JPH01287832A - Optical information reproducing device - Google Patents

Abstract

PURPOSE:To save the space and to miniaturize and lighten a pickup for reproducing optical information by respectively photodetecting the light including information via a disk, and the direct light from a light source to show the light emitting quantity of the light source with two photodetectors formed on both surfaces of one photodetector body. CONSTITUTION:A first photodetector OD1 to photodetect a light influencing information reflected by a disk 27 and a second photodetector PD2 to directly photodetect a light beam from a light source and monitor it are formed at the different position of both surfaces of one photodetector body 23 and a shading part is formed on the rear surface of the first photodetector PD1. Consequently, the light beam to pass through a disk to come in the opposite direction by both surfaces of one photodetector body 23 and the light beam not to pass can be photodetected and the shading part interrupts the bad influence of the light beam made incident on from the rear surface of the first photodetector PD1. Thus, since two photodetectors are formed at one photodetector body, the device can be miniaturized and lightened in weight and the reduction of an output and the increase of noise are prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for reproducing information from an information recording medium on which information is optically recorded, such as an optical video disc, a compact disc, or an optical disc. The present invention relates to an optical information reproducing device for reading this information.

[Conventional technology]

The fourth configuration of a conventional optical information reproducing device of this type is
The semiconductor laser device shown in the figure is the one shown in FIG. 5, which will be explained below.

Reference numeral 1 denotes a semiconductor laser light source, and the laser light emitted from this is reflected on the surface of a half mirror 2 and enters an objective lens 3.

The objective lens 3 focuses the incident light and irradiates it onto the disk 4,
The light reflected from the disk 4 returns to the objective lens 3 and half mirror 2 through the same path.

The light reflected on the back surface of the half mirror 2 reaches the light receiving element 5, where it is photoelectrically converted and the information on the disk 4 is extracted as an electrical signal.

On the other hand, the semiconductor laser light source 1 also emits light from the opposite surface, and the light enters the monitor light receiving element 6 installed on the opposite surface of the half mirror 2, and the negative feedback circuit 7 is activated by the output from the semiconductor laser light source. 1 and keeps the output of the semiconductor laser light source 1 constant.

The semiconductor laser light source 1 is attached to a silicon substrate 10 of a heat sink 9 attached to a stem 8, and the light receiving element 6 is placed on the stem 1.

[Problem to be solved by the invention]

In a conventional optical information reproducing device, one stem 8
A semiconductor laser light source 1 and a light-receiving element 6 behind the semiconductor laser light source 1 are provided on the top thereof.

These require attachment parts such as a heat sink 9 and lead pins 11, which, together with the relative positions of the semiconductor laser light source 1 and the light receiving element 6, has the drawback of increasing the size of the device.

In order to solve the above-mentioned problems of conventional optical information reproducing devices, the present invention provides a first light receiving element for reading information on a disc, and a control for controlling the output of a light source to constantize the amount of light from the light source. By forming the second light-receiving element in one light-receiving element body, the number of parts can be reduced, the device can be made smaller and lighter, and the light rays from the light source can be incident on the first light-receiving element. The purpose is to prevent negative effects such as a decrease in output and an increase in noise.

[Means to solve the problem]

In order to achieve the above object, the optical information reproducing device of the present invention includes a first light receiving element that receives the light beam containing information reflected by the disk, and a first light receiving element that receives and monitors the light beam from the light source in a straight line. The second light receiving element and the second light receiving element are formed at different positions on both sides of one light receiving element body, and a light shielding part is formed on the back surface of the first light receiving element.

[For production]

In the optical information reproducing device formed as described above, the light beam emitted from the light source is focused through the objective lens and irradiates the disk, and by its reflection, the light beam containing information and the light beam from the light source are The light beam that is emitted and directly reaches the light receiving element body reaches the light receiving surface of the first light receiving element and the light receiving surface of the second light receiving element.

The light beam, which is photoelectrically converted by the first light-receiving element and contains information, is converted into an electrical signal by the second light-receiving element, and is output as a monitor signal for the amount of light emitted by the light source.

By forming the first light-receiving element and the second light-receiving element on both sides of one light-receiving element body, it becomes possible to receive light rays that come from opposite directions and that do not pass through the disk.

The first light-receiving element and the second light-receiving element are formed at different positions of one light-receiving element body, and a light shielding part provided on the back surface of the first light-receiving element allows light to enter from the back surface of the first light-receiving element. It is possible to prevent harmful effects such as a decrease in the output and an increase in noise by blocking the light rays that occur.

〔Example〕

Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

Reference numeral 21 denotes a semiconductor laser light source, and since the light rays emitted from its negative surface are diverging lights, a part of the light rays 22 is transmitted to the light receiving element body 23.
passes through the hole 24 and is reflected on the surface of the half mirror 25,
The light is focused by an objective lens 26 and illuminates a disk 27 .

By being reflected by this disk 27, the light beam 28 containing the signal recorded on the disk 27 returns along the same path and is reflected by the back surface of the half mirror 25.
The light reaches the first light receiving element PD+ having a signal reading pattern 29 formed on one surface of the light receiving element body 23.

On the other hand, a part of the light rays 30 from the above-mentioned surface of the semiconductor laser light source 21 reaches the second light receiving element PD2 formed on the other surface around the hole 24 of the light receiving element body 23.

In this light-receiving element body 23, the substrate silicon forms an N layer which is an N type region, and a P layer which is a P type head region is usually formed in two places by selective diffusion of boron.
The two layers are PN-junctioned via a depletion layer O, which is a junction neutral layer.

One of the two P layers becomes the first light receiving element PD+ having the signal reading pattern 29, and the P layer side becomes the light receiving surface, and the P layer formed around the hole 24 becomes the first light receiving element PD+ having the signal reading pattern 29.
The N-layer side becomes the light-receiving surface of the light-receiving element PD2.

In this light receiving element body 23, when light is absorbed in the silicon substrate, which is the N layer, the light energy excites electrons in the valence band, and the electrons become freely movable as photocarriers.
By using the N layer as a cathode and the P layer as an anode,
Can be taken out as a signal to an external circuit.

Since the light-receiving element body 23 is provided with a light shielding part 31 on the back side of the first light-receiving element PD, the light beam from the semiconductor laser light source 21 is directly directed to the back side of the first light-receiving element PD. There is no incident.

Therefore, only the light ray 28 from the disk 27 reflected by the half mirror 25 enters the first light receiving element PD1, and since the first light receiving element PD+ is formed in the signal reading pattern 29, the light beam 28 from the disk 27 is reflected by the photoelectric conversion. In addition to information, it is extracted as an electrical signal such as tracking information.

On the other hand, the light ray 30 from the semiconductor laser light source 21 that is incident on the second light receiving element PD2 is extracted as information on the amount of incident light, that is, the amount of light emitted, and is fed back to the semiconductor laser light source 21 by the negative feedback circuit to determine the amount of light emitted. It is something that becomes constant.

〔Effect of the invention〕

As described above, the present invention converts light rays from a light source into two light-receiving devices formed on both sides of a single light-receiving element body, as a light beam containing information that passes through a disk, and a direct light beam from the light source that indicates the amount of light emitted by the light source. Each element receives light.

Therefore, since only one light-receiving element is required, the number of parts is reduced, space can be saved, and the optical information reproducing pickup can be made smaller and lighter.

Since a light-shielding portion is formed on the back of the first light-receiving element that receives light rays containing information, direct light from the light source, reflected light from the vicinity, etc. do not enter, and such light rays This can prevent a decrease in output, an increase in noise, etc. due to a decrease in the sensitivity of the first light-receiving element due to the incidence of light.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a perspective view of this as seen from the half mirror side, Fig. 3 is a block diagram of a light receiving element body, and Fig. 4 is a block diagram of a conventional device. , FIG. 5 is a perspective view of the light source chip same as above. 21... Semiconductor laser light source, 22, 28.30...
Light beam, 23... Light receiving element body, 24... Hole, 25...
・No.1-fmirror, 26...objective lens, 27...
Disk, 29...Signal reading pattern, 31...
Light shielding part, PDl...first light receiving element, P layer 2...second light receiving element. Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] a light source that emits a light beam for reproducing information; an objective lens that focuses and irradiates the light beam from the light source onto a disk;
a first light receiving element that receives the light beam that has passed through the disk and photoelectrically converts it into an electric signal; and a first light receiving element that receives the light beam from the light source without passing through the disk and photoelectrically converts the amount of received light; a light-receiving element body having second light-receiving elements formed at different positions on both surfaces;
1. An optical information reproducing device comprising: a light shielding portion provided on the back surface of a light receiving element.