JPH0240153A - magneto-optical pickup device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magneto-optical pickup device that records and reproduces information by irradiating the surface of a magneto-optical disk with laser light emitted from a semiconductor laser.

2. Prior Art A conventional magneto-optical pickup device is shown in FIGS. 4 and 5 (a).
)(b)(c)(cl).

First, the overall structure will be described. Linearly polarized laser light emitted by the semiconductor laser 1 while polarized in a predetermined direction is converted into parallel light by the coupling lens 2, transmitted through the beam splitter 3, and focused into a spot of approximately 1 μm by the objective lens 4. The light is emitted and is recorded on a magneto-optical disk 5 as an optical information recording medium. Further, the reflected light reflected by the magneto-optical disk 5 is subjected to the Kerr effect, and its plane of polarization is rotated by .fllk. The reflected light is separated by a beam splitter 3 via an objective lens 4 and guided to a reproduction optical system 6. In this reproduction optical system 6, the reflected light is condensed by a condenser lens 7, and λ/2
After the polarization plane is rotated by 45° by passing through the plate 8, the P-polarized light wave and the S-polarized light wave are separated by a Wollaston prism 9 as an optical element and guided to the light-receiving element 10, which is divided into two.

Reproduction is performed by detecting a magneto-optical signal as a differential output by the light receiving element 10.

Next, a description will be given of how the state of the polarization plane of the laser light emitted from the semiconductor laser 1 changes. In this case,
The problem is only the rotation of the plane of polarization without considering changes in the intensity of light.

FIG. 5(a) shows the state of the P polarization plane when emitted from the semiconductor laser 1, and FIG. 5(b) shows the state of the P polarization plane when emitted from the semiconductor laser 1.
This shows the state of the P-polarized light plane after passing through the laser beam, and at this time the laser beam has not yet rotated. Further, FIG. 5(c) shows a state in which the plane of polarization is rotated by ±θ with respect to the P polarization direction due to reflection by the magneto-optical disk 10 and being subjected to the Kerr effect. Furthermore, FIG. 5(d) shows a state in which the plane of polarization of the laser beam is rotated by 45 degrees by passing through the λ/2 plate 8. By rotating the polarization plane of the laser beam by 45 degrees using the λ/2 plate 8 in this way and detecting the magneto-optical signal using the differential method, the maximum number of signals can be obtained.

Problems to be Solved by the Invention However, in the case of the conventional device as described above, in order to differentially detect the magneto-optical signal, the λ/2 plate (phase shifter) 8 is Alternatively, the polarization plane of the laser beam is rotated by 45° using an optical rotator (not shown), but in this case, it is necessary to use such a retarder 8 and optical rotator, which increases the number of parts. There is a problem in that it is costly.

Means for Solving the Problems Therefore, in order to solve such problems, claim 1
The invention described above locates a rotatably mounted semiconductor laser or beam splitter at a position where the plane of polarization of laser light emitted from the semiconductor laser and incident on the beam splitter forms a constant angle with respect to the plane of polarization of the beam splitter. It was fixed in place.

In addition, the invention according to claim 2 provides an optical element and a light-receiving element that are rotatably attached such that the polarization plane of the reflected light reflected by the optical information recording medium and guided to the light-receiving element is the laser light emitted from the semiconductor laser. It was fixed at a position forming a constant angle with respect to the plane of polarization.

Accordingly, according to the invention as claimed in claim 1, by rotating the semiconductor laser or the beam splitter to change the angle between the polarization plane of the laser beam and the polarization plane of the beam splitter, the magneto-optical signal detected by the light receiving element can be changed. It is now possible to adjust the intensity to its maximum value, which eliminates the need to use a phaser or optical rotator as in the past, reducing the number of parts and creating a device that is inexpensive, compact, and lightweight. Can be done.

Further, from the invention as claimed in claim 2, the optical element and the light receiving element are integrated and rotated in the same direction, and the angle formed by the polarization plane of the laser light emitted from the semiconductor laser and the polarization plane of the reflected light guided to the light receiving element is adjusted. By changing this, it is possible to adjust the intensity of the magneto-optical signal detected by the photodetector to its maximum value.This eliminates the need to use a phaser or optical rotator as in the past, reducing the number of parts. It is possible to obtain a device that is inexpensive, small, and lightweight.

Embodiment An embodiment of the invention set forth in claim 1 will be described based on FIGS. 1 and 2. FIG. Note that the same reference numerals are used for the same parts as in the prior art, and the explanation thereof will be omitted.

The semiconductor laser 1 is rotatably mounted.

This semiconductor laser 1 is rotated so that the polarization plane of the laser beam forms a constant angle ψ=45° with respect to the P polarization plane (or S polarization plane) as the polarization plane of the beam splitter 3, and is fixed at this position. be done. As a result, the P polarization plane of the laser light emitted from the semiconductor laser 1 enters the beam splitter 3 at an angle ψ=45°. The method of rotating the polarization plane of the semiconductor laser 1 is to rotate it by an angle ψ within the plane in which the semiconductor laser 1 is attached. In addition, in the case of this embodiment, λ
/2 board 8 is not used.

In such a configuration, a change in the rotational state of the P polarization plane of the laser beam emitted from the semiconductor laser 1 will be described. First, FIG. 2(a) shows that the polarization plane of the laser beam emitted from the semiconductor laser 1 is incident on the P polarization plane of the beam splitter 3 at an angle ψ=45°. It is something that By setting ψ=45° in this manner, the strength of the magneto-optical signal becomes maximum, and the detection sensitivity can be further increased. In addition, Fig. 2 (b
) shows the state after the laser light passes through the beam splitter 3, and in this case, the angle formed by the P polarization plane remains the same as at the time of emission, ψ = 45°. There is. Furthermore, FIG. 2 (Q) shows a state in which the laser beam is reflected by the magneto-optical disk 5 and rotates only ±θ due to the Kerr effect. The light passes through the Wollaston prism 9 and is guided to the light receiving element 10.

In this case, the waveform shown in FIG. 2(c) is λ/2 of the conventional example.
It is possible to achieve the same state as the waveform shown in FIG. 4(d) when plate 8 is used.
It becomes possible to detect magneto-optical signals by simply rotating the semiconductor laser 1 and changing the angle of its polarization plane without using the plate 8.

Therefore, it is possible to reduce the number of parts and obtain an inexpensive, small, and lightweight device.

In addition, in the case of the above-mentioned embodiment, the beam splitter 3 is
Although the half mirror has a P-polarized light transmittance (P-polarized light reflectance) of 50% and an S-polarized light transmittance (S-polarized light reflectance) of 50%, the present invention is not limited to this. For example, the P-polarized light transmittance may be a%, If the P-polarized light reflectance is b%, the S-polarized light transmittance is 0%, and the S-polarized light reflectance is d%, the optimal angle ψ of the plane of polarization of the laser beam incident on the beam splitter 3 is For the P polarization plane of 3, ψat an-1(a b/cd) □-(1).

Thereby, the angle ψ of the plane of polarization immediately before the light enters the Wollaston prism 9 can be made the same as the angle when the λ/2 plate 8 is used as in the conventional example.

Further, in the above-described embodiment, the semiconductor laser 1 is mounted in a rotatable state, but instead of this, the semiconductor laser 1 is fixed and the beam splinter 3 is mounted in a rotatable state. Since the angle formed between the polarization plane of the laser beam and the polarization plane of the beam splinter 3 can be changed by rotating the laser beam relative to can.

Next, an embodiment of the invention according to claim 2 will be described with reference to FIG. This shows a modification of the invention set forth in claim 1.

That is, in the case of this embodiment, the semiconductor laser 1 and the beam splitter 3 are kept fixed, and the Wollaston prism 9 and the light receiving element 10 as optical elements are rotatably attached. And those Wollaston prisms 9
Then, the light receiving element 10 is rotated in the same direction, and the polarization plane of the reflected light reflected by the magneto-optical disk 5 and deflected by ±θ due to the Kerr effect becomes ψ= with respect to the polarization plane of the laser light emitted from the semiconductor laser 1. 45°, and light receiving element 1
By leading to 0, it is possible to obtain the same effect as the embodiment described in claim 1 described above. Note that as an optical element, in addition to the Wollaston prism 9, for example, a polarizing beam splitter (not shown) may be used.

Effects of the Invention The invention described in claim 1 provides a rotatably mounted semiconductor laser or beam splitter in which the polarization plane of laser light emitted from the semiconductor laser and incident on the beam splitter is relative to the polarization plane of the beam splitter. By rotating the semiconductor laser or beam splitter and changing the angle between the polarization plane of the laser beam and the polarization plane of the beam splitter,
It is now possible to adjust the intensity of the magneto-optical signal detected by the light receiving element to its maximum value, which eliminates the need to use conventional phasers and optical rotators, reducing the number of parts. This makes it possible to obtain an inexpensive, small, and lightweight device.

In addition, the invention according to claim 2 provides an optical element and a light-receiving element that are rotatably attached such that the polarization plane of the reflected light reflected by the optical information recording medium and guided to the light-receiving element is the laser light emitted from the semiconductor laser. Since the optical element and the light-receiving element are fixed at a position that forms a certain angle with respect to the polarization plane of By changing the angle between the reflected light and the polarization plane, it is possible to adjust the intensity of the magneto-optical signal detected by the photodetector to its maximum value. Since there is no need to use a child, the number of parts can be reduced and an inexpensive, small, and lightweight device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment according to claim 1, and FIG.
a), (b), and (c) are explanatory diagrams showing the rotational state of the polarization plane of the laser beam, FIG. 3 is a plan view showing an embodiment according to claim 2, and FIG. 4 is a plan view showing a conventional example. Figure 5(a)(b)
), (c) and (d) are explanatory diagrams showing the rotational state of the polarization plane of the laser beam. 1. Semiconductor laser, 3. Beam splitter, 4.
・Objective lens, 5... Optical information recording medium, 6... Reproduction destination system, 9... Optical element, 10... Light receiving element, ψ・
・Constant angle

Claims (1)

[Claims] 1. Laser light emitted from a semiconductor laser while polarized in a predetermined direction is focused by an objective lens through a beam splitter and irradiated onto an optical information recording medium to utilize its magneto-optic effect. At the same time, the reflected light from the optical information recording medium is separated by the beam splitter and guided to the reproduction optical system, and the guided reflected light is guided to the light receiving element via the optical element. In an optical information recording and reproducing device that detects and reproduces magnetic signals, the semiconductor laser or the beam splitter is rotatably mounted so that the polarization plane of the laser light incident on the beam splitter is the polarization plane of the beam splitter. A magneto-optical pickup device characterized in that it is fixed at a position forming a constant angle with respect to a surface. 2. Information is recorded by emitting laser light polarized in a predetermined direction by a semiconductor laser, focused by an objective lens through a beam splitter, and irradiated onto an optical information recording medium. Optical information recording in which the reflected light from the medium is separated by the beam splitter and guided to a reproduction optical system, and the guided reflected light is guided to a light receiving element via an optical element to detect and reproduce a magneto-optical signal. In the reproducing device, the polarization plane of the reflected light reflected by the optical information recording medium and guided to the light receiving element through the rotatably mounted optical element and the light receiving element is the polarization plane of the laser light emitted from the semiconductor laser. A magneto-optical pickup device characterized in that it is fixed at a position forming a constant angle with respect to a surface.