JPH05205339A - Magnetooptical recording polarization optical system - Google Patents

Abstract

PURPOSE:To provide the magnetooptical recording polarization optical system capable of producing a small size and thin type magnetooptical recording pickup. CONSTITUTION:When light 28 is made incident upon a polarization film 15, where p-polarized light is transmitted to be made incident upon a photodiode 13, while s-polarized light is reflected to be made incident upon a 1/4 wavelength plate 17. This s-polarized light is reflected by a total reflection film 18 and is reciprocated in the 1/4 wavelength plate 17 to become the p-polarized light, which is, therefore, transmitted through the polarization film 15 to be made incident upon a photodiode 14. Consequently, when the light 28 inclined by 45 deg. in the polarizing direction to an incident surface of the polarization film 15 is used, a component of a polarization plane which is not rotated by a magnetooptical disk 29 is equally divided into the photodiodes 13 and 14. Consequently, the magnetooptical recording pickup can be produced, and moreover, this can be small-sized and thin structive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization 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 capable of repeatedly recording and erasing information. As a pickup for recording and reading information on such a magneto-optical disc, one in which components such as a polarization beam splitter are assembled and fixed by adhesion or the like has been conventionally known.

[0003]

However, it is difficult to reduce the size and thickness of the conventional pickup in which the parts are assembled. The pickup for reproducing the compact disc is made by using a laser coupler in which a laser diode, a micro prism and the like are integrated.
However, a laser coupler for a compact disc is a non-polarized optical system, and it is impossible to make a magneto-optical recording pickup that reads recorded information from rotation of a polarization plane of reflected light.

[0004]

A polarization optical system 22 for magneto-optical recording according to the present invention includes first and second light receiving elements 13 and 14 formed on a semiconductor substrate 12 and at least these first and second light receiving elements. Is provided on the light receiving elements 13 and 14, and transmits the first light, which is linearly polarized light, as well as the first light.
Is a linearly polarized light whose polarization plane is orthogonal to the second polarizing film 15, which reflects the second light, a prism 16 arranged on the polarizing film 15, and the polarizing film 15 of the prism 16. Quarter-wave plate 17 provided on the side surface
And a total reflection film 18 disposed on the quarter-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.
Of the light 28, only the first light
The light passes through the polarizing film 15 and enters the first light receiving element 13.

Of the light 28 incident on the polarizing film 15, the second
Light 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,
It again passes through the quarter-wave plate 17. Therefore, the second light travels back and forth through the quarter-wave plate 17 to become the first light.

The light 28 that has emerged from the quarter-wave plate 17 and has traveled through the prism 16 and has been incident on the polarizing film 15 is the first light, so that it passes through the polarizing film 15 and becomes the second light. It is incident on 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 plane of incidence of the polarizing film 15, the component whose polarization plane is not rotated by the magneto-optical recording medium 29 becomes 1 and second light receiving element 1
It is divided into 3 and 14 by half.

[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 magneto-optical recording laser coupler 11 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 composed of three portions A to C and DF which are 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. The polarizing film 15 transmits only p-polarized light and reflects s-polarized light. A micro prism 16 having a trapezoidal cross section having a height of about 1 mm and an inclination angle of 45 ° is adhered on the polarizing film 15 above the photodiodes 13 and 14.

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 may be provided on the photodiode 13 and 14 on the upper surface of the Si substrate 12. Only, or on the lower surface of the micro prism 16, the photodiodes 13, 1
It may be provided only in the portion corresponding to 4.

A quarter wave plate 17 is attached to the upper surface of the micro prism 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 micro prism 16. A phase film made of a polymer film with uniform alignment may be used instead of the quarter-wave plate 17.

The above is the polarization optical system 22 for magneto-optical recording of the present embodiment. In order to construct the laser coupler 11 for magneto-optical recording, the polarization optical system 22 is arranged on the polarizing film 15 at a position facing the slope of the micro prism 16. Si substrate 23 different from Si substrate 12
Is fixed with silver paste or the like.

A photodiode 24 is formed on the upper surface of the Si substrate 23, 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
It is polarized light in which the electric field component is inclined by 45 ° with respect to the incident surface of the polarizing film 15. The light 28 enters 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 the magneto-optical disk 29 by the objective lens 26,
The polarization plane is rotated by the 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 light is reflected.
Only the non-polarizing film 21 is transmitted.

The light 28 transmitted through the non-polarizing film 21 travels through the micro prism 16 and enters the polarizing film 15. Of the light 28 incident on the polarizing film 15, only p-polarized light passes through the polarizing film 15 and enters 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 micro prism 16, passes through the quarter-wave plate 17, enters the total reflection film 18, and is reflected by the total reflection film 18. It again passes through the quarter-wave plate 17. That is, light 28
Travels back and forth through the quarter-wave plate 17 to become p-polarized light.

The light 28 reflected by the total reflection film 18 travels through the micro prism 16 and is incident on the polarizing film 15. Since the 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 can be obtained by the differential detection of RF = (A + B + C)-(D + E + F).

Further, when the magneto-optical recording pickup 27 and the magneto-optical disk 29 are in the in-focus state, FIG.
Since the light 28 is focused on the total reflection film 18 as shown in, the focus error signal is obtained by the 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, when the magneto-optical recording medium is irradiated with light whose polarization direction is inclined by 45 ° with respect to the incident surface of the polarizing film, the magneto-optical recording medium is formed. The components whose polarization plane is not rotated are distributed to the first and second light receiving elements in half.

Therefore, the rotation of the plane of polarization 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 the magneto-optical recording pickup can be manufactured. Moreover, since the semiconductor chip level assembly can be performed, a small and thin magneto-optical recording pickup can be manufactured.

[Brief description of 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]

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

Claims (1)

[Claims] 1. A first and a second formed on a semiconductor substrate.
And a first light receiving element that is provided on at least these first and second light receiving elements, transmits the first light that is linearly polarized light, and is linearly polarized light whose polarization plane is orthogonal to the first light. A polarizing film for reflecting the second light, a prism arranged on the polarizing film, and a quarter-wave plate provided on the surface of the prism opposite to the polarizing film, A polarization optical system for magneto-optical recording comprising a total reflection film arranged on a quarter-wave plate.