JPH07169063A - Optical head - Google Patents

Abstract

PURPOSE:To obtain an optical head which can increase the utilization efficiency of-light and detect with high accuracy the emission light amount of a semiconductor laser and a positional signal in the tracking direction of an objective lens with a simple and low-priced constitution. CONSTITUTION:In the optical head which irradiates an optical recording medium 6 with a laser beam from a semiconductor laser 1 which is displaceable at least in the tracking direction, reflection parts 5a, 10b for reflecting a part of a laser beam from the semiconductor laser 1 is provided in the objective lens 5 and its lens holder 10. There is provided in a light path between the semiconductor laser 1 and the objective lens 5 a semiconductor substrate 4 which has a mirror surface 4a for reflecting light from the semiconductor laser 1 and a light receiving part 4b having a light receiving area which is split into at least two parts in the tracking direction so as to receive reflected light from the reflection parts 5a, 10b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is designed to detect an optical head for recording and reproducing information on an optical recording medium, and particularly to detect a position signal in the tracking direction of an objective lens and the amount of light emitted from a semiconductor laser. It relates to an optical head.

[0002]

2. Description of the Related Art As a conventional optical head, for example, Japanese Patent Laid-Open No.
There is one disclosed in Japanese Patent Publication No. -206046. In this optical head, as shown in FIG. 9, the light emitted from the semiconductor laser 21 is reflected by the light receiving element 22, is irradiated onto the recording surface (not shown) of the optical disc through the objective lens 23, and the recording is performed. The reflected light that has undergone pit modulation on the surface is received by the light receiving element 22 via the objective lens 23.

As shown in FIG.
The detector 22a has two detectors 22a and 22b, and the detector 22a receives the reflected light on the recording surface of the optical disc, and detects the RF signal, the focus error signal, and the tracking error signal based on the output, and outputs from the semiconductor laser 21. The emitted light is detected by the detector 22b to detect the emitted light amount, and the emitted light amount of the semiconductor laser 21 is controlled based on the output.

[0004]

However, in the above-described conventional optical head, in the detecting section 22a of the light receiving element 22, a part of the light from the semiconductor laser 21 is reflected toward the objective lens 23 in the forward path, and the return path is returned. However, since the light modulated by the pits of the optical disk is received, the reflectance of the light receiving element 22 cannot be increased so much. For this reason, there is a problem that the light use efficiency is lowered, and the amount of light emitted from the semiconductor laser 21 cannot be detected with high accuracy in the detection unit 22b.

Further, in such an optical head, tracking control is performed by moving the entire optical head. Therefore, for example, when the position of the objective lens 23 in the tracking direction is optically detected, the semiconductor laser 21 is detected. It is necessary to provide another light source to configure the position detecting means. Therefore, there is a problem that the configuration becomes complicated and the cost becomes high.

The present invention has been made by paying attention to such conventional problems, and can effectively improve the light utilization efficiency, and can easily output the emitted light amount of the semiconductor laser and the position signal in the tracking direction of the objective lens. It is also an object of the present invention to provide an optical head which can be detected with high accuracy by an inexpensive structure.

[0007]

In order to achieve the above object, according to the present invention, an optical head is adapted to irradiate an optical recording medium with laser light from a semiconductor laser through at least an objective lens which can be displaced in the tracking direction. At
In the objective lens or a lens holder holding this,
A reflecting portion for reflecting a part of the laser light from the semiconductor laser is provided, and a mirror surface for reflecting the light from the semiconductor laser in the optical path between the semiconductor laser and the objective lens, and a reflection from the reflecting portion. A semiconductor substrate having a light receiving portion having at least two light receiving regions in the tracking direction is provided so as to receive light.

[0008]

In this structure, the laser light from the semiconductor laser is reflected by the mirror surface of the semiconductor substrate and then radiated to the optical recording medium through the objective lens, and a part of the laser light is transmitted to the objective lens or its lens holder. The light is reflected by the reflection portion provided and is incident on the light receiving portion of the semiconductor substrate having the light receiving region divided into at least two in the tracking direction.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. In this embodiment, the laser light emitted from the semiconductor laser 1 is converted into parallel light by the collimator lens 2 and then incident on the beam splitter 3, and the laser light transmitted through the beam splitter 3 is reflected on the semiconductor substrate 4. After that, the optical disc 6 is irradiated as a spot through the objective lens 5 which can be displaced in the tracking direction shown by the arrow.
The reflected light (return light) from the optical disk 6 is reflected by the semiconductor substrate 4 through the objective lens 5 and then incident on the beam splitter 3, and the return light from the optical disk 6 reflected by the beam splitter 3 is reflected. As shown in FIG. 2 as viewed from the direction of arrow A in FIG. 1, the light is received by a photodetector 9 through a condenser lens 7 and a cylindrical lens 8, and a known method is performed based on the output of the photodetector 9. Thus, the RF signal and the focus error signal and tracking error signal necessary for servo processing are obtained.

As shown in FIG. 3 as viewed from the direction of arrow B in FIG. 3, the semiconductor substrate 4 has a mirror portion 4a and a light receiving portion having two light receiving regions divided in two in the tracking direction of the objective lens 5. 4b and. In addition, as shown in FIG. 4 as viewed from the direction of arrow C in FIG.
The reflection portion 5a is provided on a part of the outer peripheral surface of the reflection portion 5a.
Is provided in a part of the lens holder 10 that holds the objective lens 5 and is exposed from the notch 10a.

In this way, in the mirror portion 4a of the semiconductor substrate 4, the laser beam transmitted through the beam splitter 3 is reflected to the objective lens 5 side in the outward path, and returned from the optical disk 6 which enters through the objective lens 5 in the return path. The light is reflected to the beam splitter 3 side. Further, in the reflecting portion 5a of the objective lens 5, a part of the laser light is reflected to the semiconductor substrate 4 side in the outward path, and the reflected light is received by the light receiving portion 4b of the semiconductor substrate 4. The outputs of the two light receiving regions of the light receiving unit 4b are supplied to the differential amplifier 11 and the adder 12, respectively, and the position of the objective lens 5 in the tracking direction is detected based on the output of the differential amplifier 11, and the adder is also added. The amount of emitted light of the semiconductor laser 1 is detected by 12, and the amount of emitted light of the semiconductor laser 1 is controlled based on the detected amount.

According to this embodiment, the mirror portion 4a of the semiconductor substrate 4 only reflects the laser beam on both the forward and backward paths and does not receive light for signal detection. Therefore, the reflectance of this portion should be increased. You can Therefore, since the light utilization efficiency can be improved, the mirror portion 4a
Also, a sufficient amount of light can be obtained as the laser light that is sequentially reflected by the reflecting portion 5a of the objective lens 5 and is incident on the light receiving portion 4b, whereby the position of the objective lens 5 in the tracking direction and the emitted light amount of the semiconductor laser 1 can be obtained. It can be detected with high accuracy.

Further, in the conventional optical head, in the detecting portion of the light receiving element, the light from the semiconductor laser is reflected toward the objective lens on the outward path, and the light subjected to the pit modulation of the optical disk is received on the return path. Because
There is a problem that the RF signal, the focus error signal, and the tracking error signal cannot be accurately detected due to the interference of the laser light on the forward path and the return path. However, in this embodiment, the photodetector that receives only the laser light on the backward path is used. Since these signals are detected based on the output of 9,
The laser light does not interfere with the outward path. Therefore, the RF signal, the focus error signal, and the tracking error signal can be detected more accurately in combination with the effect that the utilization efficiency of light can be improved.

FIG. 5 shows an essential part of the second embodiment of the present invention and is a view as seen from the direction of arrow B in FIG. In this embodiment, instead of providing the reflecting portion 5a for reflecting a part of the laser light on the objective lens 5, a part of the lens holder 10 is shown as shown in FIG. A reflecting portion 10b is provided on the light receiving portion 4b of the semiconductor substrate 4, and the light reflected by the reflecting portion 10b is incident on the light receiving portion 4b of the semiconductor substrate 4.
Other configurations are similar to those of the first embodiment.

According to this embodiment, the reflecting portion 10b can be formed more easily and with a high reflectance as compared with the case where the reflecting portion 10b is provided on the objective lens 5, so that the amount of light incident on the light receiving portion 4b is increased. Therefore, the position of the objective lens 5 in the tracking direction and the amount of light emitted from the semiconductor laser 1 can be detected with higher accuracy.

FIG. 7 shows a third embodiment of the present invention. In this embodiment, in the first embodiment, a light receiving element 4c is provided on the semiconductor substrate 4 so as to be separated from the light receiving portion 4b so as to receive a part of the laser light in the outward path.
The position of the objective lens 5 in the tracking direction is detected via the differential amplifier 11 based on the outputs of the two light receiving regions b, and the amount of light emitted from the semiconductor laser 1 via the amplifier 13 based on the output of the light receiving element 4c. Is detected. The lens holder 10 is formed with an inclined portion 10c so that the reflected light here does not enter the light receiving element 4c, as shown in FIG. 8 as seen from the direction of arrow E in FIG.

According to this embodiment, on the semiconductor substrate 4,
A light receiving element 4c is provided for receiving a part of the laser beam on the outward path without being reflected by the objective lens 5 or the lens holder 10, and the semiconductor laser 1 is output based on the output of the light receiving element 4c.
Since the amount of emitted light is detected, even if the objective lens 5 largely moves in the tracking direction, the amount of laser light incident on the light receiving portion 4c does not change, and therefore the amount of emitted light can be detected with higher accuracy. You can

[0018]

As described above, according to the present invention, the laser light from the semiconductor laser is reflected by the mirror surface of the semiconductor substrate and irradiated onto the optical recording medium through the objective lens, and a part of the laser light is irradiated. Since the light is reflected by the reflecting portion provided on the objective lens or its lens holder and is made incident on the light receiving portion of the semiconductor substrate having at least two light receiving regions in the tracking direction, the reflectance of the mirror surface of the semiconductor substrate Can be raised. Therefore, since a sufficient amount of laser light can be obtained at the light receiving portion of the semiconductor substrate, the position of the objective lens in the tracking direction and the emitted light amount of the semiconductor laser can be detected with high accuracy based on the output of this light receiving portion. In addition, the structure can be simplified and the cost can be reduced as a whole.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram viewed from the direction of arrow A in FIG.

FIG. 3 is a view similarly seen from the direction of arrow B.

FIG. 4 is a view as seen from the direction of arrow C in FIG.

FIG. 5 is a diagram showing a second embodiment of the present invention.

6 is a view seen from the direction of arrow D in FIG.

FIG. 7 is a diagram showing a third embodiment of the present invention.

8 is a view seen from the direction of arrow E in FIG.

FIG. 9 is a diagram for explaining a conventional technique.

FIG. 10 is likewise a diagram for explaining a conventional technique.

[Explanation of symbols]

 1 semiconductor laser 2 collimator lens 3 beam splitter 4 semiconductor substrate 4a mirror part 4b light receiving part 4c light receiving element 5 objective lens 5a reflecting part 6 optical disk 7 focusing lens 8 cylindrical lens 9 photodetector 10 lens holder 10a notch part 10b reflecting part 10c Inclined part 11 Differential amplifier 12 Adder 13 Amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruhiko Takemura 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd.

Claims (2)

[Claims] 1. An optical head configured to irradiate an optical recording medium with laser light from a semiconductor laser through at least an objective lens that can be displaced in a tracking direction, wherein the objective lens or a lens holder holding the optical lens is provided with A reflecting portion for reflecting a part of the laser light from the semiconductor laser is provided, and a mirror surface for reflecting the light from the semiconductor laser in the optical path between the semiconductor laser and the objective lens, and reflected light from the reflecting portion. To receive
An optical head comprising: a semiconductor substrate having a light receiving portion having a light receiving region divided into at least two in the tracking direction. 2. The optical head according to claim 1, wherein the semiconductor substrate is provided with a light receiving element which is separated from the light receiving portion and receives a part of laser light from the semiconductor laser.