JPH05120722A - Signal light receiving method for optical head - Google Patents

Abstract

PURPOSE:To reduce the loss of signal received light quantity to the stagnation of a dust and a stain, etc., and to stably detect a signal by deviating and arranging a photodetector from a lens focusing position and defocusing a converged beam on the surface of the photodetector. CONSTITUTION:After a laser beam 4 reflected from a disk transmits through the optical element 1 of a beam splutter, etc., and a lens 2, converges to the photodetector 3. In such a case, the photodetector 3 is arranged a little to the lens from the focusing position 2a of the lens 2. In such a state, since the diameter of the laser beam on the cover glass 3a of the photodetector 3 is larger than the same by conventional technique, the loss of the receiving light quantity to the stagnation of a dust and a stain, etc., is reduced and the signal is detected stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal receiving method for an optical head for an optical disk.

[0002]

2. Description of the Related Art In general, an optical head for an optical disk detects a signal from a disk by condensing signal light using a lens, disposing a light receiving element at the focal position of the lens. FIG. 5 is a drawing showing a conventional embodiment, 1 is an optical element such as a beam splitter, 2 is a lens, 3 is a light receiving element, 4
Is a laser beam. The laser beam 4 reflected from the disk passes through the optical element 1 and the lens 2 and is focused on the light receiving element 3 arranged at the focal position 2 a of the lens 2.

[0003]

In the conventional signal receiving method for an optical head for an optical disk, when dust or dirt adheres to the surface of the light receiving element, the signal may be remarkably deteriorated or the signal may not be reproduced. . The present invention avoids the above-mentioned drawbacks.

[0004]

SUMMARY OF THE INVENTION The present invention is an optical head for an optical disc for detecting a signal by condensing signal light reflected from a disc on a light receiving element by using a lens, and focusing the light receiving element on the lens. The feature is that it is placed at a position defocused from the position.

[0005]

【Example】

(Embodiment 1) FIG. 1 shows an embodiment of the present invention, in which 1 is an optical element such as a beam splitter, 2 is a lens, 3 is a light receiving element, and 4 is a laser beam. The laser beam 4 reflected from the disk passes through the optical element 1 such as a beam splitter and the lens 2, and then is focused on the light receiving element 3. FIG. 2 is a detailed view of the light receiving element portion of FIG. In this embodiment, the light receiving element 3 is arranged closer to the lens 2 than the focal position 2a of the lens 2. In this state, even if dust or dirt adheres to the surface of the cover glass 3a of the light receiving element 3, the cover glass 3a
Since the laser beam diameter above is larger than the conventional technology,
The amount of received light is reduced. Further, as shown in FIG. 3, the light receiving element 3 may be arranged at a position farther from the lens 2 than the focus position 2a.

(Embodiment 2) An embodiment shown in FIG. 4 is a MO signal light receiving portion of an optical head for a magneto-optical disk according to the present invention, and
This is applied to the tracking error signal light receiving part.
The laser beam 4 emitted from the laser emission source 7 is
Collimator lens 8, prism 9, splash prism 1
0, after passing through the objective lens 11, it is focused on the disk 12. First, in the MO signal light receiving section, the laser beam 4 reflected from the disk 12 passes through the objective lens 11 and the flip-up prism 10 and then enters the prism 9, and after passing through the Wollaston prism 13 and the lens 2, the light receiving element 3 Focus on. In the present embodiment, the beam diameter on the light receiving element 3 is expanded from about 20 μm to about 50 μm by disposing the light receiving element 3 on the lens 2 side by 0.5 mm from the focal position of the lens 2. As a result, even if dust of several tens of μm adheres, the signal can be received. Similarly, in the tracking error signal light receiving portion, the laser beam 4 reflected from the disk 12 passes through the objective lens 11 and the flip-up prism 10 and then enters the prism 9, and passes through the prism 14, the lens mask 18, and the lens 19. rear,
The light is collected on the light receiving element 20. Also in this embodiment, the light receiving element 20
Is arranged on the lens 19 side with respect to the focal position of the lens 19. In addition, application to disk heads other than magneto-optical disks is also conceivable.

[0007]

As described above, in the optical head for an optical disk of the present invention, the light receiving element is arranged so as to be displaced from the focal position of the lens, and the converging beam on the light receiving element surface is defocused, so that dust and dirt can be obtained. It is possible to reduce the loss of the amount of light received by the signal against the adherence of the like, and it is possible to perform stable signal detection.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a partial detailed view of FIG. 1 showing an embodiment of the present invention.

FIG. 3 is a partial detailed view of FIG. 1 showing an embodiment of the present invention.

FIG. 4 is a diagram showing an example of the present invention.

FIG. 5 is a diagram showing a conventional example.

[Explanation of symbols]

 1 optical element 2, 16 and 19 lens 2a focal position 3, 17 and 20 light receiving element 3a cover glass 4 laser beam 5 head housing 6 light receiving element plate 7 laser emission source 8 collimator lens 9 and 14 prism 10 rebound prism 11 objective lens 12 disk 13 Wollaston prism 15 Cylindrical lens 18 Lens mask

Claims (3)

[Claims] 1. In an optical head for an optical disc for detecting a signal by condensing signal light reflected from a disc onto a light receiving element 3 using a lens 2, the light receiving element 3 is moved from a focal position 2a of the lens 2 A method for receiving a signal from an optical head, which is characterized in that it is arranged at a defocused position. 2. The signal receiving method for an optical head according to claim 1, wherein the light receiving element 3 is arranged in a reproduction signal light receiving portion. 3. The signal receiving method for an optical head according to claim 1, wherein the light receiving element 3 is arranged in a tracking error signal light receiving portion.