JPS60106039A - Optical information processor - Google Patents

Abstract

PURPOSE:To attain functions of both a glass coupling lens and a diffraction grating without using said coupling lens and with a price equivanent to said diffraction grating, by using a hologram for production of a tracking control beam. CONSTITUTION:The light beams of spherical waves are irradiated to a hologram 14 from a laser light source 2 to obtain three parallel beams L1-L3. Then different light spots are formed on the information track of a disk 1. Thus the tracking control is performed. The hologram of a dryplate can be naturally used and furthermore the reproduced holograms can be easily obtained with said hologram of the dryplate used as a master in a mass production mode. This can reduce greatly the cost compared with a conventional case.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to a device for optically controlling recording tracks of an optical information processing device such as a video tape or a PCM audio disc.

[Background of the invention]

In such a device, it is necessary to perform control so that the light beam for indulgence accurately follows the recording track. FIG. 1 shows a conventional example of such a control device.

This conventional example is shown in Japanese Patent Publication No. 53-13123. A spiral information track is recorded on the disk 1.

The light beam from the laser light source 2 passes through the coupling lens 3 and is supplied to the diffraction grating 4, where it is divided into three beams L1 to L3, reflected by the half mirror 5 and the total reflection mirror 6, and then reflected by the diaphragm lens 7 to the disc. It is projected onto the information surface of 1. As shown in FIG. 2, images are formed at different positions 81 to S3.

In other words, they are positioned with slight deviations from each other in the front and back of the information track 8 and in the perpendicular direction thereto.

When the center spot S□ is at the center of the track, the sub-spots 82. S3 irradiates a position shifted from the center to a different side. For this reason, the respective reflected lights are separately captured by photodetectors 10 and 11, and the difference between the electrical signals is detected by the control circuit 12, and by controlling the reflection mirror 6, the center spot S1 correctly follows the center of the information track 8. can do. Note that the reflected light from the center spot s1 is converted into an electrical signal by the photodetector 9 and supplied to the signal processing circuit 13.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive optical information processing device that can easily perform tracking control, which does not require a coupling lens or a diffraction grating as in the past.

[Summary of the invention]

The present invention is characterized in that a hologram is used to form a tracking control beam. Previously, the sword 0-link lens had to be precisely polished one by one because it was crow-like, and it was expensive and cost 1B.

According to the present invention, there is provided a tracking control device that is suitable for grand prize production and is advantageous for inexpensive optical information devices, which performs both functions without using a crow's coupling lens and at the same price as a diffraction grating. can do.

[Embodiments of the invention]

The present invention will be explained below with reference to the drawings. FIG. 3 shows an embodiment of the present invention. By irradiating the hologram 14 with a spherical wave light beam from the laser light source 2, the hologram 14 is divided into three parallel beams L1 to L3, and different light spots are imaged on the information track 8 of the TIF 1. Tracking control can be performed in the same way as the example explained in the figure. Next, a hologram, which is the gist of the present invention, will be explained using a manufacturing method shown in FIG. The present invention relates to what is generally called an off-Axis type hologram and an in-Axis type hologram.
By using both holograms of the eye type hologram, the curvature of the spherical wave from the beam source is converted by dividing the beam into a plurality of beams in different directions. For example, in the case where a spherical wave from a laser light source is converted into three parallel beams, a method for creating a hologram used at that time is shown in FIG.

First, a spherical wave beam is applied to the Ai dry plate 15 vertically as an object wave. Next, in order to create a central parallel beam by creating a system called an in-line hologram, the parallel reference wave beam J-beam A is pierced from the same direction as the beam A. Note that the half mirror 16 is used to combine beam A and beam Bi. Further, in order to create sub-beams necessary for tracking, the dry plate is irradiated with parallel reference wave beams C and D at a predetermined angle θ with respect to beam B. These reference wave beams C and D and the six beams A form an off-axis type hologram. Therefore, after creating a hologram image on the dry plate 15 in this manner, the developing unit 1 can create a hologram. For this hologram, the convergence point 1 of the object wave
If the laser light source is positioned at point 7, three parallel beams can be created as shown in FIG. Of course, you can use a dry plate hologram, but for mass production, you can easily create a duplicate hologram using this as a master. Therefore, it can be made much cheaper than the conventional method. In addition, when using a half-body laser, in order to protect the light emitting chip, we recommend using glass or sapphire of 0.1 to 0.
．． Since a plate of about 5 mm is attached, the NA of the coupling is
It is necessary to take this into account when e ) is large. In this case, a hologram may be created by inserting something similar to the protective plate into the optical path of the object wave beam A.

It is possible to realize a tracking control device that is suitable for inexpensive optical information processing equipment suitable for Tendo production and that performs both functions at the same price as a diffraction grating without having to do so.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a conventional optical information processing device, FIG. 2 is a diagram for explaining its operation, FIG. 3 is a diagram showing a configuration of an embodiment of the present invention, and FIG. FIG. 2 is a diagram for explaining a method for creating a hologram used in the present invention. 1...Tisf, 2...Laser light source, 5...Half mirror-16...Another mirror, 9,10.11...
・Photodetector, 12... Control circuit, 13... Signal processing circuit, 14 No. 1 Fig. No. 2 No. 2 (21 No. 3 Fig. 1/ Fig. 4)

Claims (1)

[Claims] In a mechanical device that uses an optical sporatra to read information recorded in tracks on a recording medium that optically records information, a light source and a diaphragm lens are used to image a spot of light from the light source on the recording medium. 1. An optical information processing device characterized by converting the curvature of a wavefront of a light source by installing a hologram between the two, and dividing a light beam after the wavefront conversion into a plurality of beams.