JP2701654B2 - Optical pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for use 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, optical recording / reproducing apparatuses have been widely used for reproduction of video disks and compact disks for consumer use, and have been widely used for recording and reproducing large-capacity data for business use.

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

The operation of an optical pickup constructed using the above members will be described with reference to FIG. The light emitted from the semiconductor laser 1 is incident on the first reflecting surface 4, is reflected as specular reflected light and the 0th-order diffracted light, and then is incident on the second reflecting surface 6. The light beam reflected by the second reflection surface 6 is condensed on the disk substrate 9 by the light condensing action of the grating lens 5. The light beam focused on the disk base 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 reflection surface 6, and then is reflected by the first reflection surface.
Incident on the reflection surface 4. Here, the first-order diffracted light forms an image on the multi-split 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 periods, and has a focus error detection function and a tracking error detection function. With the above operations, the recording signal is reproduced, the focus error is detected, and the tracking error is detected.

[0005]

However, in the above-mentioned conventional configuration, the characteristics of the laser light source, such as the emission light output from the semiconductor laser and the state of deterioration of the semiconductor laser, are not monitored, so that the recording / reproducing becomes difficult. Had a point.

SUMMARY OF THE INVENTION The present invention solves such a problem, and provides an optical pickup capable of constantly stabilizing a laser light output and monitoring its deterioration state by monitoring the amount of light emitted from a semiconductor laser. The purpose is to do so.

[0007]

In order 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 for reflecting light emitted from the semiconductor laser between the condensing optical elements, and a second reflecting surface for reflecting a light beam from the first reflecting surface;
A reflection type hologram formed on the entire surface or a part of the first reflection surface, and a photodetector for detecting a first-order diffracted light from the reflection type hologram on the first reflection surface are provided. .

[0008]

According to this configuration, a reflection type hologram for diffracting the emitted light from the semiconductor laser formed on the first reflecting surface of the two opposing reflecting surfaces as first-order diffracted light immediately,
The output of the semiconductor laser can be monitored by the photodetector that detects the first-order scattered light, thereby realizing an optical pickup that can always maintain a stable laser light output and check the deterioration state of the semiconductor laser. Become.

[0009]

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 hologram is formed on the entire surface or a part other than the central portion and the central portion. Reference numeral 5 denotes a grating lens formed on the same plane as the first reflection surface 4. Reference numeral 6 denotes a second reflection surface made of a reflection film, reference numeral 7 denotes a multi-segment photodetector, reference numeral 10 denotes a photodetector for monitoring the output of the light emitted from the semiconductor laser, and reference numeral 8 denotes 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 monitoring photodetector 10, and the multi-segment photodetector 7 are bonded and fixed with a glass element 3 and a sealing resin 8.

FIG. 2 shows the structure of the first reflecting surface 4. First
The reflection hologram A11a that guides the first-order light to the monitor photodetector 10 is formed at a central portion having a radius of 1/3 of the radius. Since the first-order diffracted light from the reflection hologram A11a is generated by the emitted light from the semiconductor laser 1, the first reflection surface 4 and the second
Specularly reflected light components from the central portion where multiple reflections are repeated on the reflection surface 6 are shielded. A reflection hologram B11b is formed on the entire surface or a part other than the central portion to make the first-order diffracted light reach the multi-segmented photodetector 7.

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

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 and spreads on the first reflection surface 4.
Incident on. Incident light, the specular reflection light from the first reflecting surface 4, the first formed in the central portion of the reflecting surface 4 a reflection hologram A11a, in 0-order diffracted light and reflection type hologram A11a from B11b Diffracted, monitor photodetector 1
The light is reflected as first-order diffracted light guided to zero. Of the reflected light, the specular reflected light and the zero-order diffracted light are reflected by the second reflecting surface 6.
Incident on. The light beam reflected by the second reflection surface 6 is condensed on the disk substrate 9 by the light condensing action of the grating lens 5. Thus, the first reflection surface 4 is formed on the first reflection surface 4.
Reflection holograms A11a and B11b
The light that has not been diffracted is reflected by the first reflecting surface 4.
By irradiating the disc substrate 9 with the
This is preferable because the use efficiency of the compound can be improved. The light beam condensed 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 enters the first reflecting surface 4. Here, the first-order diffracted light from the reflection hologram B11b formed on the first reflection surface 4 forms an image on the multi-segmented photodetector 7. Since the reflection hologram B11b includes at least two regions having different interference fringes, it is possible to detect a focus error and a tracking error from the signal of the multi-segment photodetector 7.
On the other hand, the first-order diffracted light from the reflection type hologram A11a formed in the central portion on the first reflection surface 4 is focused on the monitoring photodetector 10. By detecting the output of the photodetector 10, the output of the emitted light from the semiconductor laser 1 can be monitored, and the state of deterioration of the semiconductor laser 1 can be confirmed. Furthermore, a stable laser output signal can be obtained by feeding back the output from the photodetector 10 to the drive circuit of the semiconductor laser 1 and controlling the drive current. As described above, according to the present invention, in an optical pickup in which light incident by at least two opposing reflecting means is reflected in a direction opposite to the direction of incident at least twice and guided to a recording medium, The distance from the semiconductor laser to the disk base is extremely reduced by guiding a part of the light incident on the disk base by the reflection hologram provided on all or a part of the reflection means to the photodetector. Can be. Further, since the width of the entire optical pickup can be reduced because the optical axis of the light guided to the disc substrate while being reflected by the reflection surface is substantially in a straight line, the advantage of the optical pickup of this type remains as it is. The output adjustment of the semiconductor laser in the optical pickup of this type, which was very difficult, can be realized with a simple configuration, and the deterioration state of the semiconductor laser can be monitored. Therefore, a highly reliable optical pickup having a very small size and stable laser light output can be realized. In addition, reflection type
Diffracted by reflection hologram of light incident on the program
The reflected light is reflected toward the monitor photodetector.
And it is no longer guided to the disc base,
The light reflected without being diffracted by the gram is reflected by the first reflecting surface.
Through the second reflecting surface and the condensing optical element together with the reflected light
And irradiates the disc substrate, improving light use efficiency.
Can be up.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. The configuration of the optical pickup of the second embodiment is the same as that of the optical pickup of the first embodiment shown in FIG. FIG. 4 shows the configuration of the first reflection surface 4 of the optical pickup used in this embodiment. The first reflecting surface 4 has a circular shape, and a central portion having a radius of 1/3 of the radius is shielded so that a light beam is not reflected. Monitor light detector 1 for first-order scattered light on the whole surface or a part other than the central part
0, and a reflection hologram B11 that causes the first-order diffracted light to reach the multi-segmented photodetector 7.
b is formed. As in the first embodiment, the first-order diffracted light from the reflection type hologram A11a is condensed on the monitoring photodetector 10 and the output thereof is detected, whereby the semiconductor laser 1 is detected.
The output of the light emitted from the light source 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 embodiment, according to the present invention, outgoing light from the semiconductor laser formed on the first one of the two opposing reflecting surfaces is converted into the first-order diffracted light. And a photodetector for detecting the first-order diffracted light is provided, and the output of the photodetector is used to monitor the output of the light emitted from the semiconductor laser. With this configuration, the distance from the semiconductor laser to the disk substrate can be extremely reduced. Further, since the optical axis of the light guided to the disc substrate while being reflected by the reflecting surface is substantially in a straight line, the width of the entire optical pickup can be reduced, and the advantage of this type of optical pickup is maintained, but the stability is maintained. It is possible to realize an optical pickup which can secure the output of the laser light and can monitor the deterioration state of the semiconductor laser. Light incident on the reflection hologram
Of the light diffracted by the reflection hologram
Is reflected toward the photodetector and is guided to the disk base
Is not diffracted by the reflection hologram,
The emitted light is combined with the light reflected by the first reflecting surface in the second
Irradiates the disc substrate through the reflective surface and the focusing optics
Therefore, the light use efficiency can be improved.

[Brief description of the drawings]

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

FIG. 2 is a plan view illustrating a configuration of a first reflection 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 reflection 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 reflection 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 reflection surface 5 Grating lens 6 Second reflection surface 7 Multi-segmented photodetector 8 Sealing resin 9 Disk base 10 Photodetector 11a, 11b Reflection hologram 12a Incident window 12b , 12c Injection window

Claims (1)

(57) [Claims] 1. A laser generator for emitting a laser beam, a converging optical element for condensing light emitted from the laser generator on a disk substrate, and a converging optical element provided between the laser generator and the converging optical element. is a first reflection surface for reflection of the incident light beam that has been guided from the laser generating device is provided relative to the first reflecting surface, the light beam from the first reflecting surface
Includes a second reflecting surface for reflection, and the first entirely or reflection hologram formed on a part of the reflecting surface, and a light detecting means for detecting the light diffracted by the reflection hologram, The reflection between the normal line of the first reflection surface and the first reflection surface
The second reflection is substantially parallel to the optical axis of the emitted light;
The normal of the surface and the optical axis of the light reflected by the second reflecting surface are also substantially
Are almost parallel and are not diffracted by the reflection hologram.
The emitted light is together with the light reflected by the first reflecting surface.
A display is provided via the second reflection surface and the condensing optical element.
Illuminated on the substrate and diffracted by the reflection hologram
An optical pickup for monitoring and controlling the laser light output of the laser generator based on the output of the light detecting means that has detected light.