JPH0445132Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to an optical pickup device for reading information from an optical disk.

(b) Prior Art FIG. 1 is a diagram showing a conventional pickup device. In the figure, 1 is a semiconductor laser, 2 is a collimator lens, 3 is a diffraction grating, 4 is a polarizing beam splitter, 5 is a λ/4 plate, 6 is an objective lens 6, D is a disk, and 7 is a condenser lens. , 8 is a cylindrical lens, and 9 is a sensor. That is, in the past, the polarizing beam splitter 4 was used to guide the beam light output from the semiconductor laser 1 to the disk side and guide the beam light reflected from the disk to the sensor 9.

However, in such a conventional example, λ/4
Imperfections in the optical axis of plate 5, polarizing beam splitter 4
There was a possibility that the reflected beam light from the disk would return to the semiconductor laser 1 depending on the degree of the extinction ratio. In this case, if the semiconductor laser 1 is one that performs longitudinal single mode oscillation, the light returns,
The mode becomes unstable and generates noise, which adversely affects the reproduced signal.

(c) Purpose of the invention The present invention proposes a pick-up device with a novel configuration that can separate light incident on a disk and light reflected from the disk without using a polarizing beam splitter.

(d) Structure of the invention An optical system consisting of a transparent plate placed at the Brieucster angle with respect to the light reflected from the disk, and a half mirror attached to one side of a λ/4 plate tilted at 45° to the optical axis. The structure is such that the light is separated at two points.

(E) Embodiment FIG. 2 is a diagram showing an optical system for light separation according to the present invention. The semiconductor laser 1 has a laser chip 1a and a window of a transparent plate 1b. The transparent plate 1b is arranged at a Brewster angle θ with respect to the light reflected from the disk. The λ/4 plate 5 is arranged at 45° with respect to the optical axis, and a half mirror vapor deposited film 10 is formed on one side.

The beam light output from the semiconductor laser 1 is linearly polarized light (P polarized light), and the half mirror 10, λ/
By passing through the four plates 5, the light becomes circularly polarized light and irradiates the disk. The reflected beam light from the disk passes through the λ/4 plate 5 again and becomes linearly polarized light (S polarized light). This S-polarized light is half mirror 1
0, one returns to the sensor 9 side and the other returns to the semiconductor laser 1 side. However, since the transparent plate 1b constituting the window of the semiconductor laser 1 is arranged at the Brewster angle θ, the returned light (S-polarized light) is completely reflected at this portion and does not return to the laser chip 1a.

FIG. 3 is a diagram showing the overall configuration of a pickup using the above-mentioned optical system.

(f) Effects of the invention According to the invention described above, light can be separated with a simple configuration without using a polarizing beam splitter, and a pickup device with good characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional pickup device, FIG. 2 is a diagram showing a light separation optical system according to the present invention, and FIG. 3 is a diagram showing a pickup device using the optical system shown in FIG. 2. . 1 is a semiconductor laser having a transparent plate 1a, 5 is a λ/4 plate, 9 is a sensor, and 10 is a half mirror vapor deposited film.

Claims (1)

[Scope of utility model registration request] a semiconductor laser that emits a linearly polarized beam; a beam splitter that guides the beam emitted from the semiconductor laser to a medium and guides reflected light from the medium to a sensor; and a beam splitter that is disposed between the semiconductor laser and the medium. an optical pickup device comprising: a λ/4 plate; and a transparent plate attached to the exit window of the semiconductor laser at an angle of Brewster that substantially reflects the reflected light.