JPS59112441A - 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 three-split optical sensor for detecting a focus error signal, and two optical sensors for detecting a tracking error signal. CONSTITUTION:Three beams of +1, 0 and -1-order lights emitted from a diffraction grating plate 3 are converged by an objective lens 6, diverged from the part or its vicinity passing through a disk 7, converged again by the objective lens 6, converged again by a converging lens 9, the +1, 0 and -1-order lights A-C (Y axis) are reduced to A'-C' (Y axis) by an optical sensor surface 11, and since there is no cylindrical lens, the beam array is not twisted. A center light spot is photodetected like a full circle by a three-split optical sensor 11A. A focus error signal Fe is obtained from #3-#2-#4 through an adder AD1 and a subtracter SB1. The three-split optical sensor 11A and optical sensors 11B, 11C are placed on the Y axis, and a five-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 type original pickup, and in particular, a central light spot is received in the form of a complete circle, and two beams are received in parallel across the center of the complete circle. One 3-split optical sensor for detecting a focus error signal, which is divided into 3 parts by the dividing line of the book, and when in focus, the light output in the center part is equal to the sum of the light outputs on both sides, and the outer light spot is a complete circle. 3 consisting of two optical sensors for detecting tracking error signals received by
This invention relates to a base sensor for beam type base pickup.

There is a conventional three-beam optical pickup as shown in FIG. That is, the emitted light from the semiconductor laser 1 (
S wave) is a collimator lens 2, a diffraction grating plate 6. It is polarized by 90 degrees through a polarizing beam splitter 4, and then a quarter wavelength plate 5.
The reflected light becomes circularly polarized light, passes through the objective lens 6, and focuses on the disk 7, and the reflected light becomes circularly polarized light with the opposite rotation to the incident light. P
wave), which travels straight through the polarizing beam splitter 4 and rotates at 90°.
Deflected by 90° with a deflection mirror 8, and a converging lens 9, which is a plano-convex lens. The light passes through a cylindrical lens 10 and is received by a six-divided original sensor 11.

The three beams of lunar, O, and −1st-order light emitted from the diffraction grating plate 6 are converged by the objective lens 6 as shown in FIG. The light is converged again by the objective lens 6, converged again by the converging lens 9, and reaches A, B, and C on the X axis of the x, y, and z orthogonal three-axis system by the cylindrical lens 10, respectively. Then +1.0.
-] dimensional spots A, B, and O are twisted by 90 degrees with the cylindrical lens 10, and the 6-split optical sensor 11 has the dimensional spots A', l(
/.

Each reaches C7.

Then, the focus error signal Fe is sent to the adder AD,
Output difference (#) of the 6-split optical sensor 11 via the subtracter SB
The tracking error signal Te is obtained from the output difference (#6-45) of the six-divided optical sensor 11 via the 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 was made by focusing on the problems of the prior art, and provides an optical sensor consisting of one three-part optical sensor for detecting a focus error signal and two optical sensors for detecting a tracking error beam. The purpose of this invention is to solve the above problems by eliminating the cylindrical lens.

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

FIG. 3 is a diagram showing the arrangement of the optical sensor and the optical sensor according to 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 converged again by the converging lens 9. , +1.
0. - The primary light A, [3,0 (Y axis) is A/, ge on the optical sensor surface 11.

0' (Y axis), and the beam arrangement axis is not twisted because there are many cylindrical lenses.

11A is a three-split optical sensor for detecting a focus error signal, and a central light spot is received in a complete circle. The center of the circular light-receiving nomiturn is divided into three parts by two parallel dividing lines, and the optical output of the center well 3 and both ends +2. The position of the dividing line is determined so that the sum of +4 optical outputs is equal to the sum of the optical outputs.

The focus error signal Fe is sent to adders AD, , subtracter S
It is obtained from (+3−+ 2−+4 ) via B.

11B and 11Ci are optical sensors for detecting tracking error signals; The light is received in a complete circle.

The tracking error signal Fe passes through the subtracter SB2 (
1113-110). 3-split optical sensor 11
A. Optical sensor 11B.

i i cll-ty are arranged on the X axis, and a five-divided optical sensor nomiturn is formed by these.

The present invention does not require a cylindrical lens, and the optical axis can be easily adjusted.

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

The light receiving pattern of 110 and the magnitude of the focus error signal Fe are shown by meters, and the A column indicates when the subject is too close, the B column indicates the focus, and the 0 column indicates when the subject is too far. Note that the information signal RF is sent via the adder AD2 to the sum output of the 3-split optical sensor IIA (+2-143+#4.
).

The dividing line of the 3-split source sensor 11A does not have to be perpendicular to the column line of the 3-beam source spot as shown in FIG.
It may be parallel as shown in FIG. 5 or rotated as shown in FIG.

As explained above, in the present invention, the optical sensor for a 3-beam type original pickup is formed by one three-split optical sensor for detecting a focus error signal and two original sensors for detecting a tracking error signal. By doing so, there is no need to use an expensive cylindrical lens whose optical axis is difficult to adjust, and an effect can be obtained in that a three-beam type optical pickup can be performed 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 optical path tracing and optical sensor arrangement of a conventional 3-beam optical pickup, and Fig. FIG. 4 is a diagram showing the optical path tracking and the arrangement of the optical sensor in the invention, FIG. FIG. 6 is a diagram showing how to draw dividing lines. 11... Optical sensor, 11A... 3-split optical sensor, 1
113.110・Optical sensor for tracking error signal detection Patent applicant Akai Electric Co., Ltd.

Claims (1)

[Claims] 1. The central light spot is received in the form of a complete circle, and within the full circle +L>k, two parallel dividing lines
One 3-split optical sensor for detecting focus error signals, where the light output at the center of the carament is equal to the sum of the light output at both sides when focused, and a tracking error where the outer light spot is received in a complete circle. 3-beam type original pink-up sensor consisting of two optical sensors for signal detection