JPH02103743A - Optical information processor - Google Patents

Abstract

PURPOSE:To dissolve a decrease of the quantity of return light to a detection system and deterioration of a magneto-optical signal due to the occurrence of a phase difference of light by equipping an access mechanism with an optical prism for dissolving a phase shift of light caused by rotating an arm. CONSTITUTION:The information processor is provided with the optical prism for dissolving the phase shift of light caused by rotating the arm, e.g. a columnar prism 50 having both reflecting surfaces of a light outgoing plane 52 rotated by 90 deg. against an incident plane 51. Consequently, it becomes an optical prism capable of making the incident light coming in the direction of (z) as shown in an arrow go out in the direction of (y), and since the incident plane 51 and the outgoing plane 52 are rotated around an optical axis by 90 deg., the direction of (p) and the direction of (s) are in the opposite relationship as seen from a fixed part S, and an advance or a delay in phase of the incident light and the outgoing light are canceled so that the phase difference becomes zero. By this method, the decrease of the quantity of return light to the detection system due to the occurrence of the phase difference and the deterioration of the magneto-optical signal can be dissolved.

Description

[Detailed Description of the Invention] [Summary] This invention relates to an improved structure of an optical information processing device that records and reproduces information using light. In an optical information processing apparatus having a swing arm type access mechanism for allowing a light beam to access a target track on a medium, the access mechanism is provided with an optical prism that eliminates a phase shift of light caused by rotation of the arm.

The optical prism is constituted by a columnar prism having both reflecting surfaces, the exit surface of which is rotated by 90' with respect to the light entrance surface.

[Industrial application field]

The present invention relates to an improved structure of an optical information processing device that records and reproduces information using light.

[Conventional technology]

In recent years, information processing devices require high-speed, large-capacity file memory as the amount of data increases, but optical information processing devices, so-called optical disc devices, have a lower recording capacity than magnetic disk devices. Although it is advantageous in terms of large capacity and medium portability, it has the disadvantage that access time is increased due to the weight of the moving parts.

Therefore, in optical disk devices, a device using a swing arm system as an access mechanism has been proposed as one method for shortening the access time.

FIGS. 4 and 5 show perspective views of essential parts of a conventional swing arm type access mechanism, with FIG. 4 showing the mechanism and FIG. 5 showing the optical system. To explain the mechanism with reference to FIG. 4, the disk medium 1 is rotated by a spindle motor 2, and the objective lens 3 is roughly accessed by a swing actuator 6 to a target track on the disk medium l. On the other hand, the light transmitted through the parallelogram prism 5 is focused into a beam spot with a diameter of about 1 μm by the objective lens, and the focus actuator 4 drives the objective lens 3 so that the beam spot is always irradiated onto the disk medium 1. ing. Note that 7 is a galvano mirror.

Next, to explain the optical system with reference to FIG. 5, the light emitted from the laser light source 11 is converted into perfectly circular parallel light by the collimator lens 10 and the perfectly circular correction prism 9, transmitted through the beam splitter 8, and then by the galvano mirror 7. The light enters the parallelogram prism 5. The galvano mirror 7 also serves to provide precise access of the light beam to the target track. In this optical system, the part up to the galvanometer mirror 7 is the fixed part S (the part surrounded by the broken line), and the part from the parallelogram prism 5 is the movable part V, and the weight of the movable part is small. The configuration is designed to shorten access time.

In addition, the other symbols 10 are collimator lenses, 11 are laser light sources, 12 are mirrors, 13 are condensing lenses, 14
．． 15 is a beam splinter, 16 is a cylindrical lens, 17 is a photodetector for detecting focus error, 1
Reference numeral 8 indicates a photodetector for detecting a tracking error, 19 indicates a polarizing beam splitter, and 20 indicates a photodetector for detecting Kerr rotation angle.
The portion from to the photodetector 20 is the disk medium 1.
This is a detection system that detects reflected signal light from the

[Problem to be solved by the invention]

By the way, in such a structure, the galvanometer mirror 7 and the parallelogram prism 5 interlock in the middle of the optical path, and the parallelogram prism 5 undergoes a rotational movement (indicated by an arrow). Otherwise, the light beam cannot precisely access the target track. However, if this happens, the following problem will occur, which will be explained with reference to FIG.

FIG. 6 is a diagram illustrating the conventional problem, and FIG. 6 fa) is a top view of a portion mainly consisting of the parallelogram prism 5.

The same symbols are attached to the same parts in FIGS. 4 and 5, but the parallelogram prism 5 can be placed in three positions by rotation, and the three positions A
, B, and C are illustrated. The linearly polarized light emitted from the laser light source 11 is passed through a collimator lens 10. Perfect circle correction prism 9. The incident linearly polarized light enters the parallelogram prism 5 from the galvanometer mirror 7 via the beam splitter 8, but when the parallelogram prism 5 is at position B, the incident linearly polarized light coincides with the p direction, and in that case, the p polarized light (in the p direction Since there is only light), no phase difference occurs.

However, when the parallelogram prism 5 is at position A or C, the incident linearly polarized light has a p-direction component and an s-direction component, and the reflective surface of the prism uses total internal reflection. , there is always a phase difference between the p-polarized light and the s-polarized light, and when the p-polarized light is incident on the reflective surface of the prism at an angle of 4°, the p-polarized light will lead the s-polarized light by 38°. Positions A and B in Figure 6
, C, the directions of the linearly polarized light incident from the fixed part S are shown. When a phase difference occurs, CDR
In OM and WORM type optical disk devices, the amount of light returning to the detection system decreases, and in magneto-optical optical disk devices, the quality of reproduced signals deteriorates.

Therefore, as mentioned above, in an optical disk device with a conventional swing arm type access mechanism, when the arm is rotated to access the disk medium, a phase difference occurs in the light and the light returns to the detection system. There are drawbacks such as a decrease in the amount of light and signal deterioration in the magneto-optical method.

The present invention proposes a swing arm type optical disk device that eliminates these drawbacks and provides an access mechanism that does not cause a phase difference in light even when the arm rotates. be.

[Failure to solve the problem]

The problem is to create an optical prism that eliminates the phase shift of light caused by the rotation of the arm. For example, as shown in the principle diagram shown in FIG.
This problem is solved by an optical information processing device equipped with a columnar prism 50 having both rotated reflective surfaces. In Fig. 1, Fig. 1 (al is a perspective view, Fig. 1 (b) is a top view and a plan view (the line with an arrow in these figures is an optical path), Fig. 1 F
C+ is a diagram showing the relationship between the incident linearly polarized light and the p-s direction on the entrance/exit surface.

[For production]

That is, the present invention uses, instead of the conventional parallelogram prism,
For example, a columnar prism 50 having two reflecting surfaces whose output surfaces are rotated by 90' with respect to the light incident surface is provided. Then, as shown in Figure 1 fal, incident light from two directions (
It is an optical prism that emits light (indicated by a line with an arrow) in the y direction, and the entrance surface and exit surface are at an angle of 90° with respect to the optical axis.
Due to rotation, the relationship between the p direction and the S direction as seen from the fixed part S (see Figure 5) is reversed as shown in Figure 1 (el), and the phase advance and delay of the incident light and the output light cancel each other out. and the phase difference becomes 0.

Therefore, it is possible to eliminate the decrease in the amount of light returned to the detection system and the deterioration of the magneto-optical signal due to the occurrence of phase difference.

〔Example〕

Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 2 is a diagram showing an example of an optical prism according to the present invention, where fal is a perspective view and FIG. 2 (bl is a top view). In the composite columnar prism 50P, the same parts in FIGS. 1 and 5 are given the same symbols, but with this configuration, light incident in the y direction can be emitted in the y direction, and the incident direction If the output directions are the same, it will be easier to incorporate an optical disk device having a conventional structure into an optical system.

Moreover, in the columnar prism 508, the phase of the incident light entering the entrance surface 51 and the output light exiting from the output surface 52 is advanced, the delay is canceled, and the phase difference becomes 0. Similarly, in the columnar prism 50A, the phase difference becomes 0. The phase difference becomes O, and no phase shift occurs.

FIG. 3 shows a perspective view of essential parts of an optical system according to an embodiment of the present invention incorporating such an optical prism, and the same symbols are attached to the same parts as those shown in FIG. 5. , the parallelogram prism shown in FIG.
The structure is simply replaced by P.

In this way, by easily replacing the prism,
Even when the arm rotates, no phase difference occurs in the light, which eliminates the reduction in the amount of light returned to the detection system and the deterioration of the magneto-optical signal.

Note that the optical prism according to the present invention is not limited to a columnar prism, and other prism shapes are also possible.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, the decrease in the amount of light returned to the detection system due to the generation of a phase difference in light and the deterioration of the magneto-optical signal are eliminated, and the swing arm type optical disk is designed to achieve high speed. This has a remarkable effect of improving the performance of the device.

[Brief explanation of the drawing]

1 fa) to (C) are principle diagrams; FIG. 2 is a diagram showing an example of an optical prism according to the present invention; FIG. 3 is a perspective view of essential parts of an optical system according to an embodiment of the present invention; 5 is a perspective view of the main part of the mechanical part of the swing arm type access mechanism, FIG. 5 is a perspective view of the main part of the optical system of the swing arm type access mechanism, and FIG. 6 is a diagram illustrating the problems of the conventional method. In the figure, S is a fixed part, ■ is a movable part, 1 is a disk medium, 2 is a spindle motor, 3 is an objective lens, 5 is a parallelogram prism, 4 is a focus actuator, 6 is a swing arm actuator, 7 is a galvano mirror 18 is a beam splitter, 9 is a circular correction prism, 10 is a collimator lens, 11 is a laser light source, 50, 508, 50B are columnar prisms, 50P is a compound columnar prism, 51 is an entrance surface, and 52 is an exit surface. There is.

Claims (2)

[Claims] (1) In an optical information processing device having a swing arm type access mechanism for allowing a light beam to access a target track on a disk medium, the access mechanism is made to eliminate the optical phase shift caused by the rotation of the arm. An optical information processing device characterized by comprising an optical prism. (2) The optical prism has an exit surface of 9 points relative to the light entrance surface.
2. The optical information processing device according to claim 1, comprising a columnar prism having both reflective surfaces rotated by 0°.