JPH0827952B2 - Optical information reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention is 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.

[Conventional technology]

A conventional optical information reproducing apparatus of this type has a structure as shown in FIG. 7, and a semiconductor laser device used in this optical information reproducing apparatus is as shown in FIG. is there. These will be described below.

Reference numeral 1 denotes a semiconductor laser light source. Laser light emitted from the semiconductor laser light source is reflected by the surface of the half mirror 2 and is incident on the objective lens 3. The objective lens 3 focuses the incident light and irradiates the disc 4 with the light, and the light reflected from the disc 4 returns to the objective lens 3 and the 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, is photoelectrically converted by the light receiving element 5, and the information of the disk 4 is taken out as an electric signal.

On the other hand, the semiconductor laser light source 1 also emits light from the surface opposite to the above, and the light enters the monitor light receiving element 6 installed on the surface opposite to the half mirror 2, and the output thereof causes the negative feedback circuit 7 to output the semiconductor laser light source. Control the output of 1,
The output of the semiconductor laser light source 1 is kept constant.

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

[Problems to be Solved by the Invention]

In a conventional optical information reproducing apparatus, a semiconductor laser light source 1 and a light receiving element 6 to which a light beam is emitted from the semiconductor laser light source 1 are provided on one stem 8.

In addition, these require the heat sink 9 and the lead pins 11 as attachment parts, and there is a drawback that the apparatus becomes large in size in combination with the related position of the semiconductor laser light source 1 and the light receiving element 6.

In order to solve the above-mentioned problems of the conventional optical information reproducing apparatus, the present invention controls a first light receiving element for reading information on a disc and an output of the light source for making the light quantity of the light source constant. By forming the second light receiving element for this purpose in one light receiving element body, it is an object to reduce the number of parts and reduce the size and weight of the device.

[Means for solving the problem]

In order to achieve the above object, the optical information reproducing apparatus of the present invention is arranged on the optical axis of a light beam emitted from one side of a light source, and arranges a light receiving element body so as to block the light beam. In the light receiving element body, a light beam passage such as a hole or a slit for passing only the light near the center of the light rays emitted from the light source as the information reading light beam of the disc is formed, and the light source of the light receiving element body is formed. A first light receiving element for receiving the reflected light from the disk of the light near the center and reading the recorded information is formed on the facing surface and the reflecting surface, and the light beam on the side facing the light source is formed. A second light receiving element is formed around the passage for receiving the peripheral light of the light rays emitted from the light source and controlling the output of the light source.

Further, a mask is formed on the light receiving surface of the second light receiving element to determine a light receiving area where the light beam from the light source reaches the second light receiving element.

[Operation] In the optical information reproducing apparatus of the present invention configured as described above, the light near the center of the light rays emitted from the light source passes through the light ray passage formed in the light receiving element and the objective lens. Is focused on the recording surface of the disk and is focused. Then, the reflected light from the disc is received by the first light receiving element formed on the light receiving element body, photoelectrically converted into an electric signal, and taken out as a recording information signal.

On the other hand, the peripheral light of the light emitted from the light source is directly received by the second light receiving element formed around the light passage and is photoelectrically converted, and is taken out as an electric signal indicating the light emission amount of the light source. . Therefore, if the light source is feedback-controlled using this electric signal, the amount of light emitted from the light source can be constantly controlled.

As described above, the light emitted from one side of the light source is received by using the first and second light receiving elements formed on the front and back surfaces of the light receiving element body, thereby reading the recorded information on the disc surface. Since the power control of the light source can be realized, the structure thereof is extremely simple as compared with the conventional optical information reproducing apparatus shown in FIGS. 7 and 8.

Further, when the light receiving area of the peripheral light incident on the second light receiving element is made constant by the mask provided on the light receiving surface of the second light receiving element, it is possible to eliminate variations in light receiving characteristics.
Accurate power control can be performed.

〔Example〕

Next, a first embodiment of the present invention will be described with reference to FIGS.

In the figure, 21 is a semiconductor laser light source, 23 is a half mirror, and 27 is a light receiving element body. The light-receiving element body 27 is arranged between the semiconductor laser light source 21 and the half mirror 23, is located on the optical axis connecting the semiconductor laser light source 21 and the half mirror 23, and is radiated from one surface of the semiconductor laser light source 21. A hole 30 is formed for taking out only the light near the center of the laser light radiated on the disk as a light beam 22 for reading the recorded information on the disc.

Light near the center for reading recorded information that has passed through the hole 30
22 is reflected upward on the surface of the half mirror 23,
It is focused by an objective lens (not shown) so as to focus on the disk surface (see FIG. 7). Then, the reflected light beam 26 from the disk surface passes through the same path again and is a half mirror.
It returns to the 23 position, is reflected by the back surface of the half mirror 23, and is irradiated onto a predetermined position of the light receiving element body 27.

As shown in the detailed structure of FIG. 2, the light-receiving element body 27 is entirely composed of an N-type silicon substrate. As shown in FIG. 2 (A), on this silicon substrate, a predetermined signal reading pattern 28 (for receiving the reflected light 26 from the disk surface is received at a position where the reflected light beam 26 from the disk surface strikes. A first light receiving element PD ₁ made of a P-type silicon layer having a four-divided pattern) is formed, and the periphery of the hole 30 on the side facing the semiconductor laser light source 21 is shown in FIG. As shown in B), the second light receiving element PD formed of a P-type silicon layer for receiving the peripheral light 29 around the central light 22 and using the change in the received light amount for the power control of the semiconductor laser light source 21. ₂ is formed.

In order to form the light receiving elements PD ₁ and PD ₂ on the light receiving element body 27, for example, a P layer serving as a P type region is formed on a silicon substrate by boron selective diffusion, and the P layer and the silicon substrate are formed. Through the depletion layer which is a neutral layer
PN junction should be used.

When the two light-receiving elements PD ₁ and PD _{2 with the} PN junction are exposed to light, the electrons in the valence band are excited and become free electrons.
By using the N layer as a cathode and the P layer as an anode,
The emitted light can be taken out as an electric signal to the outside. Therefore, the reflected light beam 26 from the disk surface is reflected by the first light receiving element PD.
_{When 1} is irradiated, the change in the light amount is converted into an electric signal, and the recorded information on the disk can be taken out as an electric signal to the outside.

Further, when the second light receiving element PD ₂ formed around the hole 30 is irradiated with the ambient light 29, the light amount of the peripheral light 29 is converted into an electric signal, and the change in the light emission amount of the semiconductor laser light source 21 is changed. It can be taken out as an electric signal shown. Therefore, by feeding back the electric signal extracted from the second light receiving element PD ₂ to the semiconductor laser light source 21 via a negative feedback circuit (not shown), the light emission amount of the semiconductor laser light source 21 is always controlled to be constant. be able to.

In FIG. 3, instead of the hole 30 of the light receiving element body 27, a slit 31 having one open end is shown. The operation is the same as that shown in FIG. 1 and FIG.
The description is omitted.

Further, FIGS. 4 to 6 show another embodiment,
A mask 32 having a desired opening shape such as a circular shape, which is located in the _second light receiving element PD ₂ portion around the hole 30 in the first embodiment.
Is formed, and the light receiving area for the second light receiving element PD ₂ formed around the hole 30 is made constant by the mask 32.

As the method of forming the mask 32, for example, it is formed by using metal vapor deposition, printing or the like as shown in FIG. 5, or the shape of the portion where the light receiving element PD ₂ is formed as shown in FIG. Various methods such as a concave surface can be adopted.

The second light receiving element PD formed around the hole 30 as described above
_If the light receiving area of ₂ is made constant by the mask 32, the upper limit of the amount of received light can be made constant, so that variations in the characteristics of the light receiving element can be reduced, and malfunction of the monitor signal processing amplifier can be prevented. Also, the adjustment of the negative feedback circuit can be made simpler.

In each of the above-described embodiments, the light-receiving element body 27 includes not only the light-receiving elements PD ₁ and PD ₂ but also a circuit for increasing or calculating the electric signal photoelectrically converted by the light-receiving element. It may be an OEIC or an OEIC provided with a negative feedback circuit for controlling the semiconductor laser light source 21.

〔The invention's effect〕

As described above, according to the present invention, the light beam emitted from one side of the light source is received by using the first and second light receiving elements formed on the front and back surfaces of the light receiving element body. Since it is possible to read the recorded information on the disc surface and control the power of the light source, its structure is much simpler than the conventional optical information reproducing device, the number of parts is reduced, and the mounting space is reduced. The size and weight of the device can be reduced.

Further, since the first and second light receiving elements are formed on the opposite surfaces of the light receiving element body, respectively, the light guiding by the mirror, the light guiding by the optical fiber, etc. are not required, and the light receiving elements can be viewed from the opposite directions. It is possible to simultaneously receive the incident reflected light from the disk and the light beam for power control from the light source.

In addition, since the passage of the light beam for reading the recorded information of the disc is formed directly on the light receiving element, it is possible to make the position of the light beam on the forward and return paths to the disc close to each other, and the area and thickness of the half mirror of the optical system Not only can you reduce the size,
By forming the second light receiving element for power control of the light source around the passage of this light beam, the light beam for power control can be directly received. Therefore, the light amount per unit area of the light beam irradiating the disc and the light beam reaching the second light receiving element are close to each other, and the incident angle to the second light receiving element is close to a right angle, so that the power control of the light source is further improved. Since it can be performed accurately and a large light receiving area can be obtained, a large output can be obtained as a power control signal of the light source.

Further, since the light receiving area of the light receiving element is made constant by the mask formed on the light receiving surface of the second light receiving element, the upper limit of the light receiving amount becomes constant, and the variation of the output due to the variation of the light receiving area is reduced, and the monitor signal is reduced. It is possible to prevent a malfunction of the processing amplifier and to simplify the adjustment of the negative feedback circuit.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part of an embodiment of the present invention, FIG. 2 is a perspective view of a light receiving element body, FIG. 3 is a perspective view of a light receiving element body in which holes are replaced by slits, and FIG. FIG. 5 is a perspective view of a light receiving element body of another embodiment of the invention, FIG. 5 is a perspective view of the light receiving element body of FIG. 5 in which the mask shape is changed, and FIG. FIG. 8 is a perspective view of a light source chip of the conventional device. 21 …… Semiconductor laser light source, 22 near center light, 26,29 ……
Ambient light, 23 …… Half mirror, 27 …… Light receiving element, 28…
… Signal reading pattern, 30 …… hole, 31 …… slit, 32
...... Mask, PD ₁ ...... First light receiving element, PD ₂ ...... Second light receiving element.

Claims (2)

[Claims] 1. A light-receiving element body is disposed on the optical axis of a light ray emitted from one side of a light source so as to block the light ray, and the light-receiving element body is provided with a light beam for reading information from a disk. A light beam passage such as a hole or a slit that allows only the light near the center of the light emitted from the light source to pass through is formed, and on the surface opposite to the light source side of the light receiving element body, near the center. A first light receiving element for receiving the reflected light of the light from the disc and reading the recorded information is formed, and a light beam emitted from the light source is provided around the light beam passage on the side facing the light source. An optical information reproducing apparatus, characterized in that a second light receiving element for receiving the ambient light of the light source and controlling the output of the light source is formed. 2. The light receiving surface of the second light receiving element is provided with a mask for determining a light receiving area where a light beam from the light source reaches the second light receiving element. Optical information reproducing device.