JPS59112440A - Optical sensor for three-beam type optical pickup - Google Patents

Abstract

PURPOSE:To obtain an inexpensive optical beam pickup by forming an optical sensor for a three-beam type optical pickup by one two-split optical sensor for detecting a focus error signal, and two optical sensors for detecting a tracking error signal. CONSTITUTION:Three beams emitted from a diffraction grating plate 3 are diverged through an objective lens 6 and a disk 7, converged again by a converging lens 9, +1, 0 and -1-order lights A-C (Y axis) become A'-B' (Y axis) by an optical sensor surface 11, and since there is no cylindrical lens, an array axis of the beam is not twisted. A center light spot is photodetected like a semicircle by two-split optical sensor 11A for detecting a focus error signal. It is split into two by a split line parallel to a chord of a semicircle-like photodetecting pattern, and a position of the split line is determined so that optical outputs of #1 and #2 at the time of focusing become equal. The two-split optical sensor 11A and optical sensors 11B, 11C are placed on the Y axis, and a four-split optical sensor pattern can be formed by these sensors.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical sensor for a 3-beam optical pickup, and in particular, the central light spot is received in a semicircular manner, and the central light spot is received by a dividing line parallel to the chord of the semicircular shape. One two-split optical upper sensor for detecting a focus error signal, which is divided into two parts so that the light output of the subject is equal when in focus, and an optical sensor 2 for detecting a tracking error signal, in which the outer light spot is received in the form of a complete circle.
The present invention relates to an optical sensor for a 3-beam optical pickup consisting of:

There is a conventional 3-beam optical pickup as shown in Figure 1. That is, the emitted light (S wave) from the semiconductor ray f1 is passed through the collimator lens 2, the diffraction grating plate 3, and so on. It is polarized by 90 degrees through the polarizing beam splitter 4, circularly polarized by the quarter-wave plate 5, and focused on the disk 7 through the objective lens 6. It becomes linearly polarized light (P wave) after passing through the lens 6 , ]/4 wavelength plate 5 , travels straight through the polarizing beam splitter 4 , is deflected by 90° by the 90° deflection mirror 8 , passes through the converging reflex lens 1 which is a plano-convex lens, and then passes through the cylindrical lens 6 . The light is received by the split light sensor 11.

The force emitted from the diffraction grating plate 6 is +1.0. -3 of primary light
As shown in Figure 2, the beam is converged by the objective lens 6, diverges after passing the disk 7, and reaches the disk 7.
The reflected light is converged again by the objective lens 6, converged again by the converging lens 9, and reaches A, B, and O on the Y axis of the X, Y, and Z orthogonal three-axis system by the cylindrical lens 10, respectively. Then profit.

0, -1st order light slot) A, B, 0 are cylindrical lenses 10 and 9
With a 0° twist and a 6-split optical sensor 11, A' and "
, C' respectively.

Then, the focus error signal Fe is sent to the adder AD,
The output difference (11
] +# 3-# 2-J 4. ), and the tracking error signal Te is obtained from the output difference (#6-J5) of the 6-split optical sensor 11 via a subtracter SB.

In this way, the three-beam method that uses the cylindrical lens 10 to obtain the astigmatic focus error signal Fe requires the cylindrical lens indispensable for processing the 90° twisting of the three-beam light, and also requires optical axis adjustment. However, since precision is required for the arrangement of each optical component, there is a problem in that it is expensive.

The present invention has been made by focusing on the problems of the prior art, and is based on an optical sensor consisting of one two-split optical sensor for detecting focus error signals and two optical sensors for detecting tracking error signals. The present invention aims to solve the above-mentioned problems by providing a cylindrical lens and excluding a cylindrical lens.

The present invention will be explained below based on the drawings.

FIG. 3 is a diagram showing ray course tracking and the arrangement of optical sensors in the present invention.

In FIG. 3, the position of the cylindrical lens is indicated by a two-dot chain line, and +1. , (The three beams of 1st and -1st order light are converged by the objective lens 6 and diverge after passing the disk 7, and the reflected light from the disk 7 is converged again by the objective lens 6, and then again by the converging lens 9. converged, +1
．． o, -1st order lights A, , R, O (Y axis) are A', B' on the optical sensor surface 11.

0' (Y axis) Because there are so many cylindrical lenses, the beam alignment axis is twisted.

11A is a two-split optical sensor for detecting a focus error signal, and the central light spot receives light in a semicircular shape. 11. by the dividing line parallel to the chord of the semicircular light receiving pattern. +2
The position of the dividing line is determined so that the light outputs #i and #2 are equal when the first focus is on. The focus error signal Fe is obtained from (+2→l) via a subtracter SB.

Reference numerals 1113 and 110 are optical sensors for detecting a tracking error signal, and the outer light spot is received in the form of a complete circle. The tracking error signal Fe is converted to (1
1B-110).

The two-split optical sensor 11A, the optical sensor 11B, and 110 are arranged on the Y-axis, and these form a four-split optical sensor nomiturn.

In the present invention, a cylindrical lens is not required, the optical axis can be easily adjusted, and the number of optical sensor lead-out lines can be reduced to 5 instead of 7 in the conventional 6 elements + reverse bias terminal.

FIG. 4 shows the two-split optical sensor 11A and the optical sensor 11B at the distance between the objective lens and the disk.

The magnitude of the light receiving no-turn of 110 and the focus error signal Fe is indicated by a meter, and the A column indicates when the subject is too close, the B column indicates when the subject is in focus, and the 0 column indicates when the subject is too far away. In addition, the information signal RF
is the sum output (
+2+41).

The dividing line of the two-split optical sensor 11A does not have to be perpendicular to the row line of the three-beam light spots as shown in FIG.
It may be parallel as shown in Fig. 5, or may be rotated as shown in Fig. 6.

Note that when the light spot of the optical sensor 11 is as small as φ100 μm or less, if the width of the dividing line of the two-split optical sensor 11A is 10 μm, the width of element #1 will be about 15 μm, making it difficult to fabricate the optical sensor. Therefore, as shown in FIG. 7, an optical sensor 11A corresponding to the three-beam light spot,
11B and 110 are arranged evenly, a dividing line is provided slightly offset from the array center axis for the two-split optical sensor 11A, and half is divided with an aluminum vapor-deposited film (indicated by diagonal lines) so that the central light spot is received in a semicircular manner. It is easier to create if it is coated.

As described above, the present invention provides an optical sensor for a 3-beam optical pickup that includes one two-split optical sensor for detecting focus error signals and two optical sensors for detecting tracking error signals. By forming such a structure, it is no longer necessary to use a cylindrical lens which is expensive and whose optical axis is difficult to adjust, thereby achieving the effect that a three-beam type optical pickup can be made at a low cost.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an outline of a conventional 3-beam optical pickup, Fig. 2 is a diagram showing the ray course tracking and optical sensor arrangement of a conventional 3-beam optical pickup, and Fig. 3 is a diagram showing the arrangement of the optical sensor of the conventional 3-beam optical pickup. FIG. 4 is a diagram showing the light path tracking and the arrangement of the optical sensor in the invention; FIG. 4 is a diagram showing the light reception pattern of the optical sensor and the magnitude of the focus error signal at the separation distance between the objective lens and the disk; FIGS. 5 and 6 7 is a diagram showing how to draw a dividing line, and FIG. 7 is a diagram showing a method for creating a two-split optical sensor. 11... Optical sensor, 11A... 2-split optical sensor, 1
1B, 110... Optical sensor for tracking error signal detection Patent applicant Akai Electric Co., Ltd. 71

Claims (1)

[Claims] ■ A central light spot is received in a semicircular shape and is divided into two parts by a dividing line parallel to the chord of the semicircular shape, so that the light output of the person in focus is equal.
An optical sensor for a 3-beam optical pickup consisting of one split-light upper sensor and two optical sensors for detecting tracking error signals whose outer light spots are received in a complete circle.