JPS62209736A - Optical head for optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the number of parts, to reduce man-hours, and to improve accuracy, by attaching the function of a diffraction grating on a half prism nicking a grid, and forming the grid with accuracy. CONSTITUTION:Light beams emitted from a semiconductor laser 1 is made incident on a half prism 10, however,since a grid 10a is nicked on an incident plane, it is divided into plural diffraction light beams, and out of them, three light beams of 0th order and + or -1st order on which energy is concentrated, are used. Those beams are condensed on a disk 6 by an objective lens 5, and after they are reflected on the disk 6 plane, and their directions are changed by the prism 10, they arrive at an optical detector 8. And three diffraction light beams are condensed with angles against a bit string, and out of reflected light beams, the 0th order beams are made incident on photodetectors B1-B4 in the optical detector 8, and the + or -1st order beams, on light receiving parts A1-A2. At such a time, the 0th order beams are used as a signal on the disk 6, and the error signal of a focus servo, and the + or -ast order beams, as the error signal of a track servo by the signals of the light receiving parts A1-A2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application 1] The present invention relates to an optical head for an optical information recording/reproducing apparatus that records or reproduces information by condensing light beams onto a disk.

[Technology from IT 1 Figure 3 shows the optical system of a conventional optical head. 2) L holder (: Diffraction grating fixed in the mouth, (4) is a half-blizz L\, (t)
) is an objective lens, (6) is a disk, (7) is a magnifying lens, and (8) is a photodetector.

Next, the operation will be explained. After the light emitted from the semiconductor laser (1) enters the diffraction grating (2), it is split into a plurality of diffracted lights, but the optical 2F energy is concentrated in the 0th order and ±1st order,
Use the light beams of these three trees. The three light beams pass through the half prism (4), are focused on the disk (6) -1- by the objective lens (5), are reflected on the surface of the disk (6), and then are focused on the half prism (4). It changes direction and passes through the magnifying lens (7) to the photodetector (8).

As shown in Fig. 4(a), the diffracted lights of the three trees are focused on the disk (6) at an angle with respect to the pit row, and among the reflected lights, the 0th order light is shown in Fig. 4(a). As shown in b), the ±1st order light enters the light receiving elements 81 to B4 of the photodetector (8), and the ±1st order light enters the light receiving portions A1 to A2 Or1? lru.

The zero-order light is used as a signal on the disk and as an error signal for the focus servo. In addition, the +1st order light is a difference signal (IAl-
IA2) is created and used as an error signal for track 4 novo to ensure that the rack follows track 1.

[Problem that the invention attempts to solve] Since the conventional optical head is configured as shown below, it is necessary to accurately position the diffraction grating (2) on the optical axis. . Also, there is a knob (9) on the fourth part (3a) of the holder (3).
), insert the eccentric shaft (9a), and rotate this knob <9) in the direction of the arrow I! There were problems such as the need to adjust and cover the position of the diffraction grating (2).

The present invention has been made to solve the above-mentioned problems, and aims to provide an optical head that reduces the number of parts, reduces assembly time, and improves precision.

Means for Solving Problems] The optical head according to the present invention has a half prism -i/
ij += 18-f and match the h portion of the diffraction grating.
I made it so that I could hold it.

[Effect 1 IN this invention] Using a diffraction grating by carving a grating on the half prism (Jl/v) <1
<J: due to the diffraction phenomenon, the beam is split, +1st-order light for the error signal of the - rack servo is obtained, and the number of assembly parts is reduced due to the reduction in the number of parts, and the viscosity is also reduced.

[Example] Below, an embodiment of the invention will be explained with reference to the drawings.

In FIG. 1, in which the same parts as in FIG. 3 are given the same reference numerals, (10) is a half prism with a grating (10a) carved on the negative surface.

Next, the operation of the above embodiment will be explained. The light emitted from the semiconductor laser (1) enters the half prism (10), but since the grating (10a) is engraved on the entrance side,
It is divided into a plurality of diffracted lights, and uses three light beams, the 0th-order light and the +1st-order light, whose energy is to be concentrated.

3. The light beam of the tree is sent to the objective lens (5).
The light is focused on the disk (6) surface and reflected by the IL half prism (10) to change direction and reach the photodetector (8).

As shown in Fig. 2(a), the three diffracted lights are focused at an angle to the pit row on the disk (6), and among the reflected lights, the 0th order light is shown in Fig. 2(b). Not shown J: Injected into the light receiving element of the sea urchin photodetector (8), 13 to B4,
The 21st order light flows into the light receiving section Δ1-A2.

The zero-order light is used as a signal on the disk and as an error signal for focus servo. Also, the +1st order light is at the light receiving part Δ1
The -A2 signal is used as an error signal for the 1-rack servo.

[Effects of the Invention] As described above, according to the present invention, since a grating is carved into the half prism to give it the function of a diffraction grating, a dedicated diffraction grating is not required. In addition, by carving the grating with high precision during the manufacturing stage of the half prism, it is possible to omit the adjustment of the diffraction grating, reduce the number of component points τ 4 - and increase the precision lσ by 1. effective.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention. The optical system diagram of the head, Figures 2(a) and (b) are diagrams of the spot state on the disk and light receiving element due to the optical system, Figure 3 is the optical system diagram of the conventional optical head, and Figure 4(a), (b) is a state diagram of a spot on a disk and a light receiving element included in the optical system. In the figure, (1) is a light emitting source (semiconductor laser), (6
) is a disk, (1o) is a half prism, (10a)
is a grid. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] One side of a half prism that separates the light emitted from the light source and the light reflected from the disk in an optical head that is installed in an optical information recording and reproducing device and records or reproduces information by focusing a light spot on the disk. Carve a lattice into the
An optical head for an optical information recording/reproducing device, characterized in that the optical head also serves as a diffraction grating for producing a track servo error signal for causing the light spot to reliably follow a track on the disk.