JPS62173645A - Pickup head in optical information processor - Google Patents

Abstract

PURPOSE:To solve various problems due to aberrations based on the difference in refractive index by providing an aberration compensating plate between a substrate and a disk. CONSTITUTION:An aberration compensating plate 10 is provided on a substrate 1 and is fixed to the substrate 1 by a proper means. Materials having the same refractive index as that of a substrate 21 of an optical disk 20, preferably, the same materials as the substrate 21 are used as materials of the compensating plate 10, and the thickness of the compensating plate 10 is approximately equalized to that of the substrate 21. The light emitted from a lens 2 passes the compensating plate 10 and goes toward the optical disk 20 and reaches pits 24 through the substrate 21 of the optical disk 20, and the light reflected on pits 24 passes the substrate 21 and the compensating plate 10 and is received by a light receiving part 3 on the substrate 1. Aberrations due to the projected light and the reflected light based on the difference in refractive index between air and the substrate 21 are solved by the compensating plate 10.

Description

Detailed Description of the Invention Summary of the Invention In a pickup head including an optical system for projecting light onto a disk and a light receiving system for receiving reflected light from the disk on one substrate, there is a structure between the substrate and the disk. An aberration compensation plate is provided.

BACKGROUND OF THE INVENTION This invention focuses a laser beam from a semiconductor laser or the like, irradiates the information recording section of an optical disk, and reads information on the optical disk based on changes in the intensity of the reflected light. The present invention relates to a pickup write head in an optical information processing device, typically a device for writing or reading data.

The applicant has already made many proposals for this type of optical information processing device. For example, patent application No. 59-184778
, 59-184777, 59-193662. Same 6
0-110270-110275. 60-17318
2 etc. These optical information processing devices basically emit light from an optical system formed on a substrate and apply the light obliquely or perpendicularly to the disk surface, and a light receiving system formed on the same substrate emits light onto the disk surface. It is equipped with a pickup head that receives reflected light from a surface diagonally or vertically, and based on the signal output from the light receiving system, it can obtain information recorded on the disc and control signals for focusing and tracking. get. This pickup head.

It is attached to the focusing and tracking drive mechanism, and performs focusing control to accurately focus the projected light on pits, etc. on the disk surface based on the above control signals, and focuses the projected light on pits, etc. arranged in a spiral shape. Tracking control is performed to follow the spot.

Many of the above-mentioned pickup heads project light that is obliquely incident on the disk surface and receive light that is obliquely reflected from the disk surface. Since the light passes diagonally through the air and inside the disk substrate, the difference in the refractive index of these media causes aberrations between the projected light and the reflected light.In particular, the aberration of the projected light may cause the spot to become blurred or There is a problem with distortion.

SUMMARY OF THE INVENTION The present invention aims to solve the problems caused by aberrations caused by the above-mentioned refractive index difference.

This invention provides a pickup head that includes an optical system for projecting light onto a disk and a light receiving system for receiving reflected light from the disk on one substrate, in which an aberration compensating plate is provided between the substrate and the disk. It is characterized by This compensator has a refractive index that is the same as the refractive index of the disk substrate.
Most preferably, it is made of the same material as the disk substrate.

By providing this aberration compensation plate, the occurrence of aberration due to the difference in refractive index mentioned above can be suppressed to a minimum, making it possible to form a minute and clear spot of projected light on the disk, making it possible to create a more accurate spot. Optical information processing becomes possible.

DESCRIPTION OF THE EMBODIMENTS In this embodiment, the present invention is applied to a head of an optical pickup device that irradiates an information recording portion of an optical disc with a spot light and reads information on the optical disc based on changes in the intensity of the reflected light. For the sake of simplicity, we will discuss the beam method.

FIG. 1 shows a cross section of this optical pickup head.

The substrate 1 is a material that is transparent to the light used.

They are made of glass or plastic, for example, and are bent in the middle. This means that the emitted light, which will be described later, is from the lens 2.
is emitted perpendicularly to the surface of the substrate 1, and the optical disc 20
This is to allow the reflected light from to enter the light receiving section 3 perpendicularly. This substrate 1 is fixed on a suitable base, and this base is attached to a focusing and tracking drive mechanism (both paths shown).

As is well known, the optical disc 20 is made up of a disk-shaped transparent substrate 21 in which a large number of pits 24 representing information to be recorded are arranged in a spiral shape.
A vapor deposited aluminum film 22 is formed thereon, and this is further covered with a protective film 23.

A micro φ lens, such as a micro Fresnel lens 2, is formed on a part of the substrate 1, and one end of an optical fiber 4 is peeked out below. Light from a light source such as a semiconductor laser is guided to the optical fiber 4, and this light is emitted from the one end of the optical fiber 4, spreads, and passes through the substrate 1 toward the lens 2. This light is emitted into the air through the lens 2 and is condensed by the lens 2 to form a minute spot (for example, about 1 μm in diameter). The positional relationship between the optical disc 20 and the substrate 1 is determined so that this spot is exactly located at the pit 24 of the optical disc 20.

For example, one end of the optical fiber 4 is inserted into a hole pre-drilled on the bottom surface of the substrate 1, and the optical fiber 4 is attached to the substrate 1 with adhesive.
Fixed. The microlens 2 can be manufactured, for example, by electron beam φ lithography. That is, a conductive film is formed on the substrate 1, and an electron beam resist is uniformly applied thereon. Then, a predetermined interference fringe pattern is drawn on the resist using an electron beam drawing device controlled by a computer. Thereafter, when the resist is developed, a portion of the resist remains, resulting in a lens structure having corrugations of the interference fringe pattern.

The resist pattern may be transferred to the substrate 1 by dry etching the substrate 1 from above the lens pattern resist. Of course, the lens 2 may be formed by forming a hemispherical convex portion or four portions instead of using such a corrugated lens. Further, the lens 2 and the substrate 1 can be integrally made by injection molding.

A light receiving section 3 is also formed on the substrate 1.

This light receiving section 3 is for receiving the reflected light from the information recording surface of the optical disc 20, and is provided at a position where it can receive the light reflected diagonally downward from the spot position of the above-mentioned emitted light. ing. The light-receiving section 3 is composed of several independent light-receiving elements, and these light-receiving elements are made by, for example, depositing amorphous Si on the substrate 1. The output signal from one light receiving element or the sum signal of the output signals of several light receiving elements is transmitted to the optical disc 20.
The output signals of some light receiving elements are used to detect focusing errors and tracking errors.

In addition to amorphous Si, the light-receiving element can also be used as a light-receiving element.

CdTe, CdS, etc. can also be used.

Several PN junctions (photodiodes) may be formed on a Si chip, and this Si chip may be bonded to the substrate 1''2 to serve as a light receiving section.

This is the basic configuration of a pickup head.

For example, the arrangement of the light receiving elements of the light receiving section 3, the detection of the various errors mentioned above, and the details of the focusing and tracking drive mechanisms are fully disclosed in the applicant's earlier application mentioned above.

Now, an aberration compensating plate 10 is provided on such a substrate 1, and is fixed to the substrate 1 by appropriate means. The material for this supplementary material 11flO has the same refractive index as the substrate 21 of the optical disk 20, preferably the same material. Further, the thickness is preferably about the same as that of the substrate 21.

The light emitted from the lens 2 passes through the compensating plate 1O to the optical disk 20, passes through the substrate 21 of the optical disk 20, and reaches the bit 24. The light reflected by this bit 24 is
Similarly, the substrate 1 passes through the substrate 21 and the compensation plate 10.
The light is received by the upper light receiving section 3. The compensator 10 substantially eliminates aberrations caused in the projected light and reflected light due to the difference in refractive index between the air and the substrate 21.

FIG. 2 shows another embodiment. here.

Instead of the optical fiber 4, a semiconductor laser 5 serving as a light source is provided directly on the substrate 1. Namely.

A recess is formed in the lower surface of the substrate 1, and a semiconductor laser 5 is inserted into the recess and fixed, for example, by adhesive. The compensating plate 10 has a substantially triangular cross section along the bent upper surface of the substrate 1, and a lens 2 is formed on the lower surface of the compensating plate 2.

In this way, the shape of the compensating plate etc. may be set so that aberrations are best eliminated.

Needless to say, the present invention is also applicable to a three-beam method in which three light beams are projected.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, and is a cross-sectional view of an optical pickup head, and FIG. 2 is a cross-sectional view of an optical pickup head showing an example of the shape. 1...Substrate, 2...Lens, 3...
Light receiving section. 10... Aberration compensation plate, 20... Optical disc. Patent applicant: Tateishi Electric Co., Ltd. 1 Agent: Ken Tsukasa Ushiku and 1 other person Figure 1, Figure 1g2

Claims (1)

[Claims] An optical system comprising an optical system for projecting light onto a disk and a light receiving system for receiving reflected light from the disk on one substrate, characterized in that an aberration compensation plate is provided between the substrate and the disk. A pickup head in an information processing device.