JPH0240580Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is a video disk, digital
The present invention relates to an optical pickup device used for recording and reproducing on audio disks and the like.

Generally, this kind of optical pickup device is usually constructed of an optical system using a semiconductor laser, a lens, a reflecting mirror, etc., and an optical pickup device as shown in FIG. 1 is known.

FIG. 1 is a schematic diagram showing the configuration of a conventional optical pickup device. In the figure, 1 is a semiconductor laser, 2 is a collimator lens, 3 is a polarizing beam splitter, 4 is a quarter wavelength plate, and 5 is a Galvanometer mirror, 6 an objective lens, 7 an objective lens barrel support, 8 a converging lens, 9 a 4-split optical sensor, 10
is a light shielding plate, 11 is a focus actuator,
12 is a tracking actuator, 13 is a disk which is a recording medium, and 14 is a disk drive motor.

Disk 13, which is a recording medium such as a video disk, digital audio disk, etc.
is rotated at a predetermined speed by a disk drive motor 14. The laser beam from the semiconductor laser 1 passes through a collimator lens 2, a polarizing beam splitter 3, and a quarter-wave plate 4, reaches a galvano mirror 5, is deflected by 90 degrees by the galvano mirror 5, and then passes through an objective lens 6. The information recording surface of the disk 13 is focused through. The reflected light from the information recording surface returns to the polarizing beam splitter 3 in the reverse order as described above, is deflected by 90 degrees by the beam splitter 3, and passes through the light shielding plate 10 and the converging lens 8 to the 4-split optical sensor 9. incident. The optical sensor 9 receives the reflected light from the information recording surface and outputs a focusing error signal, a tracking error signal, and a readout signal for information recorded on the disk 13.

The objective lens 6 causes the laser beam from the semiconductor laser 1 to follow the vertical vibrations of the disk 13 that occur as the disk 13 rotates.
The drive is controlled so as to focus on the information recording surface No. 3. That is, the focus actuator 11
is controlled via a servo drive system (not shown) using the focusing error signal, thereby driving and controlling the objective lens 6 in a direction perpendicular to the information recording surface of the disk 1. Similarly, the galvanometer mirror 5 is operated by the tracking actuator 12 based on the above-mentioned tracking error signal.
The drive is controlled in a direction of 45 degrees with respect to the information recording surface of the disk 13. As a result, the laser beam from the semiconductor laser 1 follows the deviation in the radial direction of the information track on the disk 13 caused by the eccentricity of the disk 13, and always accurately focuses the information on the information track on the disk 13. Track the track.

Since such a conventional optical pickup device uses a fixed or movable mirror 5 or a prism as a deflecting means below the objective lens 6, the height H of the optical pickup itself is large. This has the drawback of making it difficult not only to make the entire optical pickup device smaller and thinner, but also to make the disk recording/reproducing device itself thinner.

The purpose of the present invention is to eliminate the drawbacks of the prior art described above, and to easily improve the precision of the optical system.
Moreover, it is an object of the present invention to provide an optical pickup device that can be configured to be thin.

To achieve this objective, the present invention has a fixed ellipsoidal reflector that also performs a 90° polarization action in place of the objective lens, and a drive system to correct focusing errors, tracking errors, and jitter. It is characterized by the fact that the system is arranged horizontally.

Hereinafter, embodiments of the optical pickup device according to the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram of the optical pickup device according to the present invention, and FIGS. 2 a to 2 d are a side view, a perspective view, a front view, and an explanatory diagram of the laser beam system of the present invention, respectively. In FIG. 2, a semiconductor laser 1, a collimator lens 2, a polarizing beam splitter 3, a 1/4 wavelength plate 4, a converging lens 8, a 4-split optical sensor 9, a light shielding plate 10, and a disk 1 which is a recording medium.
3. The disk drive motor 14 is the same as that shown in FIG.
This is a two-dimensional actuator that drives 6.

The optical pickup device according to the present invention shown in FIG. 2 is different from the objective lens 6 and the galvanometer mirror 5 in the conventional optical pickup device shown in FIG.
Instead, an ellipsoidal reflecting mirror 15 is fixedly provided,
Concave lens 1 driven in two-dimensional direction to compensate for focusing errors and tracking errors
6.

A laser beam from a semiconductor laser 1 is collimated by a collimator lens 2 with a spread angle of 30 minutes or less, passes through a polarizing beam splitter 3 and a quarter-wave plate 4, is spread by a concave lens 16, and is sent to an ellipsoidal reflector 15. reach. The ellipsoidal reflecting mirror 15 deflects the laser beam from the concave lens 16 by 90 degrees and focuses it on the information recording surface of the disk 13.
The reflected light from the information recording surface of the disk 13 returns to the polarizing beam splitter 3 in the reverse order described above, is polarized by 90 degrees by the polarizing beam splitter 3, and is divided into four parts via the light shielding plate 10 and the converging lens 8. The light enters the optical sensor 9. The polarizing beam splitter 3 of the optical pickup device according to the present invention differs from that shown in FIG. 1 in that the polarizing beam splitter 3 of the optical pickup device according to the present invention deflects the reflected light by 90 degrees in a direction parallel to the information recording surface of the disk 13. As in the case of FIG. 1, the four-division optical sensor 9 outputs a focusing error signal, a tracking error signal, and a readout signal for information recorded on the disk 13.

The concave lens 16 generates a laser beam by a two-dimensional actuator 17 arranged around the concave lens 16 via a servo system (not shown) based on the focusing error signal and tracking error signal obtained from the four-split optical sensor 9. The drive is controlled in directions parallel to and perpendicular to. This results in
As in the case of the prior art optical pickup device shown in FIG. The information track is tracked while always focusing on the information track on the disk 13 accurately.

The horizontal arrows shown in Figures 2c and d indicate that the concave lens 16 is used to compensate for focusing errors.
indicates the direction in which the concave lens 16 is driven in order to compensate for the tracking error, and the upward and downward arrows and the symbol indicating the direction perpendicular to the plane of the paper indicate the direction in which the concave lens 16 is driven to compensate for the tracking error. In addition, Fig. 2 d is the same as Fig. 2 a to c.
Replace the elliptic spherical reflecting mirror 15 with an equivalent convex lens 15' that performs the same function as the reflecting mirror 15,
Laser beam from semiconductor laser 1 is directed to disk 1
This figure shows how the information is converged on the information recording surface of No. 3.

Next, it will be explained with reference to FIG. 3 that focusing errors and tracking errors can be compensated for by driving the concave lens 16 as described above.

FIG. 3a shows the information recording surface of the disk 13 and the equivalent convex lens 1 due to the vertical vibration of the disk 13.
5' shows the outer diameter of the incident laser beam and the optical path of its reflected light when the distance from g and h are the optical paths of the reflected light when the disk 13 is vertically shaken.

The concave lens 16 aligns the disk 1 along the incident laser beam e and parallel to the beam e as shown by the arrow.
3, and is controlled so that the reflected beam from the information recording surface of the disk 13 always returns in parallel to the incident beam e in the direction of the optical sensor, as shown at f. As a result, the incident laser beam e becomes
Equivalent convex lens 15', that is, ellipsoidal reflecting mirror 15
This ensures that the information recording surface of the disk 13 is always properly focused. That is, the focusing error can be corrected by the above-described operation.

FIG. 3b shows the optical path of the incident laser beam when the concave lens 16 is moved in a direction perpendicular to the incident laser beam, and j indicates the optical path of the center of the incident laser beam.

As shown in the figure, when the concave lens 16 is moved in a direction perpendicular to the incident laser beam, the incident laser beam is shifted from the central axis of the equivalent convex lens 15', that is, the ellipsoidal reflecting mirror 15, on the information recording surface of the disk 13. It will focus on a point. That is, by driving and controlling the concave lens 16 in the above-mentioned direction according to the eccentricity of the disk 13, the concave lens 16 can compensate for the tracking error.

As mentioned above, the optical pickup device according to the present invention fixes an ellipsoidal reflector that also serves as 90° polarization instead of the objective lens in the conventional optical pickup device, and uses it to compensate for focusing errors and tracking errors. Since a concave lens that can be driven in two-dimensional directions is arranged, it is easy to configure the device to be small and thin. In addition, a single concave lens is sufficient, and it is lighter than a conventional objective lens with 3 to 5 lenses, making it easier to design the drive system and reducing the overall cost of the optical system that makes up the optical pickup device. It is also easy to improve accuracy.

FIG. 4 shows another experimental example of the optical pickup device according to the present invention. In the figure, a semiconductor laser 1, a collimator lens 2, a polarizing beam splitter 3, a quarter wavelength plate 4, and a recording medium are The disk 13, disk drive motor 14, and ellipsoidal reflector 15 are the same as in FIG. 2, and 18 is a two-dimensional actuator that drives the collimator lens 2.

The optical pickup device shown in FIG. 4 differs from the optical pickup device shown in FIG. The difference is that it is configured to be driven by a two-dimensional actuator 18 disposed around the periphery, but the other configuration and operation are the same as in the case of FIG. 2. Such an optical pickup device is applicable only when the vertical vibration and eccentricity of the disk 13 are relatively small. The reason for this is that the generally used quarter-wave plate has a wavelength variation of about 2% (8000 Å ± 160 Å) and an extinction ratio of about 30% at a beam divergence angle of 30 minutes, and the beam divergence angle is larger than this. This is because it is difficult to obtain a large extinction ratio, and therefore it is difficult to expand the dynamic range of the servo system for compensating for focusing errors and tracking errors.

Since the optical pickup device according to the present invention can be configured to be thin and compact, it can be effectively used not only as a recording and reproducing device for video disks and digital audio disks, but also as a disk device for optical information files for computers. be. In addition,
In the above description of the present invention, we did not discuss jitter control during video disc playback;
In the present invention, jitter control can be performed simultaneously by driving and controlling the concave lens 16 or the collimator lens 2 in three-dimensional directions.

As explained above, according to the present invention, it is possible to reduce the weight of the movable parts for compensating focusing errors and tracking errors, thereby making it possible to sufficiently improve the characteristics of the optical system. A small optical pickup device can be provided.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an optical pickup device according to the prior art, Fig. 2 a, b, c, and d are block diagrams of an optical pick-up device according to the present invention, and Fig. 3 a, b are focusing errors and tracking errors. FIG. 4 is a block diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Semiconductor laser, 2... Collimator lens, 3... Polarizing beam splitter, 4... 1/4 wavelength plate, 5... Galvano mirror, 6... Objective lens, 7... Objective lens barrel support, 8... Converging lens, 9... 4-split optical sensor, 10... Light shielding plate, 1
DESCRIPTION OF SYMBOLS 1... Focus actuator, 12... Tracking actuator, 13... Disk, 14... Disk drive motor, 15... Elliptical spherical reflector, 16... Concave lens, 17, 18...
...Two-dimensional actuator.

Claims (1)

[Scope of utility model registration request] By focusing the laser beam on the recording surface of the information recording disk and detecting the reflected light,
In an optical pickup device that obtains a focusing error signal, a tracking error signal, and an information detection signal, a laser beam is focused on the recording surface of an information recording disk and fixedly arranged so that the laser beam can be deflected by 90 degrees. a semiconductor laser for generating a laser beam, and an ellipsoidal reflector disposed between the elliptic spherical reflector and the semiconductor laser, and an ellipsoidal reflector disposed between the elliptic spherical reflector and the semiconductor laser in at least two dimensions to compensate for focusing errors and tracking errors. What is claimed is: 1. An optical pickup device comprising: a lens system movably disposed on the periphery of the optical pickup device;