated accordingly to a light spot on the light receiving unit;
A detector 160 for a magneto-optical signal, which outputs a signal for reproducing a signal recorded on a magneto-optical disk by a photoelectric conversion element which receives the light condensed in 5 and outputs a signal corresponding to the amount of light; A rising mirror 165 that bends an optical path originally formed perpendicular to the magneto-optical disk 120 to reduce the thickness of the device, and a laser beam that is incident as parallel light on the pit surface of the magneto-optical disk 120 by about 1 μm. 1 such as the objective lens 170 that narrows down to the beam spot diameter of
It is composed of two optical components.

[0003]

However, in the case of the above-mentioned discrete type optical pickup, the problem with the number of optical components to be constituted is that the number of components is particularly large, and the mounting accuracy of each optical component and each optical component are problematic. Due to the holding members and the like required for mounting the parts, the cost is increased due to adjustment or improvement of the precision of the individual parts, and the cost is increased due to an increase in the number of assembling work steps and an increase in the difficulty of the work contents. Also, in the optical pickup, due to its component configuration, the difference is much larger than the added function compared with an optical disk device that does not read a magneto-optical signal, and there is a problem that the entire optical pickup becomes large and heavy. . In addition, there has been a problem that the area occupied by the optical system in the optical pickup due to the amount of bending of the optical path is larger than that of an optical system that does not read a normal magneto-optical signal.

An object of the present invention is to solve the above-mentioned problems, and to provide an inexpensive optical pickup in which the number of optical components to be constituted is reduced, the size and weight are reduced.

[0005]

According to the present invention, there is provided an optical pickup for reading data recorded on a magneto-optical disk, comprising: a laser emitting section for emitting a laser beam; A light receiving / emitting unit mounted with a light receiving unit for receiving the laser light reflected by the light emitting unit and outputting an electric signal; and a passage through which the laser light emitted from the light receiving / emitting unit to the magneto-optical disk is adjacent to the light receiving / emitting unit. A polarization separating unit having a hole, separating the laser light reflected by the magneto-optical disk according to the plane of polarization thereof, and guiding the laser light to the corresponding light receiving element; And a spectroscopy section for splitting the laser light emitted from the optical disk to the magneto-optical disk and passing through the passage hole, and guiding the laser light reflected by the magneto-optical disk to the polarization separation section. It is characterized in.

Further, the through hole is formed so as not to block a laser beam which is not blocked by an optical system from the light emitting section to the light receiving section. Further, the polarized light separating section is constituted by a plurality of polarized light separating pieces.
In addition, an annular projection is formed at the light-receiving / light-emitting-portion-side opening of the passage hole, the inner wall being a surface continuous with the passage hole, and the outer wall coinciding with a part of a side surface of a cone having the light-emitting portion as a vertex. It is characterized by having.

[0007] Further, the shape and the spectral direction of the light of the split polarization splitting piece are symmetric with respect to a plane including the laser light emitted from the light emitting / receiving section to the magneto-optical disk. It is characterized by the following. Further, the surface on the light receiving / emitting section side of the polarized light separating section is subjected to a non-transmissive process that hardly transmits laser light.

[0008] Further, between the polarization splitting section and the splitting section,
A space is provided. Further, the light-splitting unit and the light-splitting unit have the same light-splitting direction, and the light-receiving unit is arranged in the same light-splitting direction.
It is characterized by comprising a plurality of light receiving elements.

[0009]

FIG. 1, FIG. 2, FIG. 3, FIG.
This will be described with reference to FIG. FIG. 1 is a configuration diagram showing an optical system of an optical pickup according to one embodiment of the present invention. FIGS. 2A and 2B are configuration diagrams showing a beam splitting unit of the optical system according to the present embodiment, in which FIG. 2A is a diagram showing a split state of return light, and FIG. FIG. 3 is a plan view showing the structure of the light receiving section in this embodiment. 4A and 4B are diagrams illustrating another configuration example of the polarization beam splitting function element according to the present embodiment, in which FIG. 4A is a front cross-sectional view, and FIG. FIG. 5 is a plan view showing another configuration example of the polarization beam splitting function element according to the present embodiment.

Reference numeral 10 denotes an optical system included in an optical pickup for a magneto-optical disk.
And four optical components such as a collimator lens 16, a rising mirror 17, and an objective lens 18.
The magneto-optical hologram unit 20 is emitted from a laser diode 21 serving as a light source, a diffraction grating for separating (diffracting) the laser light into three or more laser lights for detecting a tracking error signal, and a laser diode 21 serving as a light source. The laser light is reflected, and the reflected and returned light from the magneto-optical disk 15 is transmitted to separate outgoing and returning laser light. Then, the magneto-optical disk 15 is used for focus error signal detection. Control of various servo systems by a beam splitter having a function of generating astigmatism with respect to return light 24 (transmitted light) from the camera, and a photoelectric conversion element for receiving the return light 24 and outputting a signal corresponding to the amount of light. The laser light emitted from the detector for outputting the signal and the laser diode 21 as the light source is divided into two for the light amount detection light and the light for the magneto-optical disk 15. And a non-polarized beam splitter for separating return light 24 reflected by the magneto-optical disk 15 into light for detecting a magneto-optical signal and light for forming a control signal for a servo system, and a light splitter having a non-polarized light. APC (auto power control circuit) for controlling the light emission intensity by receiving the light separated by the beam splitter for the light amount detection and changing the current amount of the laser diode 21 in accordance with the light amount. A detector that outputs a signal, and a polarization separation function element 30 that separates light separated for detection of a magneto-optical signal by a beam splitter among return light 24 from the magneto-optical disk 15 according to the polarization plane of the light,
35 and a photoelectric conversion element that outputs a signal corresponding to the light amount, and a component having a function such as a magneto-optical signal detector that outputs a signal for reproducing a signal recorded on the magneto-optical disk 15 is integrally configured. Have been.

Reference numeral 25 denotes a part of the light splitting unit of the optical system, which is a part of a hologram optical element (reciprocating separation element) 26 whose surface is subjected to hologram processing and polarization separation function elements 30 and 35 composed of a Wollaston prism and the like. , The polarization separation function elements 30 and 35 and the hologram optical element 26
A space 60 is provided between the two. Each of the polarization separation function elements 30 and 35 has a through hole 31 (a hole formed by the concave portions 32 and 36) through which the outgoing laser light 23 emitted from the laser diode 21 serving as a light source to the magneto-optical disk 15 passes. Is formed. In addition, the passage hole 31
Is formed so as not to block the laser beam passing through the dimension D of the diaphragm portion 19 of the objective lens 18, even if the objective lens 18 is swung in the radial direction by the maximum amount within the movable range. It is formed in a size that does not block the laser beam passing through the diaphragm 19 of the objective lens 18.
When the return light 24 from the magneto-optical disk 15 is split into lights 28 and 29 by the hologram surface 27 of the hologram optical element 25, the separation angle further increases when passing through the space 60. Then, the return light 24 whose separation angle is widened is further increased by the polarization planes 33 and 37 of the polarization separation function elements 30 and 35.
(40, 41, 42, 43) and each reaches each detector pattern of four regions.

Reference numeral 50 denotes a case where the return light 24 is polarized light separating function element 3.
The light is further split into four light beams (4
0, 41, 42, and 43), and a plurality of lines 55, 56, and 57 in which detector patterns (51, 52, 53, and 54) of four regions are aligned on the same line in the light receiving unit (this embodiment) 3) are formed. The light receiving unit 50 converts a received light amount into an electric signal and sets a focus servo for focusing on a disk reflection surface, a tracking servo for following a predetermined track, a laser output servo for keeping a laser diode oscillation output constant, and a disk motor. Servo systems such as a linear velocity driven CLV servo and an optical system feed servo for moving the optical pickup body are adjusted.
In order to facilitate the formation of the detector pattern, the detector patterns in four regions are provided such that the S-polarized light 51 and 52 are on the outside and the P-polarized light 53 and 54 are on the inside. However, out of the three detector pattern lines, 1
Except for the book (center) line, the other two lines correspond to the upper left patterns 51 and 53 and the lower patterns 51 and 53, respectively.
3 may be formed on the lines connected to each other, or the upper right patterns 52 and 54 may be formed on the lines connecting the lower patterns 52 and 54 respectively.

Next, another configuration example of the polarization splitting function element will be described. Reference numeral 70 denotes a polarization separation function element, which is constituted by a Wollaston prism or the like, and has a central portion formed with a through hole 71 through which laser light 23 emitted from the laser diode 21 serving as the light source 22 to the magneto-optical disk 15 passes.
The size of the passage hole 71 is determined by the aperture 1 of the objective lens 18.
9 is formed so as not to block the laser beam passing through the dimension D of the objective lens 9 even if the objective lens 18 is swung in the radial direction by the maximum amount within the movable range.
The laser beam that passes through the aperture section 19 of FIG. In addition, an annular projection 72 whose outer wall coincides with a part of the side surface of the cone having the light source 22 as an apex is formed on the opening on the light source side of the passage hole 71 at a surface continuous with the passage hole 71. Instead of forming the annular projection 72, a non-transmissive process (for example, as shown in FIG.
5) may be applied. In addition, a paint may be applied to the portion, or coloring or the like may be applied.

Reference numeral 16 denotes a collimating lens which converts laser light emitted from the laser diode 21 as divergent light into parallel light. Reference numeral 17 denotes a rising mirror, which is a mirror that bends and polarizes an optical path originally formed perpendicular to the magneto-optical disk 15 to reduce the thickness of the device, and has a reflecting surface inclined at 45 degrees to the beam incident angle direction. I have.

Reference numeral 18 denotes an objective lens which narrows down the laser light that has entered as parallel light onto the signal recording surface of the magneto-optical disk 15 to a beam spot diameter of about 1 μm. Next, the operation of the optical system of the optical pickup will be described. The laser light 23 emitted from the light source (semiconductor laser chip) 21 in the magneto-optical hologram unit 20
The light passes through the hologram optical element 25 through the through holes 31 of the polarization splitting function elements 30 and 35, is converted into parallel light by the collimating lens 16, and is reflected by the rising mirror 17 in a right angle direction (toward the objective lens 21). The reflected laser light is converged by the objective lens 18 into a beam spot having a diameter of about 1 μm, and the condensed laser light is reflected by the signal recording surface of the magneto-optical disk 15 to become a laser light having a signal and the same optical path. And returns to the laser hologram unit 25. Then, the returned laser beam 24 is split by the hologram surface 26 of the hologram optical element 25 and is
When the light passes through the polarization splitting function elements 30 and 35, the light is further split by the polarization planes 33 and 37 into four directions (40, 41, 42, and 43), and is divided into four areas of the detector pattern 51. The light reaches the photoelectric conversion element connected to 52, 53, and 54, and is converted into an electric signal and taken out.

As described above, according to this embodiment, M
By forming the O optical system (magneto-optical hologram unit 20) into a single package, the number of optical components is reduced, the arrangement of the optical components is simplified, assembly adjustments and the like are facilitated, and costs can be reduced. Further, the size of the optical pickup can be reduced, and the size and weight of the entire device can be reduced. Further, it is possible to cope with high-speed access. Further, the polarization separation function element 30,
Passage holes 31 and 7 through which laser light 23 on the outward path passes at 35 and 70
By forming the projections 1 and the protrusions 72 or the matte surface 75 at the opening on the light source side in the passage hole 71, it becomes a simple countermeasure against stray light and is hardly affected by the polarization splitting element.
Further, since the space 60 is provided between the hologram optical element (reciprocating separation element) 26 and the polarization separation function elements 30 and 35, the light split into two light beams on the hologram surface 27 passes through the space 60. In this case, since the separation angle is further increased, the interference between the laser beam transmitting portion and the return light 24 is reduced.
Further, the detector patterns 5 of the four regions are arranged in the same direction as the light split into four by the polarization splitting function elements 30 and 35.
By forming a plurality of lines (three lines) in which 1, 52, 53, and 54 are arranged on the same line and providing a photoelectric conversion element, it is easy to extract the MO signal. In addition, access to the focus error signal can be quickly performed.

[0017]

As described above, according to the present invention, the number of constituent optical components can be reduced, and a small and lightweight optical pickup can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an optical system of an optical pickup according to one embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a light splitting unit of the optical system according to the present embodiment.
(A) is a spectral diagram of return light, and (b) is a diagram viewed from an arrow A.

FIG. 3 is a plan view illustrating a structure of a light receiving unit in the present embodiment.

4A and 4B are diagrams showing another configuration example of the polarization beam splitting function element in the present embodiment, wherein FIG. 4A is a front cross-sectional view, and FIG.

FIG. 5 is a plan view illustrating another configuration example of the polarization beam splitting function element according to the present embodiment.

FIG. 6 is a configuration diagram showing an optical system of a conventional optical pickup.

[Explanation of symbols]

 10 Optical system 15 Magneto-optical disk 16 Collimating lens 17 Start-up mirror 18 Objective lens 19 Aperture section Reference numeral 20: magneto-optical hologram unit 21: laser diode 22: light source 23: laser light 24: return light 25: spectral part 26 ... Hologram optical element 27... Hologram surface 30, 35, 70... Polarization separation function element 31, 71.・ Concave parts 33,37 ・ ・ ・ ・ ・ ・ Polarization planes 40,41,42,43 ・ Spectrum 50 ・ ・ ・ ・ ・ ・ ・ ・ ・ Light receiving parts 51,52,53,54 ・ Detector patterns 55,56, 57 ··· Line 60 ·········· Space part 72 ··· ........ annular projection 75 .......... satin

Claims (8)

[Claims] 1. An optical pickup for reading data recorded on a magneto-optical disk, comprising: a laser light-emitting unit for emitting laser light; and a light-receiving unit for receiving the laser light reflected by the magneto-optical disk and outputting an electric signal. A light emitting and receiving unit mounted with, a light receiving and emitting unit, adjacent to the light receiving and emitting unit, has a through hole through which laser light emitted from the light receiving and emitting unit to the magneto-optical disk, the laser light reflected by the magneto-optical disk A polarization separation unit that separates according to a polarization plane and guides the light to the corresponding light receiving element; and a laser beam that is adjacent to the polarization separation unit and emitted from the light receiving / emitting unit to the magneto-optical disk and passing through the passage hole. An optical pickup comprising: a splitting unit that splits a laser beam reflected by a magneto-optical disk and guides the split laser beam to the polarization splitting unit. 2. The device according to claim 1, wherein the passage hole is formed in a size that does not block laser light that is not blocked by an optical system from the light emitting unit to the light receiving unit. Optical pickup. 3. The polarization separation unit according to claim 1, wherein the polarization separation unit includes a plurality of polarization separation pieces.
Alternatively, the optical pickup according to claim 2. 4. An annular projection whose inner wall is continuous with the through hole and whose outer wall coincides with a part of a side surface of a cone whose apex is the light emitting unit is provided at the opening on the light receiving / emitting section side in the through hole. The optical pickup according to claim 1, wherein the optical pickup is formed. 5. The split polarization beam splitter has a shape and a spectral direction of the light that are symmetric with respect to a plane including a laser beam emitted from the light emitting / receiving unit to the magneto-optical disk. The optical pickup according to claim 3, wherein: 6. The optical pickup according to claim 1, wherein a surface of the polarization splitting unit on the side of the light receiving / emitting unit is subjected to a non-transmissive process that hardly transmits laser light. 7. The optical pickup according to claim 1, wherein a space is provided between the polarization splitting unit and the light splitting unit. 8. The light-receiving device according to claim 1, wherein a light-splitting direction of the polarization splitting unit and the light-splitting unit is the same light-splitting direction, and the light-receiving unit includes four light-receiving elements arranged in the same light-splitting direction. Optical pickup.