JP3271064B2 - Optical head, optical recording / reproducing device, and optical unit - 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 head , an optical recording / reproducing apparatus,
And an optical unit .

[0002]

2. Description of the Related Art FIG. 2 shows an example of the structure of an optical head in a conventional magneto-optical disk drive. The laser light emitted from the semiconductor laser 1 is collimated by the collimator lens 2, then enters the objective lens 4 via the beam splitter 3, and is focused and irradiated on the magneto-optical disk 5. The laser light reflected by the magneto-optical disk 5 enters the beam splitter 3 via the objective lens 4. The laser light reflected by the beam splitter 3 enters the beam splitter 8 via the half-wave plate 13, and a part of the light enters the photodetector 10 via the condenser lens 9. The remaining light is incident on the photodetector 12 via the condenser lens 11.
From the difference between the outputs of the photodetectors 10 and 12, a signal corresponding to the recorded information recorded on the magneto-optical disk 5 can be read.

On the other hand, a part of the light emitted from the semiconductor laser 1 and incident on the beam splitter 3 by the collimator lens 2 is reflected by the beam splitter 3 and is incident on the photodetector 7 via the condenser lens 6. So-called APC servo can be applied so that the output of the semiconductor laser 1 becomes constant from the output of the photodetector 7.

[0004]

As described above, in the conventional optical head, each component is arranged independently. As a result, there has been a problem that much effort is required to adjust the optical axis of each optical component.

The present invention has been made in view of such a situation, and is intended to simplify the adjustment.

The optical head of the present invention generates a laser beam.
Coupling a semiconductor laser and light generated by the semiconductor laser
Emitted by the collimating means for
An objective lens that irradiates the recording medium with the generated light and a collimator
Part of the light collimated by the
To the objective lens and collimate
Part of the light collimated by the
To control the output of the semiconductor laser
A first component guided to a first photodetector that outputs a signal
Separation means, reflected by the recording medium, and a first separation
The light transmitted through the means is separated and recorded on the recording medium.
Output a signal for reading a signal
Second separating means leading to a detector and a third photodetector
And a collimating means, a first separating means, and a
The separation means of (2) is integrally formed.
I do. The optical recording / reproducing apparatus of the present invention generates a laser beam.
Semiconductor laser and light generated by the semiconductor laser.
With collimating means to collimate and semiconductor laser
An objective lens that irradiates the recording medium with the generated light,
Integrated with the mate means,
A part of the collimated light is separated by reflection.
To the objective lens and collimate
Separation by transmitting part of the collimated light
Output a signal for controlling the output of the semiconductor laser.
First separating means for leading to a first photodetector,
Mate means and the first separating means are integrally formed,
Reflected by the recording medium and transmitted through the first separating means
Splits the light and reads the signal recorded on the recording medium.
A second photodetector that outputs a signal to
Second separating means for leading to a third photodetector.
It has an optical head. Optical unit of the present invention
Unit collimates the light generated by the semiconductor laser
Collimating means and integrated with the collimating means
Of the light collimated by the collimating means
Are separated by reflection and guided to the objective lens.
Part of the light collimated by the collimating means
Through the laser beam to separate the output of the semiconductor laser.
For the first photodetector that outputs a signal for control
A first separating means for guiding, a collimating means and a first separating means.
Integrated with the separating means, reflected by the recording medium,
In addition, the light transmitted through the first separating means is separated and the recording medium is separated.
Outputs signals for reading signals recorded on the body
To the second and third photodetectors
And second separating means.

[0007]

In the optical head, the optical recording / reproducing apparatus, and the optical unit having the above-described structures, the light generated by the semiconductor laser is used.
Collimating means, collimating hand
By reflecting some of the light collimated by the steps
To the objective lens and collimate
By transmitting part of the light collimated by the step
Signal for controlling the output of the semiconductor laser
First separating means leading to a first photodetector that outputs
Step, and a first separation reflected by the recording medium
The light transmitted through the means is separated and recorded on the recording medium.
Output a signal for reading a signal
Second separating means leading to a detector and a third photodetector
Are integrally formed.

[0008]

FIG. 1 is a sectional view showing the structure of an embodiment of the optical head according to the present invention. As shown in the figure, the optical head of the present invention includes a light emitting / receiving section 20, an alignment section 30, and an objective lens 41.

The light emitting and receiving unit 20 has a semiconductor laser 21 and a photodetector 22 for focusing, and a hologram 23 having, for example, astigmatism and grating characteristics is attached to the surface thereof.

An alignment unit 30 includes a collimator lens 31, a total reflection mirror 32, a beam splitter 33,
34, a total reflection mirror 35, a photodetector 36 for APC control, photodetectors 37 and 38 for detecting a magneto-optical signal, and a half-wave plate 39 are integrally formed. The substrate 40 of the alignment unit 30 has a structure in which a circuit for processing the outputs of the photodetectors 36 to 38 is built.

The diverging laser light emitted from the semiconductor laser 21 is converted into parallel light by a collimator lens 31, reflected by a total reflection mirror 32, and made incident on a beam splitter 33. The beam splitter 33 is configured by, for example, a half mirror or the like. Therefore, a part of the light passes through the beam splitter 33 and is incident on the photodetector 36 for APC control. A part of the light is reflected by the beam splitter 33 and is focused and irradiated on the magneto-optical disk 42 via the objective lens 41.

The laser light reflected from the magneto-optical disk 42 is incident on the beam splitter 33 via the objective lens 41, and the laser light transmitted therethrough is converted into a half-wave plate 39.
And is incident on the beam splitter 34. The beam splitter 34 is, for example, a deflection beam splitter, and a part of the light (for example, an S-wave component) is reflected and incident on the photodetector 37. The remaining light (P-wave component) passes through the beam splitter 34 and passes through the total reflection mirror 3.
5 and is reflected there and incident on the photodetector 38.

The collimator lens 31, the total reflection mirror 32, the beam splitters 33 and 34, the total reflection mirror 35, and the photodetector 36 housed in the alignment unit 30.
Light to the 38 th and １ ／ wavelength plates 39 are all parallel light. As a result, these positional adjustments may be relatively rough, and the positional relationship once set remains unchanged since they are integrally fixed. As a result, the optical axis adjustment as the optical head only needs to be performed between the light emitting and receiving unit 20, the alignment unit 30, and the objective lens 41. Furthermore, since the parallel light is incident on the photodetectors 36 to 38, a condensing lens is not required, so that the number of parts can be reduced, and the size and cost can be reduced.

Next, the operation will be described. The laser light emitted from the semiconductor laser 21 is
And is incident on the collimator lens 31, where it is converted from divergent light into parallel light. The parallel light is reflected by the total reflection mirror 32 and is incident on the beam splitter 33. Part of the light transmitted through the beam splitter 33 is incident on the photodetector 36 as parallel light. The output of the photodetector 36 is compared with a predetermined reference value, and the output of the laser diode 21 is controlled so that the difference is constant (AP
C control).

On the other hand, the laser light reflected by the beam splitter 33 is transmitted through the objective lens 41 to the magneto-optical disk 4.
2 is focused and irradiated. The laser light reflected by the magneto-optical disk 42 enters the beam splitter 33 via the objective lens 41. Some of the light is beam splitter 3
3, the light is reflected by the total reflection mirror 32, and is incident on the collimator lens 31. Then, the laser light emitted from the collimator lens 31 enters the hologram 23.

As described above, the hologram 23 is provided with grating and astigmatism characteristics. Therefore, some light is diffracted and given astigmatism, and is incident on the photodetector 22. Therefore, a focus error signal can be generated from the output of the photodetector 22 based on the so-called astigmatism method. Focus control is performed by driving a holder (not shown) that holds the light emitting / receiving section 20, the alignment section 30, and the objective lens 41 in the focus direction (vertical direction in the figure) in response to the focus error signal.

On the other hand, a part of the light incident on the beam splitter 33 passes therethrough and passes through the half-wave plate 39, whereby the polarization plane is rotated by 45 degrees. A part (S wave component) of this laser light is
4 and is incident on the photodetector 37. Further, the rest (P-wave component) of the light incident on the beam splitter 34 is transmitted therethrough and becomes a total reflection mirror 35.
And is incident on the photodetector 38. From the output difference between the photodetectors 37 and 38, an RF signal (P wave component) corresponding to the magneto-optical information recorded on the magneto-optical disk 42 can be reproduced.

When the disc to be reproduced is a CD or an optical video disc, the half-wave plate 39, the beam splitter 34, the photodetector 37 and the like can be omitted.

In this embodiment, laser light is detected by the photodetectors 36 to 38 in a state of parallel light. When the diameter of the laser beam is large, the diameters of the photodetectors 36 to 38 also become large. However, when these are increased, it becomes difficult to detect a high-frequency signal due to the stray capacitance. Therefore, the diameter of the laser beam (the diameter of the objective lens 41 and the collimator lens 31) is preferably 3 mm or less.

[0020]

As described above, according to the optical head, the optical recording / reproducing apparatus and the optical unit of the present invention, the collimating hand
The step, the first separating means, and the second separating means
The adjustment is simplified because the first and second parts are formed. In addition, miniaturization becomes possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an optical head according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of an example of a conventional optical head.

[Explanation of symbols]

 Reference Signs List 20 light emitting / receiving section 21 laser diode 22 photodetector 23 hologram 30 alignment section 31 collimator lens 32 total reflection mirror 33, 34 beam splitter 35 total reflection mirror 36 to 38 photodetector 41 objective lens 42 magneto-optical disk

Claims (3)

(57) [Claims] 1. A semiconductor laser for generating a laser beam and collimating the light generated by the semiconductor laser.
Collimating means for irradiating the recording medium with light generated by the semiconductor laser
And a part of the light collimated by the collimating means.
When separated by reflection and guided to the objective lens,
In both cases, the light collimated by the collimating means
The semiconductor laser is separated by transmitting a part of the semiconductor laser.
A first photo sensor for outputting a signal for controlling the output of the
First separating means for guiding to the detector, the first separating means being reflected by the recording medium, and
The light transmitted through the step is separated and recorded on the recording medium.
Output a signal for reading the signal
A second separating hand leading to a detector and a third photodetector
And a step, wherein the collimating means, the first separating means, and the
Second separating means, characterized by being integrally formed
And the optical head. 2. A semiconductor laser for generating a laser beam and collimating light generated by the semiconductor laser.
Collimating means for irradiating the recording medium with light generated by the semiconductor laser
An objective lens, and the collimating means.
Reflecting part of the light collimated by the
And guided to the objective lens,
Part of the light collimated by the collimator is transmitted
To control the output of the semiconductor laser.
To the first photodetector that outputs a signal for controlling
First separating means, integral with the collimating means and the first separating means.
Is configured to be reflected by the recording medium, and
Separating the light transmitted through the first separating means,
Output a signal to read the signal recorded on the
To the second and third photodetectors
And an optical head having a second separating means.
Optical recording and reproducing device. 3. A laser beam generated by a semiconductor laser.
Is guided to the objective lens and recorded by the objective lens.
The light applied to the recording medium and reflected by the recording medium
The optical unit leading to the first to third photodetectors
And collimates the light generated by the semiconductor laser.
A collimating means, wherein the collimating means and being integrally formed, said collimating
Reflecting part of the light collimated by the
And guided to the objective lens,
Part of the light collimated by the collimator is transmitted
To control the output of the semiconductor laser.
The first photodetector for outputting a signal for controlling the first photodetector
A first separating means for guiding the, integrally with the collimating means and said first separating means
Is configured to be reflected by the recording medium, and
Separating the light transmitted through the first separating means,
Output a signal to read the signal recorded on the
The second photodetector and the third photodetector.
And a second separating means for guiding to the
Optical unit.