JP3355607B2 - Polarizing optical system for magneto-optical recording - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing optical system for magneto-optical recording suitable for use in a pickup for reading recorded information from a magneto-optical recording medium.

[0002]

2. Description of the Related Art A magneto-optical disk is known as one of recording media on which information can be repeatedly recorded and erased many times. As a pickup for recording or reading information on or from such a magneto-optical disk, a pickup in which components such as a polarizing beam splitter are assembled and fixed by bonding or the like is conventionally known.

[0003]

However, it is difficult to reduce the size and thickness of the conventional pickup in which components are assembled. A pickup for reproducing a compact disk is made using a laser coupler in which a laser diode, a microprism, and the like are integrated.
However, a non-polarizing optical system is employed in a laser coupler for a compact disk, and a magneto-optical recording pickup that reads recorded information from the rotation of the polarization plane of reflected light cannot be manufactured.

[0004]

A polarizing optical system 22 for magneto-optical recording according to the present invention comprises first and second light receiving elements 13 and 14 formed on a semiconductor substrate 12 and at least the first and second light receiving elements 13 and 14. of it provided over and in contact with the light receiving elements 13 and 14, and the first light while transmitting the first light is a linearly polarized light and reflects the second light which is linearly polarized light polarization planes are orthogonal A polarizing film 15, a prism 16 disposed on the polarizing film 15, a quarter-wave plate 17 provided on a surface of the prism 16 opposite to the polarizing film 15, A total reflection film 18 disposed on the half-wave plate 17.

[0005]

In the polarizing optical system 22 for magneto-optical recording according to the present invention, the light 28 whose polarization direction is inclined by 45 ° with respect to the incident surface of the polarizing film 15 is transmitted through the prism 16 to the polarizing film 15.
When only the first light out of this light 28 is
The light passes through the polarizing film 15 and enters the first light receiving element 13.

[0006] Of the light 28 incident on the polarizing film 15, the second
Is reflected by the polarizing film 15, travels through the prism 16, and enters the quarter-wave plate 17. The second light transmitted through the quarter-wave plate 17 is reflected by the total reflection film 18,
The light again passes through the quarter-wave plate 17. Therefore, the second light reciprocates in the quarter-wave plate 17 to become the first light.

The light 28 coming out of the quarter-wave plate 17 and traveling through the prism 16 and entering the polarizing film 15 is the first light, so that it passes through the polarizing film 15 and passes through the second film. The light enters the light receiving element 14. Therefore, when the magneto-optical recording medium 29 is irradiated with the light 28 whose polarization direction is inclined by 45 ° with respect to the incident plane of the polarizing film 15, the component whose polarization plane is not rotated by the magneto-optical recording medium 29 is 1st and 2nd light receiving element 1
Half and half are distributed to 3,14.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to a laser coupler for magneto-optical recording will be described below with reference to FIG.

As shown in FIG. 1A, in a laser coupler 11 for magneto-optical recording to which this embodiment is applied, two photodiodes 13 and 14 are formed on a Si substrate 12.
As shown in FIG. 1B, the photodiodes 13 and 14 are made up of three portions A to C and D to F divided in a direction perpendicular to the arrangement direction.

A polarizing film 15 is provided on the entire upper surface of the Si substrate 12. This polarizing film 15 transmits only p-polarized light and reflects s-polarized light. Above the photodiodes 13 and 14 on the polarizing film 15, a microprism 16 having a trapezoidal cross section and a height of about 1 mm and a slope angle of 45 ° is bonded.

The polarizing film 15 may be provided not on the entire upper surface of the Si substrate 12 but on the entire lower surface of the microprism 16, and on the portions of the upper surface of the Si substrate 12 above the photodiodes 13 and 14. Only, or the photodiodes 13, 1
4 may be provided only in the portion corresponding to 4.

A quarter-wave plate 17 is attached to the upper surface of the microprism 16, and a total reflection film 18 is formed on the quarter-wave plate 17. Also,
A non-polarizing film 21 having a reflectance of 50% is formed on the slope of the microprism 16. Note that a phase film using a polymer film having uniform alignment may be used instead of the quarter-wave plate 17.

The above is the polarization optical system 22 for magneto-optical recording according to the present embodiment. In order to constitute the laser coupler 11 for magneto-optical recording, a position opposing the inclined surface of the microprism 16 on the polarizing film 15 is required. Si substrate 23 different from Si substrate 12
Are fixed with silver paste or the like.

On the upper surface of the Si substrate 23, a photodiode 24 is formed, and a laser diode 25 is fixed by solder or the like. Further, such a magneto-optical recording laser coupler 11 and the objective lens 26 constitute a magneto-optical recording pickup 27.

The magneto-optical recording pickup 27 as described above.
Then, the light 28 emitted from the laser diode 25 is
The electric field component is polarized light that is inclined by 45 ° with respect to the incident surface of the polarizing film 15. The light 28 is incident on the non-polarizing film 21, and only 50% of the light 28 is reflected upward. In addition,
The photodiode 24 is for a so-called rear APC.

The light 28 reflected by the non-polarizing film 21 is condensed on a magneto-optical disk 29 by an objective lens 26,
The plane of polarization is rotated by a magnetic signal recorded on the magneto-optical disk 29. The light 28 reflected by the magneto-optical disk 29 enters the non-polarizing film 21 again, and 50% of the
Only passes through this non-polarizing film 21.

The light 28 transmitted through the non-polarizing film 21 travels in the micro prism 16 and enters the polarizing film 15. Of the light 28 incident on the polarizing film 15, only the p-polarized light passes through the polarizing film 15 and is incident on the photodiode 13;
The polarized light is reflected by the polarizing film 15.

The light 28 reflected by the polarizing film 15 travels through the microprism 16, passes through the quarter-wave plate 17, enters the total reflection film 18, and is reflected by the total reflection film 18. The light again passes through the quarter-wave plate 17. That is, light 28
Reciprocates in the quarter-wave plate 17 to become p-polarized light.

The light 28 reflected by the total reflection film 18 travels through the microprism 16 and enters the polarizing film 15, but since this light 28 is p-polarized as described above,
The light passes through the polarizing film 15 and enters the photodiode 14. Therefore, a magneto-optical signal is obtained by the differential detection of RF = (A + B + C)-(D + E + F).

When the magneto-optical recording pickup 27 and the magneto-optical disk 29 are in focus, FIG.
As shown in FIG. 7, since the light 28 is focused on the total reflection film 18, a focus error signal is obtained by differential detection of FE = (A + C + E)-(B + D + F).

[0021]

In the polarizing optical system for magneto-optical recording according to the present invention, if the magneto-optical recording medium is irradiated with light whose polarization direction is inclined by 45 ° with respect to the plane of incidence of the polarizing film, the magneto-optical recording medium can be used. The component whose polarization plane has not been rotated is distributed to the first and second light receiving elements by half.

Accordingly, the rotation of the polarization plane of the reflected light from the magneto-optical recording medium can be detected by the differential output of the first and second light receiving elements, and a pickup for magneto-optical recording can be manufactured. In addition, assembly at the semiconductor chip level can be performed, and there are only two light receiving elements.
In addition, since a polarizing film is provided in contact with these light receiving elements , a small and thin pickup for magneto-optical recording can be manufactured.

[Brief description of the drawings]

FIG. 1A is a side view of a magneto-optical recording pickup to which an embodiment of the present invention is applied, and FIG. 1B is a plan view of a photodiode in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Si substrate 13 Photodiode 14 Photodiode 15 Polarizing film 16 Microprism 17 Quarter-wave plate 17 18 Total reflection film 22 Polarizing optical system for magneto-optical recording 28 Light 29 Magneto-optical disk

Continuation of front page (56) References JP-A-5-144113 (JP, A) JP-A-4-362554 (JP, A) JP-A-3-214102 (JP, A) JP-A-64-46243 (JP) JP-A-5-36111 (JP, A) JP-A-4-177643 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 11/105 551 G11B 7/135

Claims (1)

(57) [Claims] And 1. A semiconductor substrate formed first and and second light receiving elements are provided in contact with at least the first and second on the light receiving element, the first light which is linearly polarized A polarizing film that transmits and reflects the second light that is linearly polarized light whose polarization plane is orthogonal to the first light, a prism disposed on the polarizing film, and the polarizing film of the prism A polarizing optical system for magneto-optical recording, comprising: a quarter-wave plate provided on the opposite surface; and a total reflection film disposed on the quarter-wave plate.