JPH0810851Y2 - Optical pickup device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an optical pickup device for optically reading out a signal recorded on a signal recording medium, and particularly uses a half mirror to divide an optical path. The present invention relates to an optical pickup device suitable for use with other devices.

(B) Conventional Technology There is a device that optically reads a signal recorded on a signal recording medium by using an optical pickup device. As a typical one of the above-mentioned devices, there is known a CD player which reproduces a compact disc (CD) in which projections called pits are formed on a signal surface in correspondence with digital signals.

In recent years, CD players have been diversified into stationary types, portable types, vehicle-mounted types and radio cassette built-in types. The portable player, the car-mounted type, and the radio cassette built-in type CD player each require a small device, and the optical pickup device is not provided with a sufficient space like a stationary CD player. With the diversification of the above, optical pickup devices have been downsized. Therefore, the number of optical pickup devices using a half mirror has increased. That is, since the half mirror can split the optical path and generate astigmatism in the reflected light from the signal surface, if the half mirror is used instead of the conventionally used half prism, the astigmatism is reduced. This is because it is possible to omit the cylindrical lens that has the ability to collect light in only one direction for generating aberration.

By the way, as described above, astigmatism occurs in the light transmitted through the half mirror, so that an optical pickup device using the half mirror causes astigmatism in the light beam applied to the disc for reading a signal. A light source is arranged so that the light beam is projected from the direction in which the optical axis is parallel to the signal surface of the disc (the reflection direction of the half mirror) so that the light beam is reflected by the surface of the half mirror. Are projected perpendicularly to the signal surface.

FIG. 4 is a model diagram showing an optical system of an optical pickup device using a general half mirror. Since the optical parts constituting the optical system are required to have a high accuracy of mounting position, they are usually arranged at a predetermined position by a base (not shown) made of aluminum die cast.

The light beam (laser light) generated from the laser diode (1) is diffracted by the diffraction grating (2) and formed into three beams of a main beam and two sub-beams (light beams used for tracking control). Surface of the half mirror (4) tilted by 45 ° with respect to the optical axis of the light beam and also tilted by 45 ° with respect to the disk (3) placed parallel to the optical axis. And the optical axis becomes perpendicular to the signal surface of the disc (3). The light beam reflected by the half mirror (4) is collimated by a collimator lens (5) and then incident on an objective lens (6), converged by the objective lens (6), and disc (3). ) Is irradiated to the signal surface. The light beam applied to the signal surface is reflected by the signal surface, and returns as reflected light to the half mirror (4) via the objective lens (6) and the collimator lens (5), and the half mirror ( 4) is transmitted. At this time, astigmatism is generated in the reflected light due to the thickness of the half mirror (4), the refractive index, and the angle of inclination. The reflected light that has passed through the half mirror (4) is adjusted by the concave lens (7) to generate astigmatism, and then is applied to the photodetector (8). Therefore, by performing the arithmetic processing of the output of each sensor (not shown) constituting the photodetector (8), it is possible to detect the focus shift to the signal surface of the light beam and the tracking shift to the signal track of the light beam. Therefore, by driving the objective lens (6) according to the detected output, the light beam can be correctly focused on the signal track of the disc.

(C) Problems to be solved by the invention In the above-mentioned device, the light beam generated from the laser diode (1) is not completely reflected on the surface of the half mirror (4), and the light amount is about half of the light amount. Is transparent. This is also the case with the half prism. The transmitted light is reflected by the wall surface (9) which is the facing surface of the laser diode (1) through the half mirror (4) of the base on which the optical component is mounted. The reflected light passes through the half mirror (4) again and returns to the laser diode (1), or the half mirror (4)
The photodetector is reflected by the laser beam and travels toward the photodetector (8). For example, as shown in JP-A-61-9845, a photodetector for reproducing the data signal recorded on the disk and for driving the objective lens (6). It is known that mutual interference with the necessary information light emitted to (8) and interference noise superposed on the information light have an adverse effect. The optical pickup device disclosed in JP-A-61-9845 discloses a surface of a half prism or a polarization beam splitter that is not used as an incident surface or an emission surface of a light beam in order to eliminate the adverse effect of the interference noise.
Since the unnecessary diffused light is suppressed as the diffuse reflection surface and / or the light absorption surface, the technique disclosed in the above publication is not applicable to the optical pickup device using the half mirror (4) as shown in FIG. It was not available. Further, processing the surface of the half prism or the polarization beam splitter is accompanied by an increase in the number of working steps, and it is not easy to process the half prism and the polarization beam splitter.

The present invention is to provide an optical pickup device made in view of the above points.

(D) Means for Solving Problems The present invention is directed to a light source arranged so that a light beam applied to a signal recording medium is projected from a reflection direction of a half mirror or a half prism, and the half mirror of the base. Alternatively, a mounting hole is formed in the facing surface of the light source through a half prism, and the mounting hole for mounting the half mirror or the half prism is closed, and the facing surface of the light source is a diffuse reflection surface and / or It is characterized by comprising a light absorbing surface and a closing plate formed.

(E) Operation The present invention is an optical pickup device in which the light source is arranged so as to project from the reflection direction of the half mirror or the half prism, and the mounting hole for mounting the half mirror or the half prism is used as a base. A light diffuse reflection surface and / or a light absorption surface is formed in a portion which becomes the facing surface of the closing plate which closes the mounting hole while being provided on the facing surface of the light source through the half mirror or the half prism.
The light beam transmitted through the half mirror or the half prism and applied to the facing surface is irregularly reflected and / or absorbed to reduce interference noise.

(F) Embodiment FIG. 1 shows an embodiment of the present invention. (10) is a laser diode serving as a light source for generating a light beam (laser light), and (11) is the laser diode (10). Diffraction grating for diffracting generated light beam, (12) half mirror for splitting optical path and generating astigmatism, (13) parallel light beam reflected by the half mirror (12) A collimator lens for making light, (14) an objective lens, (15) a concave lens for adjusting astigmatism of reflected light from a disc (not shown) transmitted through the half mirror (12), (16) Reference numeral) is a photodetector for reading an information signal recorded on the disk and for detecting a focus shift and a tracking shift of the focus of the light beam to the signal track. The objective lens (14) is attached to a biaxial drive mechanism ( 17 ) for driving the objective lens (14) in the biaxial directions of the disk tracking direction and the light beam focusing direction. Further, the diffraction grating (11), half mirror (12), collimator lens (1
The concave lens (3) and the concave lens (15) are fixed to a base (18) made of aluminum die-cast and are arranged at predetermined positions. A substrate (19) to which the laser diode (10) is fixed and a substrate (20) to which the photodetector (16) is fixed are attached to the base (18), and the biaxial drive mechanism ( 17). ) Is installed.

By the way, the half mirror (12) is pressed from one surface by a leaf spring (21) arranged so as not to block the optical path of the light beam, and both ends of the other surface are the space ( 22 ) of the base (18). The thick wall portion ( 23 ) is abutted and fixed at a predetermined position, but the base (18) has a half mirror (as shown in the partial sectional view of FIG. 2). Mounting hole (24) for mounting 12) is formed. The attachment hole (24) is provided with a closing plate (25) after the half mirror (12) is attached.
Is closed by The closing plate (25) is attached to the mounting hole (2
Since it requires only the precision that 4) is closed, it is molded with a synthetic resin material (ABS) that is easy to create,
As shown in the figure, a diffuse reflection surface ( 26 ) having a pyramid-shaped protrusion (26a) is formed on one surface of the laser diode (10) facing the laser diode (10) via the half mirror (12). The closing plate (25) is formed of black, which has a high light absorption rate.

 Next, the operation will be described with reference to FIG.

The light beam generated from the laser diode (10) is diffracted by the diffraction grating (11) in the same manner as the conventional one, and is formed into three beams of a main beam and two sub beams, and then a half mirror (12). The light is reflected by the surface of the disk toward the disk. The light beam reflected by the half mirror (12) is collimated by a collimator lens (13) and then incident on an objective lens (14), which is converged by the objective lens (14) to produce a disc signal. The surface is illuminated. The light beam applied to the signal surface is reflected by the signal surface and returns to the half mirror (12) as reflected light via the objective lens (14) and the collimator lens (13). The reflected light returning to the half mirror (12) will be transmitted through the half mirror (12) in the future, and astigmatism will be generated. Then, the reflected light transmitted through the half mirror (12) is applied to the photodetector (16) via the concave lens (15). Therefore, the output signal obtained from each sensor of the photo detector (16) is arithmetically processed, and a control signal corresponding to the arithmetically processed output signal is wound around the lens holder (27) of the biaxial drive mechanism ( 17 ). Focusing coil (28) and tracking coil (2
The objective lens (14) is driven to a predetermined position by driving the lens holder (27) by flowing it to 9), and the light beam is focused on the signal track of the disc, so that the signal recorded on the disc is read. You can

By the way, the light beam from the reflection direction of the half mirror (12) projected from the laser diode (10) to the half mirror (12) through the diffraction grating (11) has about half of the light amount. Although the light is reflected by the surface of (1) and goes toward the disk, about half of the remaining amount of light passes through the half mirror (12) and is applied to the closing plate (25). Here, a portion of the blocking plate (25) that faces the laser diode (10) via the half mirror (12) is provided with a quadrangular pyramid-shaped projection (26a) on one surface, and a diffuse reflection surface ( 26 ), the light emitted to the blocking plate (25) is diffusely reflected by the irregular reflection surface ( 26 ). Since the closing plate (25) is made of a black synthetic resin material, the amount of light reflected by the closing plate (25) is also reduced. Therefore, the reflected light reflected by the blocking plate (25) deviates from the optical path of information light necessary for reproducing the data signal recorded on the disk and for driving the objective lens (14). .

In the embodiment, the quadrangular pyramid-shaped protrusions (26a) are formed on the blocking plate (25) in order to form the diffused reflection surface, but the invention is not limited to this, and the diffused reflection surface may be formed by various forms. It is possible. Although the half mirror is used as the optical component for dividing the optical path, the same effect can be obtained by using the half prism.

(G) Effect of the Invention As described above, in the optical pickup device according to the present invention, the mounting surface for mounting the half mirror or the half prism is the base, and the facing surface of the light source through the half mirror or the half prism. Since a light diffuse reflection surface and / or a light absorption surface is formed in a portion of the closing plate that is provided on the opposite side and closes the mounting hole, unnecessary stray light deviates from the optical path of the necessary information light. Therefore, it is only necessary to form the light diffuse reflection surface and the light absorption surface for reducing the interference noise on the closing plate, which has the advantage of reducing the interference noise, and the closing plate does not require high accuracy in the mounting position. Since the closing plate is made of synthetic resin material, the light diffuse reflection surface and / or the light absorption surface can be easily formed and the degree of freedom of the shape and color can be effectively formed. It has a point.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a partial sectional view for explaining the present invention, FIG. 3 is a plan view showing a closing plate, and FIG. 4 is a half mirror. It is a model diagram which shows the optical system of the optical pickup device which was used. Description of main drawing numbers (10) …… laser diode, (12) …… half mirror, (18) …… base, (24) …… mounting hole, (25) …… blocking plate, ( 26 )… … Diffuse reflection surface.

Continuation of the front page (72) Kozo Suzuki Kozo Suzuki, 180 Sakata, Oizumi-cho, Ora-gun, Gunma Toyo Sanyo Electric Co., Ltd. (56) Reference JP-A-59-171039 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. An optical pickup device comprising various optical components built into a base and optically reading a signal recorded on a signal recording medium by irradiating the signal recording medium with a light beam. Yes, one of the optical components
A half mirror or a half prism for splitting an optical path, a light source arranged so that a light beam applied to the signal recording medium is projected from a reflection direction of the half mirror or the half prism, and the half The closing plate is provided with a mounting hole for mounting the half mirror or the half prism, which is formed on a surface of the base facing the light source via a mirror or a half prism, and a closing plate for closing the mounting hole. Is composed of a synthetic resin material,
An optical pickup device characterized in that a light diffuse reflection surface and / or a light absorption surface are integrally formed on the blocking plate.