JPS592243A - Optical device - Google Patents

Abstract

PURPOSE:To obtain an optical device which has high optical effciency with a small number of component parts of an optical system and the facilitated control of the optical system, by unifying a lens which leads the light beam transmitted from a semiconductor laser onto a disk and a prism which extracts the reflected light to form one body. CONSTITUTION:The light beams transmitted from a semiconductor laser 1 become approximately parallel to each other through prisms 2 and 3 and the 1st lens 5 and are irradiated on a disk 8 in the form of a minute spot through the 2nd lens 6. The reflected beams are reflected again on the junction surface A of the prisms 2 and 3 and received by a photodetector 9 through a lens 4. The flat surface 5a of the lens 5 is cemented to a surface 3a of the prism 3 in a monolithic structure. This eliminates the vapor deposition of a reflection preventing film on the surface 3a (5a), and an optical loss is reduced. Furthermore the control is facilitated for an optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to the structure of a small, lightweight, and easily adjustable optical system suitable for use in semiconductor laser optical devices, particularly optical disk devices.

In recent years, the development of devices using semiconductor lasers in place of gas lasers has become active. Optical disk device is part 1
This is an example. An optical disk device is a device that uses an optical system to irradiate a light beam emitted from a semiconductor laser onto an information medium (disk), thereby reproducing information recorded on the disk or recording information on the disk. It is something.

FIG. 1 is a diagram showing the configuration of a conventional optical disk device.

In FIG. 1, a light beam emitted from a semiconductor laser 1 is guided to a first lens 5 via a prism 20. Here, the prism 20 is made up of three prisms 2, 3 and 4 as shown in the same figure, and the light beam incident from the semiconductor laser 1 side passes through the prisms 2 and 3 and then passes through the lens 5.
On the other hand, the light beam incident from the lens 5 side is reflected by the joint surface A of the prisms 2 and 3 and is integrally constructed so as to be directed toward the prism 4. The first lens 5
The light beam guided by the first lens 5 is made almost parallel to the second lens 5 supported by the voice coil 7.
A minute light spot is irradiated onto the disk 8 through the lens 6 . This light beam is reflected by the disk 8, and this reflected beam passes through the second lens 6, first lens 5, prisms 3 and 4, and is received by a photodetector 9.

At this time, if information has been recorded on the disk 8 (for example, by forming holes according to the information on the disk surface), the reflected beam will be intensity-modulated according to the information. , the above information is obtained as an output signal of the photodetector 9. Note that the voice coil 7 is connected to the second lens 6
This is a device that moves a small amount of light at high speed, and is provided depending on the purpose of optical spot control, that is, focus control or tracking control.

In the apparatus having the configuration shown in FIG. 1, the output from the photodetector must be sufficiently large in order to detect an information signal with a good S/N ratio. For this reason, each surface of the prism and lens, for example, the first surface 3a of the prism 3,
It is necessary to prevent the reflection of the light beam by applying a thin film to one surface 58 of the lens 5, etc., and to reduce the loss of the light beam due to the prism and the lens as much as possible. but,
In the conventional optical disk device shown in Fig. 1, each component part of the optical system, i.e., the prism and lens, is all separated, so the optical efficiency φ is low, and thin films are not deposited on the prism, lens, etc. There is a drawback that the cost is high due to the large number of times.

Furthermore, since the prism and lens are separated, it is difficult to adjust the optical axes of the prism and lens, and there are also drawbacks that the device as a whole becomes large due to the large number of parts.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned drawbacks, and an object of the present invention is to provide an optical device that has high light efficiency, has a small number of optical system parts, and can easily adjust the optical system.

[Summary of the invention]

In order to achieve this object, the present invention is characterized in that a lens for guiding the light beam emitted from the semiconductor laser to the disk and a prism for extracting the reflected light from the disk are integrated. shall be.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention, and parts that perform the same functions as in FIG. 1 are denoted by the same reference numerals. That is, in the figure, the light beam emitted from the semiconductor laser passes through the prism 2.3 and the first lens 5 to become substantially parallel, and the light beam passes through the second lens supported by the voice coil 7 (not shown). A minute light spot is irradiated onto the disk 8 by the lens 6 . The reflected beam from the optical disk 8 passes through the second lens 6, the first lens 5, and the prism 3, and is reflected by the cemented surface A of the prism 2.3.
The light passes through the lens 4 and is received by the photodetector 9. In this embodiment, the "th" lens 5 has an end surface 5a on the semiconductor laser side.
It is a plano-convex lens designed to have a flat surface, and its flat surface 5a is aligned with one surface 3a of the prism 3, forming an integral structure. By fitting the first lens 5 and the prism 3 together as in this embodiment, there is no need to deposit an antireflection film on the surface 5a of the lens 5 and the surface 3a of the prism 3, and the loss of light is eliminated. will also decrease. Furthermore, the optical system can be easily adjusted, is resistant to vibrations, and can be made small.

FIGS. 3(a) and 3(b) are diagrams showing main parts of another embodiment of the present invention. 30 shown in FIG. 3(a) is formed by integrating the first lens 5, prism 3, and lens 4 shown in FIG. 2 at the manufacturing stage, and is shown in FIG. 3 fb). 40, the first lens 5 and the prism 3 are integrally formed at the manufacturing stage. Such integration can be realized by conventionally known techniques such as resin molding using plastic. By integrally forming the first lens 5 and the prism 3 from the manufacturing stage as in this embodiment, the number of parts of the optical system can be greatly reduced.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize an optical device with high optical efficiency, a small number of optical system parts, and easy adjustment of the optical system.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of a conventional optical disk device, Fig. 2 is a diagram showing an embodiment of the present invention, and Figs. 3 (a) and (b).
FIG. 3 is a diagram showing main parts of another embodiment of the present invention. 1... Semiconductor laser, 2... Prism, 5, 6...
- Lens, 8... Disc, 9... Photodetector. 10 / figure θ +2 figure 3 figure

Claims (1)

[Claims] 1. A light source, a lens that guides the light beam emitted from the light source to an information medium, and a prism that is provided between the lens and the information medium and extracts the reflected beam from the information medium. An optical device comprising: a plano-convex lens having a flat portion disposed on the light source side as the lens; and the plano-convex lens and the prism are integrated. 2. The optical device according to claim 1, wherein the plano-convex lens and the prism are integrated by resin molding.