JPH0191327A - Optical head - Google Patents

Abstract

PURPOSE:To simplify the holding mechanism of a photodetection sensor by arranging a transparent parallel flat plate, intersecting an optical axis orthogonally, on an optical path connecting between a converging lens to converge reflection light from a disk surface and the photodetection sensor, and further, arranging a knife edge to shade a part of a light flux between the lens and a photodetection sensor. CONSTITUTION:An emitted beam from a semiconductor laser 1 is collimated 2, and is transmitted through a polarized beam slitter 3 and a lambda/4 plate 4, and is converged on the optical disk 6 by an objective lens 5. The beam reflected on the optical disk 6 is transmitted through the objective lens and the lambda/4 plate 4, and comes to be a linear polarized wave intersecting the emitted beam orthogonally, and is reflected by the polarized beam splitter 3. The light flux after being transmitted through the converging lens 7 is shaded partially by the knife edge 8, and further, the transparent parallel flat plate 10 is arranged on the optical path connecting between the converging lens 7 and the photodetection sensor 9 so as to intersect the optical axis orthogonally, and the light flux is transmitted through the transparent parallel flat plate 10, and is converged on the photodetection sensor 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical head for recording and reproducing information on an optical disk surface.

[Conventional technology]

Conventionally, in this type of optical head, as shown in FIG. The light is focused on the disk 6.

The beam reflected on the optical disk 6 passes through the objective lens 5 again.
It passes through the λ/4 plate 4, becomes a linearly polarized wave orthogonal to the output beam, and is reflected by the polarizing beam splitter 3.
The light beam after passing through the condensing lens 7 is partially blocked by the knife 8 and condensed onto the photodetection sensor 9 . The knife 8 is used as a focus detection means, and is usually called the knife method.

[Problem that the invention seeks to solve]

According to the conventional optical head described above, it is necessary to accurately arrange the light receiving surface of the light detection sensor 9 on the focal plane of the condensing lens 7, and in FIG. A mechanism for making fine adjustments in the B direction is required.

Furthermore, for detection by the Naifetsu method, C and D in the figure
It is necessary to perform precise fine adjustment of the sensor in the direction, the holding mechanism for the detection sensor 9 is complicated, and there are disadvantages in that positional deviation due to changes over time after adjustment is likely to occur.

An object of the present invention is to provide an optical head that solves the above problems.

[Means for solving problems]

The present invention provides an optical head for optically recording and reproducing information on an optical disk, etc., in which a transparent parallel plane plate is disposed orthogonally to the optical axis on an optical path connecting a lens that collects reflected light from a disk surface and a photodetection sensor. The optical head is characterized in that at least one lens is disposed, and a knife for blocking a part of the light beam is disposed between the lens and the photodetection sensor.

〔Example〕

Next, the present invention will be explained with reference to the following drawings.

In FIG. 1, which shows a cross-sectional view of an embodiment of the present invention, an emitted beam from a semiconductor laser 1 is collimated by a collimating lens 2, transmitted through a polarizing beam splitter 3 and a λ/4 plate 4, and then passed through an objective lens. 5, the light is focused onto an optical disk 6.

The beam reflected on the optical disk 6 passes through the objective lens 5 and the λ/4 plate 4 again, becomes a linearly polarized wave orthogonal to the output beam, and is reflected by the polarizing beam splitter 3. In the present invention, a part of the light beam after passing through the condenser lens 7 is blocked by a knife 8, and a transparent parallel plane plate 10 is installed on the optical path connecting the condenser lens 7 and the light detection sensor 9, perpendicular to the optical axis. The light beam is transmitted through a transparent plane-parallel plate 10 and condensed onto a photodetection sensor 9.

As shown in FIG.
After being refracted at θ2, the light ray 102 exits the plane-parallel plate lO and is focused at a focal point G on the optical axis.

In addition, when the parallel plane plate 10 does not exist, the light @101 transmitted through the condenser lens 7 travels on the broken line 103, and the distance between the two points F and G where the light is condensed under the focal point is Let it be X,
If d is the thickness of the parallel plane plate and n is its refractive index, then the distance The focal point position can be easily changed.

Two or more parallel plane plates may be used in combination.

〔Effect of the invention〕

According to the configuration of the present invention, the distance between the condenser lens and the photodetection sensor is kept constant, and the movement of the photodetection sensor only in directions C and D in FIG. Adjustment of the optical axis direction can be easily achieved by simply replacing the parts. therefore,
Since the holding mechanism for the photodetection sensor can be simplified and the number of component parts can be reduced, factors that cause deterioration over time can be reduced, and a stable optical head can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is a partial cross-sectional explanatory view of FIG. 1 of the present invention, and FIG. 3 is a cross-sectional view of a conventional example. 1... Semiconductor laser 2... Collimating lens 3... Polarizing beam splitter 4... λ/4 plate 5
...Objective lens 6...Optical disc 7...
・Condensing lens 8... Naifetsuji 9...
Photodetection sensor lO...parallel plane plate 2, 3

Claims (1)

[Claims] (1) In an optical head that optically records and reproduces information on an optical disk, etc., a transparent parallel plane plate is placed perpendicular to the optical axis on the optical path connecting the lens that collects reflected light from the disk surface and the photodetection sensor. What is claimed is: 1. An optical head characterized in that at least one of the above lenses is disposed, and a knife edge for blocking a part of the luminous flux is further disposed between the lens and the photodetection sensor.