JPH1031834A - Light emitting unit cover and optical pickup using the same - Google Patents

Abstract

(57) Abstract: A light-emitting unit cover, an optical pickup, and an optical disk device using the same, which have a simple configuration and are capable of correcting astigmatism of a light-emitting unit, which is a laser light source, at low cost and with low cost. To provide. A laser light source for emitting a laser light beam.
In the light emitting unit cover 23 formed by resin molding and covering the light emitting unit cover 2c and having a light transmitting surface perpendicular to the optical path of the laser light beam from the laser light source, the light emitting unit cover is at least at its light transmitting surface. The light emitting unit cover 23 is formed so as to be resin-molded by appropriately selecting the resin flow direction at the time of molding so as to have astigmatism that cancels out the astigmatism inherent to the laser light source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mini disc (M
D), an optical pickup for recording and / or reproducing signals from a magneto-optical disk (MO), a compact disk (CD), a CD-ROM, etc. (hereinafter, referred to as an "optical disk"), and an optical disk provided with the optical pickup The present invention relates to a device, and particularly to a light emitting element cover of an optical pickup.

[0002]

2. Description of the Related Art Conventionally, an optical pickup for an optical disk is constructed, for example, as shown in FIG. In FIG. 8, an optical pickup 1 includes an astigmatism correction plate 3, a beam splitter 4, a rising mirror 5, and a rising mirror 5, which are sequentially arranged in the optical path of a light beam emitted from a semiconductor laser element 2 as a laser light source. It comprises an objective lens 6 and a photodetector 7 disposed in a separation optical path of return light from the optical disc D reflected by the beam splitter 4.

In the optical pickup 1 having such a configuration, the light beam from the semiconductor laser element 2 passes through the astigmatism correction plate 3 and is reflected by the beam splitter 4 before being raised by the rising mirror 5 for the optical disk. The optical path is bent in the direction of D, and the optical disc D is
The signal is recorded on the signal recording surface. Then, the return light beam reflected on the signal recording surface passes through the beam splitter 4 from the objective lens 6 and the rising mirror 5 and is received by the light receiving surface of the photodetector 7 to detect a recording signal. It has become.

[0004] In order to accurately detect a reproduced signal,
In order for the light beam from the semiconductor laser element 2 to form a spot at a correct position on the signal recording surface of the optical disc D and to accurately reproduce a recorded signal, the objective lens 6
It is finely moved based on a predetermined servo signal. As the servo of the objective lens 6, the optical disk D
Tracking servo for finely moving the objective lens 6 along the radial direction of the optical disc D with respect to the recording track, and focusing for finely moving the objective lens 6 toward and away from the signal recording surface of the optical disc D along the optical axis Servo and have been done.

[0005]

By the way, in the optical pickup 1 having such a structure, the semiconductor laser element 2 is controlled by the applied current I as shown in FIG.
A plane θ1 perpendicular to the PN junction plane and a plane θ parallel to the PN junction plane
2 has different light emitting points, and thus has a unique astigmatism of, for example, about 20 μm. Therefore, if this astigmatism is left as it is,
For example, as shown in FIG. 10, the defocus amount changes due to astigmatism AS, and the bottom position of the jitter and the peak position of the traverse level are shifted.

Therefore, in order to correct this astigmatism,
The above-mentioned astigmatism correction plate 3 is disposed on the optical path obliquely with respect to the optical axis. The astigmatism correction plate 3 is usually a plate glass, and is positioned and fixed at a predetermined angle with respect to the optical axis. For this reason, there has been a problem that the component cost and the assembly cost of the astigmatism correction plate 3 are increased.

In view of the above, the present invention provides a light-emitting unit cover, an optical pickup, and a light-emitting unit, which have a simple configuration and are capable of correcting the astigmatism of a light-emitting unit as a laser light source at low cost. It is an object of the present invention to provide an optical disk device that has been developed.

[0008]

According to the present invention, there is provided, in accordance with the present invention, a laser light source for emitting a laser light beam, and a light transmission surface perpendicular to the optical path of the laser light beam from the laser light source. In the light-emitting unit cover formed by resin molding, the light-emitting unit cover has a resin at the time of molding so that the light-emitting unit cover has astigmatism at least on its light transmitting surface to offset astigmatism inherent to the laser light source. This is achieved by the resin-molded light-emitting unit cover by appropriately selecting the flow direction.

According to the above configuration, the laser light beam emitted from the laser light source passes through the light transmitting surface of the light emitting unit cover, and then forms an image on the signal recording surface of the optical disk via the objective lens. Here, since the light emitting unit cover is formed so as to have astigmatism that cancels out the astigmatism inherent in the laser light source, the astigmatism inherent in the laser light source is removed by the light emitting unit cover. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
Since the embodiments described below are preferred specific examples of the present invention, various technically preferred limitations are added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows an optical disc apparatus incorporating a light emitting unit cover and an optical pickup according to an embodiment of the present invention. In FIG. 1, an optical disk device 10 includes:
A spindle motor 12 as driving means for rotating the optical disk 11 and a signal beam are irradiated on a signal recording surface of the rotating optical disk 11 to record a signal. An optical pickup 20 for reproducing and a control unit 13 for controlling these are provided. Here, the control unit 13 includes an optical disk controller 14, a signal demodulator 15, an error correction circuit 16, an interface 17, a head access control unit 18, and a servo circuit 19.

The optical disk controller 14 controls the drive of the spindle motor 12 at a predetermined rotation speed. The signal demodulator 15 demodulates the recording signal from the optical pickup 20, corrects the error, and sends the signal to an external computer or the like via the interface 17. Thus, an external computer or the like can receive a signal recorded on the optical disk 11 as a reproduction signal.

The head access control unit 18 moves the optical pickup 20 to a predetermined recording track on the optical disk 11, for example, by a track jump or the like. At the moved predetermined position, the servo circuit 19 moves, for example, an objective lens serving as a light focusing means held by the biaxial actuator of the optical pickup 20 in the focusing direction and the tracking direction.

FIG. 2 and FIG.
2 shows an optical pickup incorporated in the optical pickup. 2 and 3, an optical pickup 20 includes a light receiving / emitting device 22 (see FIG. 4), which is provided on an optical base 21 and in which a semiconductor laser element as a laser light source and a photodetector are integrated. A light emitting unit cover 23 having a reflecting surface 23a as a light path bending mirror, a plane mirror 24 as a rising mirror and an objective lens 25 as a light focusing means, and a mechanism for moving the objective lens 25 in two axial directions. And a two-axis actuator 26.

Here, the optical elements except the objective lens 25, that is, the light emitting / receiving device 22, the light emitting unit cover 23, and the plane mirror 24 are connected to the optical disk 11 by means not shown.
Are fixedly held on an optical base 21 movably supported in the radial direction.

Here, the light emitting / receiving device 22 is configured, for example, as shown in FIG. In FIG. 4, a light emitting / receiving device 22 has a second semiconductor substrate 22b for light output mounted on a first semiconductor substrate 22a, and a semiconductor laser element 22 serving as a light emitting element on the second semiconductor substrate 22b.
c is mounted. On the first semiconductor substrate 22a in front of the semiconductor laser element 22c, a microprism 22d having a trapezoidal longitudinal section is installed with the inclined surface 22e as a semi-transmissive surface facing the semiconductor laser element 22c. . Here, the microprism 22d has a semi-transmissive film (not shown) formed on the inclined surface 22e. Accordingly, the light beam emitted from the semiconductor laser element 22c along the surface of the second semiconductor substrate 22b is reflected by the inclined surface of the microprism 22d, travels upward, and Reflective surface 23
a, the light reaches the optical disk 11 via the plane mirror 24 and the objective lens 25. Also, the optical disk 11
Return light from the signal recording surface of the optical disc through the objective lens 25, the plane mirror 24, and the reflecting surface 23 of the light emitting unit cover 23,
The light passes through the inclined surface 22e of the microprism 22d and reaches the bottom surface of the microprism 22d. The return light that has reached the bottom surface of the microprism 22d partially transmits through the bottom surface, and is partially reflected by the bottom surface, and travels toward the top surface of the microprism 22d.

Here, a first photodetector 22f is formed on the first semiconductor substrate 22a below the return light incident position of the microprism 22d. Further, the return light reflected on the bottom surface is reflected on the top surface of the microprism 22d, and is incident on the bottom surface of the microprism 22d again. A second photodetector 22g is formed on the first semiconductor substrate 22a below the bottom surface of the microprism 22d where the return light reflected by the upper surface of the microprism 22d is incident. The first photodetector 22f and the second photodetector 22g are each divided into a plurality of light receiving sections, and detection signals of the respective light receiving sections are output independently. Note that a third photodetector 22h is provided on the second semiconductor substrate 22b on the side opposite to the emission side of the semiconductor laser element 22c.
The third photodetector 22h includes a semiconductor laser element 22c
This is for monitoring the light emission intensity.

The semiconductor laser element 22c is a light emitting element utilizing the recombination light emission of a semiconductor, and is used as a laser light source.

The light emitting unit cover 23 is made of synthetic resin as shown in FIG.
The cover 23 is formed as shown in FIG.
For example, a laser light beam heading upward from the semiconductor laser element 22c enters the light emitting unit cover 23, and is internally reflected by a reflection surface 23a formed on the surface thereof.
It is configured as a so-called inner-reflection type optical path bending mirror which advances in the light emitting unit cover 23 substantially horizontally again and exits from the light emitting unit cover 23. Here, the light emitting unit cover 2
3 is formed of a transparent resin capable of transmitting a laser beam from the semiconductor laser element 22c,
By being placed at a predetermined position on the optical base 21,
The reflection surface 23a is positioned at a predetermined position.

The plane mirror 24 can be formed by inclining the triangular prism mirror shown in FIG. 2 or the plane mirror shown in FIG. The plane mirror 24 is a mirror disposed at an angle of 45 degrees on the optical base 21 so as to reflect a light beam traveling in a substantially horizontal direction from the light emitting unit cover 23 upward in the vertical direction. Has become.

The objective lens 25 is a convex lens and forms an image of light from the plane mirror 24 on a desired track on the signal recording surface of the optical disk 11.

Here, the objective lens 25 is movably supported in a biaxial direction, ie, a focusing direction and a tracking direction, by a biaxial actuator 26 as driving means for the objective lens shown in FIG. The biaxial actuator 26 is movable in two axial directions by a fixed portion 26a attached to the optical base 21 in a skew-adjusted state and two pairs of left and right elastic support members 26b parallel to the fixed portion 26a. The movable part 26c supported and the focusing coil 26d attached to the movable part 26c
And a tracking coil 26e.

On the other hand, a yoke 26f is provided on the optical base 21 so as to face the focusing coil 26d and the tracking coil 26e, and a magnet 26 mounted inside the yoke 26f.
g is provided.

Thus, when a drive current flows through the focusing coil 26d, the focusing coil 26d
Magnetic field generated by the magnet 26g and the yoke 26f
The movable portion 26c is driven in the focus direction by interaction with the magnetic flux flowing through the movable portion 26c. When a drive current flows through the tracking coil 26e, the magnetic field generated in the tracking coil 26e interacts with the magnetic flux flowing through the magnet 26g and the yoke 26f to drive the movable portion 26c in the tracking direction. Thus,
The objective lens 25 held by the movable portion 26c is driven and controlled in the biaxial directions.

Further, the light emitting unit cover 23 is configured to have astigmatism that cancels out the astigmatism inherent to the semiconductor laser element 22c. Here, the light emitting unit cover 23 is formed by determining the flow direction of the resin at the time of molding, for example, by appropriately selecting the gate position of the molding die so as to have the above-mentioned astigmatism. In this case, as the resin material, a material constituting the birefringent material, for example, Zeonex is used, but other materials having similar characteristics can be used. Thus, the light emitting unit cover 23 also has the function of the astigmatism correction plate in the conventional optical pickup.

The optical disk device 10 incorporating the optical pickup 20 according to the present embodiment is configured as described above, and operates as follows. First, the optical disk 11 is rotationally driven by the rotation of the spindle motor 12 of the optical disk device 10. Then, by moving the optical pickup 20 in the radial direction of the optical disc 11, the optical axis of the objective lens 25 is moved to a desired track position of the optical disc 11, thereby performing access.

In this state, in the optical pickup 20, the light beam from the semiconductor laser element 22c of the light receiving / emitting device 22 enters the light emitting section cover 23, and its reflection surface 2
Due to the internal reflection at 3 a, the optical path is bent and the astigmatism is corrected. After exiting from the light emitting unit cover 23, the light is reflected toward the optical disk 11 by the plane mirror 24 and passes through the objective lens 25. And the optical disk 11
Is focused on the signal recording surface. The return light from the optical disk 11 again enters the light emitting / receiving device 22 via the objective lens 25, the plane mirror 24, and the light emitting unit cover 23. The light beam that has entered the trapezoidal prism 22d of the light emitting / receiving device 22 forms an image on the photodetectors 22f and 22g. Thereby, the signal of the optical disk 11 is reproduced based on the detection signals of the photodetectors 22f and 22g.

At this time, the signal demodulator 15 is
The tracking error signal and the focusing error signal are detected based on the detection signals from f and 22g. Then, the servo circuit 19 servo-controls a drive current to the focusing coil 26d and the tracking coil 26e via the optical disk drive controller 14.
That is, the magnetic field generated in the focusing coil 26d acts on the magnetic field generated by the magnet 26g and the yoke 26f, so that the movable portion 26c is moved and adjusted in the focusing direction, and the focusing is performed. The magnetic field generated in the tracking coil 26e acts on the magnetic field generated by the magnet 26g and the yoke 26f, so that the movable portion 26c is moved and adjusted in the tracking direction, and tracking is performed.

Here, the laser light beam from the semiconductor laser element 22c of the light emitting / receiving device 22 has its astigmatism in the light emitting unit cover 23 before it enters and exits the light emitting unit cover 23. It will be offset by astigmatism. Accordingly, the light beam emitted in the horizontal direction from the light-emitting unit cover 23 has its astigmatism removed by the light-emitting unit cover 23, so that the astigmatism inherent to the laser light source becomes zero, and as shown in FIG. And the traverse level peak position coincide with each other. Thus, the traverse defect is reduced, the signal of the optical disk 11 is correctly reproduced, and the reproduction performance of the optical disk 11 is improved even if there is a defect of the optical disk such as a runout.

In this case, since the light emitting unit cover 23 also has the function of correcting astigmatism, the number of parts is reduced, and the positioning of members for correcting astigmatism is not particularly required. Assembly will be easier.

FIG. 6 shows a main part of a second embodiment of the optical pickup according to the present invention. In FIG. 6, an optical pickup 30 is replaced with a light-reflecting mirror 31 of a surface reflection type and a receiving mirror in the optical path bending mirror 31 instead of the light emitting unit cover 23 in the optical pickup 20 shown in FIGS. A light emitting unit cover 32 disposed so as to cover the light emitting device 22;
Other configurations, that is, the optical base 21, the light emitting / receiving device 22,
The plane mirror 24, the objective lens 25, and the biaxial actuator 26 have the same configuration.

Here, the optical path bending mirror 31 has a reflection surface formed on the inner surface thereof by vapor deposition of gold, aluminum, or the like in order to horizontally reflect a laser light beam traveling upward from the light emitting / receiving device 22. 31a. In this case, since the laser light beam from the light emitting / receiving device 22 does not pass through the inside of the optical path bending mirror 31, birefringence does not occur when the laser light beam passes through the inside of the optical path bending mirror 31. Further, since the light path bending mirror 31 does not need to use a translucent material, the mirror has good adhesion of a deposited film such as gold for forming the reflection surface 31a and has high moldability. It becomes possible to select a material such as polyetherimide.

The light emitting unit cover 32 is, as shown in FIG.
The light receiving / emitting device 22 as a laser light source has a light transmitting surface 32a at a predetermined distance and a leg 32b for supporting the light transmitting surface 32a on the optical base 21. The light emitting unit cover 32 is similar to the light emitting unit cover 23 in the embodiment of FIGS.
2c is formed by using a birefringent material, for example, by Zeonex so as to have astigmatism that cancels out the astigmatism inherent to 2c, and is bonded to the upper surface of the optical base 21 by, for example, an ultraviolet-curing adhesive. Attached by the agent. Thus, the light emitting unit cover 32 is sealed to the upper surface of the optical base 21 so that the optical characteristics are not affected by the stress of the adhesive.

For example, as shown by reference numeral 32c or 32d in FIG. 7, the light emitting unit cover 32 has several (two in the illustrated case) gates with respect to the molding die at the time of trial production. The light-emitting portion cover 32 formed is prepared in advance, and the molding is performed with the resin flowing direction different for each gate.
The appropriate flow direction is selected by testing the astigmatism of Thus, the light emitting section cover 32 having the desired astigmatism can be obtained. In this case, the light emitting unit cover 32 is attached to the optical base 21 immediately after the light emitting and receiving device 22 is mounted on the optical base 21, thereby protecting the light emitting and receiving device 22 in a subsequent process. Therefore, handling becomes easy.

In the optical disk device 10 and the optical pickup 20 according to the above-described embodiment, the two-axis actuator 30 is shown to be provided with the elastic support member 26b. It is obvious that the two-axis actuator of the present invention may be used.

Further, in the optical disk device 10 and the optical pickup 20 according to the above embodiment, the light receiving / emitting device 22 in which the semiconductor laser element and the photodetector are integrally formed is used as the laser light source. It is apparent that the laser light source and the photodetector may be configured separately. Further, a hologram may be used as the light separating means, or a hologram having a lens effect may be used as the light focusing means.

[0037]

As described above, according to the present invention, the light-emitting section cover and the optical pickup have a simple configuration and can correct the astigmatism of the light-emitting section as the laser light source at low cost. And an optical disk device using the same.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of an optical disk device incorporating an optical pickup according to the present invention.

FIG. 2 is a perspective view showing a configuration of an optical pickup in the optical disk device of FIG.

FIG. 3 is a side view showing a main part of an optical pickup in the optical disk device of FIG. 1;

FIG. 4 is an enlarged perspective view of a light emitting and receiving device in the optical pickup of FIG. 2;

FIG. 5 is a graph showing a relationship between a traverse level, jitter, and a defocus amount in the optical pickup of FIG. 2;

FIG. 6 is a sectional view showing a main part of a second embodiment of the optical pickup according to the present invention.

7A and 7B are a plan view and a sectional view showing a light emitting unit cover in the optical pickup of FIG.

FIG. 8 is a side view showing an optical system in an example of a conventional optical pickup.

FIG. 9 is a schematic diagram illustrating astigmatism of a semiconductor laser element in the optical pickup of FIG. 8;

FIG. 10 is a graph showing a relationship between a traverse level, jitter, and a defocus amount due to astigmatism of the semiconductor laser device of FIG. 9;

[Brief description of reference numerals]

10 optical disk device, 11 optical disk, 1
2 ... Spindle motor, 13 ... Control unit, 14.
..Optical disk drive controller, 15 ... signal demodulator, 16 ... error correction circuit, 17 ... interface, 18 ... head access control unit, 20 ...
・ Optical pickup, 21 ・ ・ ・ Optical base, 22 ・ ・
A light emitting / receiving device, 23 a light emitting unit cover, 24 a prism mirror, 25 an objective lens, 26 a biaxial actuator.

Claims (4)

[Claims] 1. A resin molding, which covers a laser light source for emitting a laser light beam and has a light transmission surface perpendicular to the optical path of the laser light beam from the laser light source.
In the light emitting unit cover, the resin flow direction at the time of molding is appropriately selected such that the light emitting unit cover has astigmatism at least on its light transmitting surface that cancels out the astigmatism inherent to the laser light source. A light-emitting unit cover characterized by being molded with a resin. 2. A laser light source for emitting a laser light beam; a light focusing means for focusing a light beam emitted from the laser light source on a signal recording surface of an optical disc; and a light source between the laser light source and the light focusing means. A light separating means provided, a light detector having a light receiving portion for receiving a return light beam from a signal recording surface of the optical disc separated by the light separating means, and a laser light source, A light-emitting unit cover formed by resin molding so as to have a light-transmitting surface perpendicular to the optical path of the laser light beam; An optical pickup characterized by being resin-molded by appropriately selecting the direction of resin flow during molding so as to have astigmatism that cancels astigmatism. 3. The light-emitting unit cover also serves as a folding mirror, and a laser beam from a laser light source enters the light-emitting unit cover and is internally reflected by a reflection surface provided on the surface. 3. The optical pickup according to claim 2, wherein the laser light beam is subsequently emitted from the light emitting unit cover. 4. A light converging means for converging a light beam emitted from a laser light source onto a signal recording surface of an optical disc; a light detecting means having a light receiving portion for receiving a return light beam from the signal recording face of the optical disc; Driving means of the light focusing means for finely moving the light focusing means, servo means for controlling the movement of the light focusing means by the driving means, and covering the laser light source and perpendicular to the optical path of the laser light beam from the laser light source. A light-emitting portion cover formed by resin molding so as to have a light-transmitting surface, wherein the light-emitting portion cover at least at the light-transmitting surface cancels out the astigmatism inherent to the laser light source. An optical disc device, which is resin-molded by appropriately selecting a resin flowing direction during molding so as to have astigmatism.