JPS63228423A - Optical information processor - Google Patents

Abstract

PURPOSE:To minimize the number of optical parts by using polarized separated film to a dividing optical element to divide a reflecting optical flux from an information medium into two semicircle light fluxes for detecting a reflecting light flux, dividing it for a focus dislocation detection, simultaneously, separating it into two polarized components and obtaining even a magneto-optical signal from the difference of the light strength of two polarized components. CONSTITUTION:A P-polarizing component to the polarizing separating surface of a dividing prism 50 transmits polarizing separating films 55, 56 and 57 and comes to be a circular light flux 65 focused to a point 70. The right side half of an optical axis out of S-polarizing components of a reflecting light 5 is reflected by the polarizing separating film 55, comes to be a semicircle light flux 66, reflected by whole reflecting surfaces 59 and 60 of a rectangular triangular prism 58 and further, reflected by the polarizing separating film 57. The left side half of the optical axis out of S polarizing components of the reflecting light 5 is reflected by the polarizing separating film 56, comes to be a semicircle light flux 67 and further, reflected by the polarizing separating film 55. When the dividing prism 50 and the rectangular triangular prism 58 are used, three light fluxes 65, 66 and 67 can be arranged in the same direction. Thus, one photodetector to receive these light fluxes may be sufficient.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information processing device, and in particular to an optical information processing device with an improved structure of an optical head, suitable for optical disk devices, optical card devices, etc. It relates to a processing device.

[Conventional technology]

In optical disk devices, optical card devices, and the like, a defocus detection system is required because rotation and movement of the information medium cause surface blur. Various defocus detection methods have been proposed in the past, and an example is Japanese Patent Application Laid-Open No. 60-5954.
As described in No. 5, after the reflected light beam from the information medium is separated from the light beam from the light source by a beam splitter, it is split into two semicircular light beams by a mirror, etc., and the focal point of each of the divided light beams is There is a method in which two split photodetectors are arranged, one in front and the other in rear. In this method, a defocus detection signal is obtained from a two-split photodetector by using the fact that the size of the semicircular light beam on the photodetector surface changes due to surface wobbling of the information medium. If only one of the defocus detection signals is used, the detection signal is asymmetrical with respect to the direction of surface wobbling of the information medium. Therefore, by adding both defocus detection signals, the defocus detection signals can be made symmetrical.

In this conventional optical head, by aligning the dividing direction in which the reflected light is divided into two parts with a mirror or the like to match the track direction of the information medium, a track deviation detection signal can be obtained from the difference signal of the amount of light received by each two-split photodetector. Obtainable. Furthermore, it is also possible to reproduce hole-type, phase-type, and phase-change type information bits from the sum signal of the amount of light received by each of the two-split photodetectors.

[Problem that the invention seeks to solve]

In the conventional optical head described above, which uses a mirror or the like to split the reflected light beam into two, consideration is given to detecting the rotation of the polarization direction of the reflected light from the information medium and reproducing information, as in a magneto-optical disk device. It had not been done. Therefore, a beam splitter for separating the light flux for magneto-optical signal detection, optical components and photodetectors for detecting magneto-optical signals are required, which increases the number of optical components in the entire optical head, making it expensive and larger in size. , there was a problem of increased weight.

An object of the present invention is to reduce the number of optical parts by performing not only hole-drilling type, phase type, and phase change type information signal reproduction but also magneto-optical signal reproduction using the same optical system that detects defocus and track deviation. The object of the present invention is to provide an optical head that is small in size, inexpensive, and lightweight.

[Means for solving problems]

The above purpose is to use a polarization separation film in the splitting optical element that splits the reflected light beam from the information medium into two semicircular light beams for defocus detection, and simultaneously splits the light beam into two semicircular beams for defocus detection.
separated into two polarized components.

This is achieved by also obtaining a magneto-optical signal from the difference in light intensity of the two polarized components.

[Effect]

The principle of detecting defocus and the principle of reproducing magneto-optical signals used in the present invention will be explained with reference to FIGS. 10 to 12. 10th
The figure is a configuration diagram of an optical head according to the present invention, in which a semiconductor laser 1
The laser beam emitted from the diaphragm is imaged as a minute spot on the magneto-optical disk 3 by the aperture lens 2. The X-axis direction is taken in the paper plane of FIG. 10, and the direction perpendicular to the paper plane is taken as the y-axis direction.

Assuming that the polarization direction of the semiconductor laser 1 is the X-axis direction, the magnetization direction of the unrecorded area of the magneto-optical disk 3, indicated by the arrow 21 in FIG. 12(a), is directed, for example, in the direction indicated by the arrow 22a. The polarization direction of the laser beam reflected from the recording area rotates in the direction shown by the arrow 21a in FIG. 12(a'). On the other hand, the magnetization direction of the domain where information is recorded is
It is reversed in the direction shown by arrow 22b, and the polarization of the disk reflected light is rotated in the direction shown by arrow 21b in FIG. 12(a). The reflected light flux from the magneto-optical disk 3 is separated from the light emitted from the semiconductor laser 1 by a beam splitter 4. If the half-wave plate 23 is placed in the separated light beam 5 and the azimuth angle from the X axis is 22.5 degrees, the half-wave plate 23
The polarization direction of the light transmitted through the 9th-order polarizing beam splitter 24a is rotated by 45 degrees as shown in 12K(b).
and 24b are inserted up to about half of the luminous flux 5, respectively. The polarized light separation films 25a and 25b transmit polarized light components in the X direction,
Reflects the polarized light component in the y direction. Therefore, when the focused spot moves from the unrecorded area to the recorded domain, the light intensity of the transmitted light beam 26 of the polarizing beam splitters 24a and 24b becomes the first
The amount of light decreases from arrow 21ax to arrow 21bx in FIG. 2(b), and the amount of light, which is the sum of the reflected light beam 27a by polarizing beam splitter 24a and the reflected light beam 27b by polarizing beam splitter 24b, increases from arrow 21ay to arrow 21by.

Therefore, the light quantity of the transmitted light beam 26 is received by the photodetector 28, the reflected light beams 27a and 27b are received by the photodetectors 29 and 30, respectively, and the sum of the outputs of the photodetectors 29 and 30 and the photodetector 2
The magneto-optical signal can be reproduced by taking the difference from the output of 8.

In addition, each of the photodetectors 29 and 30 has a light-receiving surface divided into two parts, and the focal points 31a and 3 of the reflected light beams 27a and 27b are divided into two parts.
One of the disks 1b is placed forward and the other is placed approximately equal distances apart from the rear. When the disk 3 is at the focal position, the shape of the light flux on the detection surfaces of the photodetectors 29 and 30 is as follows.
When the semicircles 32a and 32b of FIG. 11(b) have the same size and the isk 3 is shifted in the direction of the stop lens 2, the photodetector 29 as shown in FIG. 11(a)
The semicircular shape 32a on the surface is larger, and the photodetector 30
The semicircular shape 32b on the surface is smaller. On the other hand, if the disk 3 shifts away from the lens 2, as shown in Fig. 11(c).
), the semicircular shape 32b on the light detection surface 1130 is larger. Therefore, the outputs of the two divided light receiving sections 29' and 29' of the photodetector 29 are sent to the photodetector 3 by the differential circuit 33a.
The outputs of the two divided light receiving sections 30' and 30' of 0 are connected to a differential circuit 33.
By taking the image at b, defocus signals can be obtained. However, since the defocus detection signal obtained from the photodetector 29 or 30 is asymmetrical with respect to the direction of displacement of the disk 3, the defocus detection signal obtained from the photodetector 29 or 30 is asymmetrical with respect to the direction of displacement of the disk 3. A defocus detection signal can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a configuration diagram of an optical head of an optical disk device according to the present invention. 1 is a semiconductor laser, 2 is a focusing lens, 3 is a magneto-optical disk, 4 is a beam splitter, and 23 is a 1/2 wavelength plate, and since their functions have been described previously, their explanation will be omitted. The reflected light 5 from the magneto-optical disk 3 is divided into three light beams 6 by a dividing prism 50 and a right triangular prism 58.
It is divided into 5, 66 and 67. FIG. 2 is a diagram for explaining in detail the configuration of the divided prism 50 and the right triangular prism 58.
．． Parallel glass plate 52. Triangular prism 53. It consists of a triangular prism 54 and polarization separation films 55, 56 and 57.

After the prisms 51, 52, 53, and 54 are polished to predetermined dimensions, polarization separation films 55, 56, and 57 are deposited on the prisms 51, 53, and 54, respectively, and bonded with ultraviolet curing resin. Polarized light component in the plane of the paper of the reflected light 5 from the disk 3,
That is, the P-polarized light component with respect to the polarization separation surface of the splitting prism 50 passes through the polarization separation films 55, 56, and 57, and reaches the point 70.
The right half of the S-polarized light component of the reflected light 5 is reflected by the polarization separation film 55 and becomes a semicircular light flux 66, which is focused on the total reflection surfaces 59 and 60 of the right triangular prism 58. It is reflected by the polarization separation It1157
reflected. Also, among the S-polarized components of the reflected light 5 (i), the left half of the optical axis is reflected by the polarization separation film 56 to become a semicircular beam 67, and is further reflected by the polarization separation film 55.
Using the separation prism 50 and the right triangular prism 58,
Since the three light beams 65, 66, and 67 can be aligned in the same direction, only one photodetector is required to receive these light beams. A photodetector [I71 is placed at the point. FIG. 4 shows the light-receiving surface of the photodetector 71, in which a semicircular light beam 66 is received by divided light-receiving elements 71a and 71b arranged on the left side.

By receiving the semicircular light beam 67 with the divided light receiving elements 71d and 7ie arranged on the right side, a defocus detection signal is obtained according to the defocus detection principle described above. Further, a divided light receiving element 7 arranged at the center receives a circular light beam 65 of the P polarized light component.
1c, and the light receiving element 71 receives the S polarized light component.
a, 71b.

A magneto-optical signal can be reproduced from the difference between the sum of the outputs of 71d and 71θ and the output of the light receiving element 71. The drilling type, phase type, and phase change type bits can be reproduced from the sum of all output signals of the photodetector 71. If the track direction of the disk 3 is perpendicular to the plane of the paper in FIG. is obtained. On the other hand, the track direction of disk 3 is
If it is within the paper plane of the figure, a light receiving element 71 that receives the luminous flux 65
o is divided into two parts as shown by 71c' and 71c' in FIG. 5, and a track deviation detection signal is obtained from the difference signal between them. By moving the right triangular prism 58 in the vertical direction in FIG. 1, the interval between the semicircular light beams 66 and 67 on the surface of the photodetector 71 can be adjusted as desired. This is useful for loosening the machining precision of the optical parts and absorbing machining and assembly errors through adjustment.However, if this is not necessary, the one-segment prism 50 and the right triangular prism can be integrated, and the split prism 50 shown in FIG. Prism 61 may be used. The trapezoidal prism 62 in Figure 0 is a combination of the triangular prisms 51 and 58 in Figure 2, and the other parts are the same as in Figure 2. The beam splitter 4, the half-wave plate 23, and the splitting prisms 50 and 61 are integrated by adhesive.

Needless to say, assembly becomes easier, and instead of using the half-wave plate 23, the one-split prism, photodetector, etc. may be rotated by 45 degrees.

FIG. 6 shows another embodiment in which the present invention is applied to an optical disc drive of a magneto-optical disk device. Items denoted by the same numbers have the same functions, so a description thereof will be omitted. The splitting prism 80 splits the reflected light 5 from the magneto-optical disk 3 into three beams 65, 66, and 67. Polarization separation films 84 and 85 are deposited between the 0-th and 82-83 spaces, respectively.
It becomes 5. Of the S-polarized light component of the reflected light 5, the right half of the optical axis is reflected by the polarization separation film 85 and becomes a semicircular light beam 66, which is reflected by the total reflection surface 86. On the other hand, the left half of the S-polarized light component on the optical axis is reflected by the polarization separation film 84 and further reflected by the polarization separation film 85 to become a semicircular light beam 67. As in the first embodiment described above, when the splitting prism 80 is used, the three light beams 65, 66, and 67 can be aligned in the same direction, so that the light receiving elements 90a, 90b, and 90c as shown in FIG. All the signals can be obtained from one photodetector 90 having 90d and 90e, that is, the output of each light receiving element is Sa with respect to the splint.

Assuming Sb, Sc, Sd, and Ss, the defocus detection signal is (Sb-8c) + (Sd-8s), and the magneto-optical signal is S a - (S b + S c + S d + S
e) The six-open type, phase type, and phase change type pit reproduction signal is (Sa+Sb+Sc+Sd+Ss),
If the track direction is perpendicular to the paper surface, the track deviation detection signal is obtained as (Sb+5c)-(Sd+Se). On the other hand, if the track direction is within the plane of the paper, the light receiving element 9
0a is divided into two as shown in Figure 9, 90a' and 90a.
' is obtained from the difference between the output signals of '.

〔Effect of the invention〕

According to the present invention, not only information signal reproduction of the drilling type, phase type, and phase change type, but also magneto-optical signals can be reproduced by the same optical system that detects defocus and track deviation. All of the above signals can be obtained from one photodetector, and an optical head that is small, inexpensive, and lightweight can be obtained with a small number of optical parts.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing one embodiment of the present invention, Fig. 2, Fig. 3
4 and 5 are diagrams for explaining in detail the embodiment of FIG. 1, respectively. FIG. 6 is a configuration diagram showing another embodiment of the present invention, and FIGS. 7 and 8. and FIG. 9 are diagrams for explaining the embodiment of FIG. 6 in detail, and FIGS. 10, 11, and 12 are diagrams for explaining the present invention in detail. 1... Semiconductor laser, 2... Stop lens, 3...
... Magneto-optical disk, 4... Beam splitter, 23
...half wavelength plate, 50.80...dividing prism, 58...right triangular prism, 71.90...photodetector.

Claims (1)

[Scope of Claims] 1. A light source and an imaging optical means for forming an image of the light beam emitted from the light source onto the information medium surface, and a light source that converts at least a portion of the light beam reflected from the information medium from the light beam emitted from the light source. a separating means for separating, a dividing means for dividing the separated beam separated by the separating means, and two photodetectors arranged in front and behind a convergence point of the divided beam divided by the dividing means. an optical information processing device, characterized in that the dividing means has a polarization separation film. 2. The optical information processing device according to claim 1, wherein the dividing means has at least two substantially parallel polarization separation films. 3. The optical information processing device according to claim 2, wherein the dividing means has a total reflection surface substantially parallel to the polarization separation film. 4. In claim 3, the dividing means comprises:
An optical information processing device comprising: a prism having a polarization separation film substantially perpendicular to the polarization separation film; and a right-angle prism having the total reflection surface. 5. In claim 3 or 4, the above-mentioned 2.
An optical information processing device characterized by integrating two photodetectors. 6. In claim 5, the photodetector is 6.
An optical information processing device characterized by having a light receiving area divided into three or more parts.