JPH06203420A - Magneto-optical detector - Google Patents

Abstract

PURPOSE:To unnecessitate the positioning process of optical parts and to miniaturize a detector by integrally joining a beam splitter film and a polarization beam splitter film to a medium surface for rotating the polarization plane of a returning light from a magneto-optical disk. CONSTITUTION:Beam splitter film 32 for optical branching and polarization beam splitter film 34 are adhered to both surfaces of a crystal member 33 so as to integrate them as a composite prism 40 and the prism is fixed on a substrate 36. An emitting light LA1 from a semiconductor laser 2 is reflected by the beam splitter film 32, converted on a magneto-optical disk 10 through an objective lens 8 and the reflecting light LA2 is again made incident on the crystal member 33 through the beam splitter film 32. Then, the polarization direction of the light is rotated by 45 deg., the light is introduced to the polarization beam splitter 34, split into a P-and S-polarization components, made incident on photodetectors 22, 24, respectively, and magnetic recording information is detected. Consequently, in the magneto-optical detector 30, by integrating the composite prism 40, the complicated positioning process of the optical parts is avoided and the detector is miniaturized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical detector, and is particularly suitable for application to a magneto-optical detector using a composite prism.

[0002]

2. Description of the Related Art Conventionally, in this type of magneto-optical detector, as shown in FIG. 4, reference numeral 1 denotes a magneto-optical detector as a whole, which emits an emission light beam LA1 from a semiconductor laser 2. Here, in the magneto-optical detector 1, the emitted light beam L
After A1 is converted into parallel rays by the relay lens 4 and the waveform shaping prism 5, it is transmitted through the beam splitter 6 and focused on the magneto-optical disk 10 through the objective lens 8.

The emitted light beam LA1 focused on the magneto-optical disk 10 is reflected while the plane of polarization is rotated according to the magnetic field intensity of the magneto-optical disk 10, and the return light L is generated.
A2 enters the beam splitter 6, is reflected here, and is transmitted through the half-wave plate 14. The return light LA2 is 1/2
When passing through the wave plate 14, the polarization direction of the half wave plate 14 is rotated by 45 ° and guided to the polarization beam splitter 16.

Therefore, in the polarization beam splitter 16, the return light LA2 is split into P-polarized light and S-polarized light, and is incident on the light-receiving elements 22 and 24 via the condenser lenses 18 and 20, respectively.

By receiving the return light LA2 by the two light receiving elements 22 and 24 as described above, the magneto-optical detection signal, the tracking error signal, and the focus error signal are detected from the detection results of the two light receiving elements 22 and 24. And so on.

[0006]

By the way, in the magneto-optical detector 1 having such a configuration, since the optical components (6, 14, 16) are formed separately from each other, the positioning of each optical component is performed. It is necessary to increase the accuracy, and the structure is inevitably complicated and the size is increased accordingly, and the positioning adjustment work of each optical component becomes complicated.

Further, there has been a problem that the assembled portion of the optical component is deformed due to environmental changes and the optical characteristics are easily changed.

The present invention has been made in consideration of the above points, and an object thereof is to propose a magneto-optical detector which is much smaller and can reduce the number of adjustment steps.

[0009]

In order to solve such a problem, according to the present invention, a light source 2 for emitting a predetermined light beam LA1 and a light beam LA1 are reflected in a magneto-optical disk direction 10 and at the same time, the magneto-optical disk 10 is provided. Beam splitter film 32 that transmits the return light LA2 reflected at
And a medium 33 that is joined to the beam splitter film 32 and that transmits the return light LA2 that has passed through the beam splitter film 32 by rotating the polarization plane of the return light LA2 by 45 degrees and that is joined to the medium 33 and that passes through the medium 33. LA2 is divided into first and second polarization components having different polarization directions, the first polarization component is made incident on the first light receiving element 22, and the second polarization component is reflected at the beam splitter film 32. After
The polarized beam splitter film 34 which is incident on the second light receiving element 24 is provided.

In the present invention, the medium 33 is the first
A beam splitter film 32 is formed on the surface 41, the amorphous medium 31 is bonded to a part of the first surface 41 via the beam splitter film 32, and the magneto-optical disk is formed via the amorphous medium 31. The return light from 10 is incident and the amorphous medium 31
The second polarized light component reflected by the polarized beam splitter film 34 is made incident on the beam splitter film 32 formed in the region where is not joined.

[0011]

By bonding the beam splitter film 32 and the polarized beam splitter film 34 to the medium 33, these optical systems can be integrated. Therefore, the complicated positioning process of the optical component can be avoided.

[0012]

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

In FIG. 1 in which parts corresponding to those in FIG. 4 are designated by the same reference numerals, numeral 30 indicates a magneto-optical detector as a whole, and a beam splitter film 32 for optical branching is formed on the first surface and The composite prism 40 in which the glass member 31 and the glass member 35 are fixed to a part of the first surface of the crystal member 33 having birefringence or optical rotatory power such as a crystal having the polarized beam splitter film 34 formed on the surface 2 is received. It is fixed on a substrate 36 on which the elements 22 and 24 are provided.

The area of the crystal member 33 to which the glass member 31 is fixed is approximately half of the inclined surface 41 of the crystal member 33.

In the above structure, the emitted light beam LA1 emitted from the semiconductor laser 2 passes through the glass member 31, is reflected by the beam splitter film 32, and is further focused on the magneto-optical disc 10 via the objective lens 8. Glow.

The emitted light beam LA1 focused on the magneto-optical disk 10 is reflected while the plane of polarization is rotated according to the magnetic field strength of the magneto-optical disk 10, and the return light L is generated.
A2 again enters the beam splitter film 32 through the glass member 31, passes through the beam splitter film 32, and then enters the crystal member 33.

When the return light LA2 passes through the crystal member 33, the polarization direction is rotated by 45 ° and guided to the polarization beam splitter film 34 due to the polarization characteristics (birefringence and optical rotatory power) of the crystal member 33.

Accordingly, the return light LA2 incident on the polarization beam splitter film 34 in the polarization direction inclined by 45 ° is P-polarized and S-polarized.
The P-polarized component is separated into polarized light and passes through the glass member 35 to enter the light receiving element 22. On the other hand, the S-polarized component reflected by the polarized beam splitter film 34 passes through the crystal member 33 and enters the beam splitter film 32. Here, the beam splitter film 32 is a crystal member 33.
And the S polarization component of the return light LA2 transmitted through the inside of the crystal member 33 is totally reflected by the boundary formed in the air, and the S polarization component of the return light LA2 is guided to the light receiving element 24. Get burned.

Since the P-polarized component and the S-polarized component separated in the polarized beam splitter film 34 respectively include the rotation of the polarization plane caused by the magnetic Kerr effect in the magneto-optical disc 10, as an opposite component, the light-receiving element 22 and the The recording magnetic domain on the magneto-optical disk 10 can be detected by detecting the difference between the light fluxes incident on 24.

That is, FIG. 2 shows the light receiving portions of the light receiving elements 22 and 24, each of which has three light receiving portions 22A, 22B and 2 respectively.
2C and 24A, 24B, and 24C, and a tracking error signal, a focus error signal, and R for the magneto-optical disk 10 according to the amount of light received at each light receiving unit.
The F sum signal (phase pit detection signal) and the RF difference signal (magneto-optical detection signal) can be detected.

Here, the amount of light received by the light receiving section 24A is A,
Letting B be the amount of light received by the light receiving unit 24B, C be the amount of light received by the light receiving unit 24C, D be the amount of light received by the light receiving unit 22A, E be the amount of light received by the light receiving unit 22B, and F be the amount of light received by the light receiving unit 22C. King error signal is (A-
C) + (FD), the focus error signal is represented by (A + CB)-(D + FE),
The RF sum signal is represented by (A + B + C) + (D + E + F), and the RF difference signal is (A + B + C)-(D + E + F).
Is represented by

Thus, in the magneto-optical detector 30, since the integrated composite prism 40 is fixed on the substrate 36, the optical members such as the beam splitter film 32 and the polarized beam splitter film 34 are complicated. It is possible to easily obtain a magneto-optical detection signal and the like without performing various positioning.

According to the above construction, the optical components such as the beam splitter film 32 and the polarized beam splitter film 34 are integrated into the composite prism 40, thereby avoiding the need for complicated positioning of the optical components. obtain. Therefore, the magneto-optical detector 30 can be further downsized.

It should be noted that in the above-described embodiment, each of the three
The case where the light receiving elements 22 and 24 having one light receiving section are used has been described, but the present invention is not limited to this, and for example, FIG.
, Four light receiving portions 52A, 52B,
You may make it use the light receiving elements 52 and 54 which have 52C, 52D and 54A, 54B, 54C, 54D.

In this case, the amount of light received by the light receiving portion 54A is A, the amount of light received by the light receiving portion 54B is B, the amount of light received by the light receiving portion 54C is C, and the amount of light received by the light receiving portion 54D is D,
Assuming that the light receiving amount of the light receiving unit 52A is E, the light receiving amount of the light receiving unit 52B is F, the light receiving amount of the light receiving unit 52C is G, and the light receiving amount of the light receiving unit 52D is H, the tracking error signal is ((A + B)-(C + D )) + ((G + H)
-(E + F)), the focus error signal is represented by (A + D- (B + C))-(E + H- (F + G)), and the RF sum signal is (A + B + C + D) + (E
+ F + G + H) and the RF difference signal is (A + B
+ C + D)-(E + F + G + H).

In the above-mentioned embodiments, the case where the glass members 31 and 35 are used has been described, but the present invention is not limited to this, and the point is to use various materials as long as they are amorphous media. You can

[0027]

As described above, according to the present invention, the beam splitter film and the polarized beam splitter film are bonded to the first and second surfaces of the medium that rotates the polarization plane of the return light from the magneto-optical disk. By doing so, it is possible to integrate an optical system that allows the return light from the magneto-optical disk to enter the light-receiving element, thereby avoiding the complicated positioning process of the optical parts, and further reducing the size of the magneto-optical detector. realizable.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a magneto-optical detector according to the present invention.

FIG. 2 is a schematic diagram showing a configuration of a light receiving element.

FIG. 3 is a schematic diagram showing a configuration of a light receiving element.

FIG. 4 is a schematic diagram showing a conventional magneto-optical detector.

[Explanation of symbols]

2 ... Semiconductor laser, 10 ... Magneto-optical disk, 22,
24 ... Light receiving element, 30 ... Magneto-optical detector, 31, 35
...... Glass member, 32 …… Beam splitter film, 33 ・ ・ ・
... Crystal member, 34 ... Polarized beam splitter film, 36 ...
…substrate.

Claims (2)

[Claims] 1. A light source which emits a predetermined light beam, a beam splitter film which reflects the light beam in the magneto-optical disk direction and transmits the return light reflected by the magneto-optical disk, and the beam splitter. A medium that is bonded to a film and rotates the polarization plane of the return light that has passed through the beam splitter film by rotating the polarization plane by 45 degrees and transmits the return light that has been bonded to the medium and that has transmitted through the medium in different polarization directions. After being separated into the first and second polarization components, the first polarization component is incident on the first light receiving element, and the second polarization component is reflected by the beam splitter film, A magneto-optical detector comprising a polarized beam splitter film which is incident on a light receiving element. 2. The above-mentioned medium, wherein the beam splitter film is formed on a first surface, and an amorphous medium is bonded to a part of the first surface via the beam splitter film. The return light from the magneto-optical disk was incident through the crystalline medium, and reflected by the polarized beam splitter film on the beam splitter film formed in the region where the amorphous medium was not joined. The magneto-optical detector according to claim 1, wherein the second polarized component is made incident.