JPH06290477A - Optical pickup - Google Patents

Abstract

PURPOSE:To monitor and to control the transmitted light output of a semiconductor laser as the light source of an optical pickup used for an optical disk. CONSTITUTION:A first reflection surface 4 and a second reflection surface 6 opposed to each other and a converging grating lens 5 are integrally formed with a glass element 3. A reflection type hologram composed of at least three different regions of interference fringes is formed on the whole or a part of first reflection surface 4, a semiconductor laser 1, multi-sected photodetector 7 and a photodetector 10 are stuck to and fixed on the glass element 3 with a sealing resin 8 and an integrated optical pickup is composed. Consequently, by detecting a first order light beam of the reflection type hologram by means of the photodetector, the reflected light beam from the semiconductor laser is monitored and the output of the laser beam is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup used in an optical information recording apparatus for recording or reproducing information with a laser beam.

[0002]

2. Description of the Related Art In recent years, an optical recording / reproducing apparatus has been widely used for consumer use for reproducing video discs and compact discs, and for commercial use, it has become popular for recording / reproducing large-capacity data.

A conventional optical pickup will be described below with reference to the drawings. FIG. 5 shows the configuration of a conventional optical pickup. In FIG. 5, 1 is a semiconductor laser, 2 is a heat sink, and 3 is a glass element. 4 is the first reflecting surface,
A reflection hologram is formed on the entire surface or a part thereof. A grating lens 5 is formed on the same surface as the first reflecting surface. 6 is a second reflective film
Is a reflective surface, 7 is a multi-segment photodetector, and 8 is a sealing resin.
This is an integrated optical pickup in which the semiconductor laser 1 and the multi-segment photodetector 7 are bonded and fixed to the glass element 3 and the sealing resin 8 in a state where one end of the semiconductor laser 1 is fixed on the heat dissipation plate 2.

The operation of the optical pickup constructed by using the above members will be described with reference to FIG. Light emitted from the semiconductor laser 1 is incident on the first reflecting surface 4, is reflected as specular reflected light and zero-order diffraction light, and is then incident on the second reflecting surface 6. The light flux reflected by the second reflecting surface 6 is focused on the disk substrate 9 by the focusing action of the grating lens 5. The light flux focused on the disk substrate 9 picks up a recording signal and is reflected. The reflected light including the recording signal passes through the grating lens 5 again, is reflected by the second reflecting surface 6, and then is reflected by the first reflecting surface 6.
Is incident on the reflection surface 4 of. Here, the first-order diffracted light is imaged on the multi-segment photodetector 7 by the reflection hologram formed on the first reflection surface 4. Here, the reflection hologram is composed of at least two regions having different interference cycles and has a focus error detection function and a tracking error detection function. By the above operation, reproduction of the recording signal, detection of focus error and detection of tracking error are performed.

[0005]

However, in the above-mentioned conventional configuration, since the characteristics of the laser light source such as the output light from the semiconductor laser and the deterioration state of the semiconductor laser are not monitored, it is difficult to record and reproduce. Had a point.

The present invention solves such a problem, and provides an optical pickup capable of always ensuring a stable laser light output and checking its deterioration state by monitoring the amount of light emitted from a semiconductor laser. That is the purpose.

[0007]

To achieve this object, an optical pickup according to the present invention comprises a semiconductor laser, a condensing optical element for condensing light emitted from the semiconductor laser on a disk substrate, and a semiconductor laser. A first reflecting surface that reflects the light emitted from the semiconductor laser and a second reflecting surface that reflects the light beam from the first reflecting surface face each other between the condensing optical elements,
A reflection hologram formed on the entire surface or a part of the first reflection surface and a photodetector for detecting first-order diffracted light from the reflection hologram on the first reflection surface are provided. .

[0008]

According to this structure, the reflection hologram for immediately diffracting the light emitted from the semiconductor laser formed on the first reflecting surface of the two facing reflecting surfaces as first-order diffracted light,
The output of the emitted light from the semiconductor laser can be monitored by the photodetector that detects the first-order diffracted light, and an optical pickup that can always secure a stable laser light output and can confirm the deterioration state of the semiconductor laser can be realized. Become.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows the configuration of an optical pickup according to Embodiment 1 of the present invention. In FIG. 1, 1 is a semiconductor laser, 2 is a heat sink, and 3 is a glass element. 4 is the first
The reflection type hologram is formed on the whole or a part of the central portion and the portion other than the central portion of the reflective surface. Reference numeral 5 denotes a grating lens, which is formed on the same surface as the first reflecting surface 4. Reference numeral 6 is a second reflecting surface made of a reflecting film, 7 is a multi-divided photodetector, 10 is a monitoring photodetector for the output of light emitted from a semiconductor laser, and 8 is a sealing resin. With one end of the semiconductor laser 1 fixed on the heat sink 2,
This is an integrated optical pickup in which the semiconductor laser 1, the monitor photodetector 10, and the multi-segment photodetector 7 are bonded and fixed to the glass element 3 and a sealing resin 8.

FIG. 2 shows the structure of the first reflecting surface 4. First
The reflection surface 4 is circular, and a reflection hologram A11a that guides the first-order diffracted light to the monitor photodetector 10 is formed in the central portion having a radius of 1/3 of the radius. Since the first-order diffracted light from the reflective hologram A11a is generated by the light emitted from the semiconductor laser 1, the first reflected surface 4 and the second
The specularly reflected light component from the central portion, which causes the multiple reflections to be repeated on the reflection surface 6 of FIG. A reflective hologram B11b that allows the first-order diffracted light to reach the multi-split photodetector 7 is formed on the entire surface or a part of the central portion except the central portion.

FIG. 3 shows the structure of the second reflecting surface 6. Second
An entrance window 12a for the light emitted from the semiconductor laser 1, an exit window 12b for the multi-divided detector, and an exit window 12c for the photodetector for monitoring are provided on the reflection surface 6 of.

The operation of the optical pickup configured as described above will be described with reference to FIG. The light emitted from the semiconductor laser 1 spreads while spreading on the first reflection surface 4
Incident on. The incident light is a specular reflection light on the first reflection surface 4 and the central portion of the first reflection surface 4 so as to guide the 0th-order diffracted light and the 1st-order diffracted light from the reflection hologram to the photodetector 10 for monitoring. The reflected hologram A11a formed on the first side reflects it as first-order diffracted light. Of this reflected light, specular reflected light and zero-order diffracted light are incident on the second reflecting surface 6.
The light flux reflected by the second reflecting surface 6 is focused on the disk substrate 9 by the focusing action of the grating lens 5. The light flux focused on the disk substrate 9 picks up a recording signal and is reflected. The reflected light including the recording signal passes through the grating lens 5 again, and the second reflecting surface 6
After being reflected by, the light enters the first reflecting surface 4. Here, a reflection hologram B11b formed on the first reflection surface 4
The first-order diffracted light from is imaged on the multi-segment photodetector 7. Since the reflection hologram 11b is composed of at least two regions having different interference fringes, focus error detection and tracking error detection can be performed from the signal of the multi-segment photodetector 7. On the other hand, the first-order diffracted light from the reflection hologram 11a formed in the central portion on the first reflecting surface 4 is focused on the monitor photodetector 10. The output of the semiconductor laser 1 can be monitored by detecting the output of the photodetector 10, and the deterioration state of the semiconductor laser 1 can be confirmed. Further, the output from the photodetector 10 is the semiconductor laser 1
It is possible to obtain a stable laser light output by feeding back to the drive circuit and controlling the drive current.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. The structure of the optical pickup of the second embodiment is similar to that of the optical pickup of the first embodiment shown in FIG. FIG. 4 shows the structure of the first reflecting surface 4 of the optical pickup used in this embodiment. The first reflection surface 4 has a circular shape, and a central portion having a radius of 1/3 of the radius is shielded so that the light flux is not reflected. Photodetector for monitoring the next-time diffracted light on all or part of the surface except the central part 1
A reflection hologram A11a leading to 0 and a reflection hologram B11 for making the first-order diffracted light reach the multi-segment photodetector 7.
b is formed. Similar to the first embodiment, the first-order diffracted light from the reflection hologram A11a is focused on the monitor photodetector 10 and the output thereof is detected to detect the semiconductor laser 1
The output light output from the can be monitored and controlled.
By this control, the deterioration state of the semiconductor laser 1 can be confirmed and a stable laser light output can be obtained.

[0015]

As is apparent from the above description of the embodiments, according to the present invention, the light emitted from the semiconductor laser formed on the first reflecting surface of the two opposing reflecting surfaces is analyzed for the first time. A reflection hologram A that diffracts as light and a photodetector that detects the first-order diffracted light thereof are provided, and the output of the semiconductor laser is monitored by the output of the photodetector. With this configuration, it is possible to realize an optical pickup which can secure a stable laser light output and can monitor the deterioration state of the semiconductor laser.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of a first reflecting surface of the optical pickup according to the first embodiment of the present invention.

FIG. 3 is a plan view showing a configuration of a second reflecting surface of the optical pickup according to the first embodiment of the present invention.

FIG. 4 is a plan view showing a configuration of a first reflecting surface of an optical pickup according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a schematic configuration of a conventional optical pickup.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Heat sink 3 Glass element 4 First reflective surface 5 Grating lens 6 Second reflective surface 7 Multi-split photodetector 8 Sealing resin 9 Disk substrate 10 Photodetector 11a, 11b Reflective hologram 12a Incident window 12b , 12c exit window

Claims (1)

[Claims] 1. A laser generator for emitting a laser beam,
A condensing optical element that condenses the light emitted from the laser generator on a disk substrate, and a first reflecting surface that reflects the light emitted from the laser generator between the laser generator and the condensing optical element. A reflective hologram formed on the entire surface or a part of the first reflective surface, the second reflective surfaces reflecting the light flux from the first reflective surface facing each other; An optical pickup which comprises a light detection means for detecting the diffracted light from the reflection hologram on the reflection surface, and monitors and controls the laser light output of the laser generator by the output of the light detection means.