JPH087872B2 - Optical head device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention records information on an information recording surface of an optical disc by using a minute spot in which a laser beam from a laser light emitting element is narrowed, or erases recorded information. The present invention particularly relates to an optical head device among optical disk devices for reproduction.

2. Description of the Related Art An optical head device used in a conventional optical disk device is disclosed in, for example, Japanese Patent Laid-Open No. 62-97141.

The conventional optical head device will be described below with reference to FIG.

In FIG. 4, reference numeral 1 is a laser light emitting element that generates laser light, and light 2 emitted from the laser light emitting element 1 passes through a hologram element 3 and is focused by an objective lens 4. The focused laser light focuses on the information recording surface 6 of the optical disc 5. The laser light at the focal point 7 is reflected, passes through the objective lens 4, and is diffracted by the hologram element 3 to become diffracted lights 8 and 9. The diffracted lights 8 and 9 are respectively incident on the second photodetectors 10 and 11 which are divided into two. On the other hand, the afterglow 12 from the laser light emitting element 1 which is directed to the opposite side to the information recording surface is monitored by the first photodetector 13 and used for controlling the optical output of the laser light emitting element 1. Reference numeral 14 denotes a case, which generally houses the laser light emitting element 1 and the first photodetector 13.

The operation of the optical head device configured as described above will be described below.

First, it is necessary to control the position of the objective lens 4 so that the laser light from the laser light emitting element 1 focuses on the recording information surface 6 of the optical disc 5. This is called focus control, and the reflected light from the optical disk 4 is separated into diffracted lights 8 and 9 by the hologram element 3, and a focus error signal is generated from the difference signal.

The generation of the focus error signal will be described in detail with reference to FIG.

FIG. 5 shows changes in the light spots on the second photodetectors 10 and 11. The two divided areas of the second photodetector 10 are divided into 10A, 10
Indicated by B. Similarly, two divided areas of the second photodetector 11 are indicated by 11A and 11B. Although not shown, the area on the hologram element 3 is divided into two, and the second photodetector 10, 11 is divided into two areas.
The upper light spot becomes a semi-circle when defocused.

First, when the optical disk 5 and the objective lens 4 are too far apart, the light spot spreads in a semicircular shape on the photodetectors 10A and 11A. Conversely, if the optical disk 5 and the objective lens 4 come too close to each other, the light spot spreads in a semicircular shape on the photodetectors 10B and 11B.

Next, when the laser light is focused on the information recording surface 6 of the optical disc 5, the light spot is condensed small on the line of two divisions as shown in the central figure. From this, the outputs of the two divided areas of the second photodetectors 10 and 11 are set to 10A, 10B and 1
With 1A and 11B, the focus error signal FE can be obtained as FE = (10A + 11A) − (10B + 11B).

Next, the tracking error signal TE can be obtained as TE = (10A + 10B) − (11A + 11B) by the general push-pull method.

Further, the reproduced RF signal can be obtained as RF = 10A + 10B + 11A + 11B by summing the respective areas of the second photodetectors 10 and 11.

On the other hand, the output of the laser light of the laser light emitting element 1 largely changes due to temperature and changes with time, which affects the reliability of the optical disc device. Therefore, the back light 12 of the semiconductor laser 1 is monitored and controlled by the first photodetector 13 so as to keep the light output constant.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above configuration, the first photodetector is used.
Since 13 and the second photodetectors 10 and 11 are separate, there is a problem that it is difficult to downsize the optical head device. Further, there are problems that the assembly and adjustment of the optical head device becomes complicated, or it is difficult to reduce the cost.

In particular, using the hologram element 3, the second photodetector 10, 11
When the is integrated with the first photodetector 13 in the case 14, the space in the case is very limited due to the miniaturization,
The fact that the first photodetector 13 and the second photodetectors 10 and 11 are separate is a big problem.

In view of the above points, the present invention has an object to provide an optical head device that simplifies the assembly and adjustment of the optical head, reduces the cost, and enables downsizing.

Means for Solving the Problems To achieve the above object, the invention of claim 1 of the present application comprises a hologram element for generating diffracted light corresponding to a focus error or a tracking error from reflected light on an information recording surface, and a laser light emitting element. A first photodetector for monitoring a part of the laser beam of, and a second photodetector for detecting the diffracted light formed on the same semiconductor substrate as the semiconductor substrate forming the first photodetector. It is an optical head device provided with.

According to the second aspect of the present invention, the hologram element that generates diffracted light corresponding to the focus error or the tracking error from the reflected light on the information recording surface, and a part of the laser light traveling from the laser light emitting element toward the information recording surface are reflected. An optical component having a predetermined reflectance, a first photodetector that monitors the reflected light, and a semiconductor substrate that forms the first photodetector detect the diffracted light that is formed on the same semiconductor substrate. And an optical head device including a second photodetector.

Operation With the above-described configuration, the invention of claim 1 of the present application generates the diffracted light corresponding to the focus error or the tracking error from the reflected light of the information recording surface by using the hologram element. The first photodetector monitors a part of the laser light from the laser light emitting element, and the second photodetector is formed on the same semiconductor substrate as the semiconductor substrate forming the first photodetector. Diffracted light corresponding to the focus error or tracking error is detected.

According to the second aspect of the present invention, a hologram element is used to generate diffracted light corresponding to a focus error or a tracking error from the reflected light on the information recording surface. A part of the laser light traveling from the laser light emitting element toward the information recording surface is reflected by an optical component having a predetermined reflectance, and the reflected light is monitored by the first photodetector. A second photodetector is formed on the same semiconductor substrate that constitutes the first photodetector, and diffracted light corresponding to the focus error or tracking error is detected.

Embodiment 1 FIG. 1 shows an optical head device according to an embodiment of the invention of claim 1 of the present application. A description will be given mainly of the parts different from the conventional example of FIG. 4 described above.

20 is a photodetector integrated on the same semiconductor substrate,
It comprises a first photodetector 20c and second photodetectors 20a, 20b. The first photodetector 20c monitors the afterglow 12 from the laser emitting element 1. Each of the second photodetectors 20a and 20b is composed of a photodetector divided into two parts. Reference numeral 21 denotes a case, which accommodates the laser light emitting element 1 and an optical receiver 20 integrated therewith.

The operation of the optical head device configured as described above will be described below.

As for the focus error signal, the reflected light from the optical disk 5 is separated into the diffracted lights 8 and 9 by the hologram element 3, and the case 21
It is guided to the second optical receivers 20a and 20b which are divided into two and are obtained from the difference between the outputs. Specifically, as described in the above-mentioned conventional example (FIG. 6), the optical receiver 20a is divided into two,
A signal obtained by subtracting the inner sum signal from each outer sum signal of 20b becomes the focus error signal.

The tracking error signal can also be obtained by subtracting the sum signal of the second optical receiver 20b divided into two from the sum signal of the second optical receiver 20a divided into two, as in the prior art example.

The reproduced RF signal can be obtained from the sum of the outputs of the second photodetectors 20a and 20b.

In addition, the back light 12 of the laser light emitting device 1 receives the first light receiver 20.
It is monitored by c and controlled to keep the light output constant.

As described above, according to the present embodiment, the hologram element 3 that generates the diffracted light corresponding to the focus error or the tracking error from the reflected light of the information recording surface 6 and a part of the laser light from the laser light emitting element 1 are monitored. And a second photodetector 20a, 20b for detecting the diffracted light formed on the same semiconductor substrate as the semiconductor substrate that constitutes the first photodetector 20c. This makes it possible to integrate the first and second photodetectors, simplify the assembly and adjustment of the optical head device, reduce the cost, and downsize the optical head device.

Next, before explaining the embodiment of the invention of claim 2 of the present application,
Processing of the grounds of the laser light emitting element and the first and second light receivers will be described with reference to FIGS. 2 and 6.

 First, a conventional example will be described with reference to FIG.

In FIG. 6, LD represents a laser emitting element, PDm represents a first optical receiver for monitoring laser light, and PD1 to PD4 represent second optical receivers for detecting a focus error or a tracking error. Six grounds are provided for each of the light emitting / receiving elements in correspondence with the number of elements. When all the light emitting / receiving elements are housed in the case, the number of pins coming out of the case is 12 in simple terms. When miniaturizing the optical head device, it is desired that the number of pins coming out of the case be as small as possible.

 Therefore, FIG. 2 shows an embodiment of the present invention.

In FIG. 2, LD is a laser light emitting element, PDm is a first light receiver for monitoring laser light, and PD1 to PD4 are second light receivers for detecting focus error or tracking error. Since the grounds of the light emitting and receiving elements are common, the number of pins coming out of the case will be reduced from 12 in the conventional case to 7. Therefore, if the ground of the light emitting / receiving element is shared and only one pin is taken out from the case, the number of pins can be considerably reduced and the optical head device can be miniaturized.

FIG. 3 shows an optical head device according to an embodiment of the invention of claim 2 of the present application. Hereinafter, a description will be given mainly of a portion different from the embodiment of the invention of claim 1 of the present application.

30 is a photodetector integrated on the same semiconductor substrate,
It is composed of first photodetectors 30c and 30d and second photodetectors 30a and 30b. The first photodetectors 30c and 30d are laser light emitting elements 1
A part of the laser beam traveling from the side toward the information recording surface 6 is monitored. Each of the second photodetectors 30a and 30b is composed of a photodetector divided into two parts. Reference numerals 31 and 32 denote optical elements having a predetermined reflectance, which reflect a part of the laser light traveling from the laser light emitting element 1 toward the information recording surface 6. 33 and 34 are optical elements 31 and 32
The reflected light is reflected by the first photodetectors 30c and 30d, respectively. Reference numeral 21 denotes a case, which houses the laser light emitting element 1 and an optical receiver 30 integrated with the laser light emitting element 1.

The operation of the optical head device configured as described above will be described below.

As for the focus error signal, the reflected light from the optical disk 5 is separated into the diffracted lights 8 and 9 by the hologram element 3, and the case 21
It is led to the second optical receivers 30a and 30b which are divided into two and are obtained from the difference between the outputs. Specifically, the focus error signal is a signal obtained by subtracting the inner sum signal from the outer sum signal of each of the optical receivers 30a and 30b divided into two as described in FIG. 5 of the conventional example.

The tracking error signal can be obtained by subtracting the sum signal of the second optical receiver 30b divided into two from the sum signal of the second optical receiver 30a divided into two, as in the case of the conventional example.

The reproduced RF signal can be obtained by the sum of the outputs of the second photodetectors 30a and 30b.

In addition, a part of the laser light traveling from the laser light emitting element 1 toward the information recording surface 6 is reflected by the optical components 31, 32 and reflected light 33,
Has generated 34. The reflected light 33, 34 is generated by the first light receiver 30.
It is monitored by c and 34d, and the sum signal of the outputs is used to control the optical output of the laser light emitting element 1 to be constant.
Since the reflected lights 33, 34 are part of the light directed toward the information recording surface of the laser light emitting element 1, more accurate signals can be taken out than by monitoring the after light. Also a photo detector
By setting 30 closer to the information recording surface 6 than the laser emitting element 1, the size of the case 21 in the height direction can be further reduced.

As described above, according to the present embodiment, the hologram element 3 that generates the diffracted light corresponding to the focus error or the tracking error from the reflected light of the information recording surface, and the laser light traveling from the laser light emitting element 1 to the information recording surface 6 are used. Optical parts 31 and 32 for reflecting a part and a first for monitoring the reflected light
By providing the photodetectors 30c and 30d and the second photodetectors 30a and 30b that detect the diffracted light formed on the same substrate as the semiconductor substrate that constitutes the first photodetector, 1
And the second photodetector are integrated to further reduce the size of the optical head device, and at the same time, it is possible to accurately monitor the laser light from the laser light emitting element and stably control the optical output of the laser light emitting element. .

In the embodiment of the present invention, the focus error signal is detected by the knife edge method, but this may be spot size detection or astigmatism by changing the diffraction pattern of the hologram element.

Further, the second photodetector for detecting the focus error or the tracking error uses two divided into two, which is divided into 6 or 4 depending on the servo detection method.
It may be a combination of division and two divisions, or a combination of six divisions and two divisions.

Furthermore, in the present embodiment, the hologram element and the case of the light emitting / receiving element were not integrated, but it goes without saying that the present invention can be applied to an integrated hologram element and case.

As described above, according to the present invention, a hologram element that generates diffracted light corresponding to a focus error or a tracking error from reflected light on an information recording surface, and a part of laser light from a laser light emitting element are monitored. By providing a first photodetector for detecting the diffracted light and a second photodetector for detecting the diffracted light formed on the same substrate as the semiconductor substrate forming the first photodetector. By integrating the two photodetectors, the assembly and adjustment of the optical head device can be simplified, the cost can be reduced, and the optical head device can be miniaturized, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical head device in an embodiment of the present invention, FIG. 2 is a wiring diagram of a light emitting / receiving element in the present invention, and FIG.
FIG. 4 is a block diagram of an optical head device according to another embodiment of the present invention, FIG. 4 is a block diagram of a conventional optical head, and FIG. 5 is a view for explaining a change of an optical spot on a second optical receiver. FIG. 6 is a wiring diagram of a conventional light emitting / receiving element. 1 ... Laser light emitting element, 3 ... Hologram element, 4 ...
Objective lens, 5 ... Optical disc, 6 ... Information recording surface, 8,
9 …… Reflected light, 10,11 …… Second photodetector, 12 …… Backlight,
13 …… First photodetector, 14 …… Case, 20,30 …… Integrated photodetector, 31,32 …… Optical element.

Claims (4)

[Claims] 1. A laser beam from a laser light emitting element is incident on an information recording surface, and a laser beam generated by using a hologram element from reflected light on the information recording surface corresponds to a focus error or a tracking error with respect to the information recording surface. In the optical head that guides the diffracted light to the photodetector and reproduces or records information, a part of the laser light from the laser light emitting element is monitored.
And an at least two second photodetectors for detecting diffracted light corresponding to the focus error or the tracking error are formed on the same semiconductor substrate. 2. A laser beam from a laser light emitting element is incident on an information recording surface, and a laser beam generated by using a hologram element from a reflected light of the information recording surface corresponds to a focus error or a tracking error with respect to the information recording surface. In an optical head that guides the diffracted light to a photodetector and reproduces or records information, a part of the laser light traveling from the laser light emitting element to the information recording surface is reflected by an optical component having a predetermined reflectance, and the reflection is performed. A first photodetector for monitoring the reflected light and at least two second photodetectors for detecting the diffracted light corresponding to the focus error or the tracking error are formed on the same semiconductor substrate. Optical head device. 3. The optical head device according to claim 1, wherein the ground of the laser light emitting element, the ground of the first photodetector and the ground of the second photodetector are common. . 4. An optical head device according to claim 1, wherein the laser light emitting element, the first photodetector and the second photodetector are contained in one case.