JPS62241142A - Optical detection head - Google Patents

Abstract

PURPOSE:To improve the fidelity of digital reproduction and to improve the sound quantity and picture quality by providing a ray selection means allowing only the incidence of a ray reflected on a pit between an optical disk and an optical sensor. CONSTITUTION:A shield cover 14 formed as a cone is provided to the tip of a seat 10 supporting an objective lens 5, and an opening 15 leading only the reflected light beams from one pit 7 placed oppositely to the objective lens 5 is provided above the shield cover 14. Thus, only the reflected beams from the pit 7 placed above the opening 15 of the shield cover 14 are made incident on the objective lens 5 via the opening 15. For example, light beams shown in broken lines are reflected to block it from being made incident on the objective lens 5. Thus, the sound quality and picture quality are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a photodetection head that reads signals from an optical disk in which digital signals are stored in a large number of pits formed on the surface of the disk.

"Prior Art" As a conventional example of a CD player equipped with a photodetection head,
For example, there is one described in the book "Digital Audio" (see pages 316 to 317) published by Radio Gijutsu Co., Ltd.

That is, as shown in FIG. The light is guided to an objective lens 4 through an objective lens 4 (which has the function of rotating the light by 1/4 wavelength, that is, by 45 degrees), and is focused by this objective lens 5 onto a pit 7 of a disk 6.

Then, the light beam reflected by this pit 7 is again made into a parallel light beam by the zero-point objective lens 5, and then again
By passing the light through the wavelength plate 4, the polarization axis of the 1:1/4 wavelength is rotated. The direction of the light beam whose polarization axis has been rotated by 90 degrees is changed by the beam splitter 3, and is incident on the optical sensor 8, where it is read.

The beam splitter 3 has a function of separating laser beams with different polarization axes, and allows the light beam generated by the light source 1 to pass through to the objective lens 4 side, and reflects the light beam reflected at the pit 7 to condense the light beam. The light is guided to an optical sensor 9 via a lens 8.

Further, the objective lens 5 has a support provided movably in the front axis direction thereof, and is held by a seat IO, and a plurality of magnets 12 connected to each other by a magnetic path 11 are provided on the outer periphery of the seat IO. It is being

The receiver moves the objective lens 5 in the optical axis direction by energizing a focus adjustment coil I3 wound around the outer periphery of the seat IO to finely adjust the focus.

"Problems to be Solved by the Invention" By the way, the photodetection head of the above method cannot block the incidence of light beams other than the light beams to be detected from entering the objective lens 5. Diffuse reflection, diffused reflection, or plastic,
The light is diffused within the disk 6 made of transparent or semi-transparent material such as glass, and furthermore, the disk 6
External light propagated while being refracted within the lens may enter the objective lens 5, and there is a problem in that reading errors occur due to the incidence of such illegal optical signals.

The present invention was proposed in view of the above-mentioned circumstances, and an object of the present invention is to improve the fidelity of digital reproduction by preventing manual input of illegal optical signals other than the signals to be read.

"Means for Solving the Problems" In order to achieve the above object, the present invention provides a light beam selection means that allows only the light beam reflected by one pit to be incident between the optical disk and the optical sensor. This is what I did.

"Operation" The polarizing means prevents light rays other than those reflected by one pit from entering the condenser lens.

"Example" Hereinafter, the present invention will be described in detail with reference to the drawings. In addition,
In the figure, parts common to the conventional example are given the same reference numerals to simplify the explanation.

1 and 2 show a first embodiment of the present invention.

This photodetection head has a support plate supporting the objective lens 5.
A cone-shaped shielding cover 14 is provided at the tip of the O as shown in FIGS. 2(a) and 2(b), and this shielding cover 1
4 is provided with an opening 15 that guides only the reflected light from one pit 7 directly facing the objective lens 5. The shielding cover 14 selects light rays from a specific direction and directs them to the objective It is designed to function as a light beam selection means for guiding the light beam to the lens 5.

In the photodetection head of the first embodiment, only the reflected light from the pit 7 located above the opening 15 of the shielding cover 14 is reflected as shown by the solid line in FIG. In addition, other illegal optical signals that are incident on the objective lens 5 via the aperture 15, such as light rays that are refracted within the disk 6 and propagated from the disk (for example, as shown by the broken line in FIG. The external light incident from the outside light is reflected and prevented from entering the objective lens 5.

Next, FIG. 3 shows a second embodiment of the present invention, in which a cylindrical shielding cover 14A is provided around the objective lens 5,
A polarizing filter (polarizing lens) 16 is provided at the tip of the shielding cover 14A, which allows only polarized light in a specific direction (polarized light reflected by the pit 7 placed directly opposite the objective lens 5) to pass through. 16 is made to function as a light beam selection means.

The polarizing filter 16 allows the reflected light (having a fixed polarization direction) from the pit 7 placed directly opposite the polarizing filter 16 to enter the objective lens 5, as shown by the broken line in FIG. It is possible to prevent the occurrence of reading errors by regulating the incidence of unauthorized optical signals.

Furthermore, FIG. 4 shows a third embodiment of the present invention, in which a polarizing objective lens 17 which also has the function of the polarizing filter 16 in the second embodiment is used to filter light from a specific direction. It is designed to only allow the incidence of
Even with such a system, it is possible to prevent the incidence of unauthorized optical signals as in the first and second embodiments.

In the above embodiment, only the reflected light from one pit placed directly opposite the objective lens is allowed to enter, but the reflected light from other directions having a specific relative positional relationship with the objective lens is It may also be possible to allow only the incidence of light rays.

Furthermore, it goes without saying that the optical detection head of the present invention can be applied not only to compact discs but also to image storage devices and various other devices that require the detection of optical signals.

"Effects of the Invention" As is clear from the above explanation, the present invention provides a method for allowing light to enter only from one pit that has a specific positional relationship with respect to the objective lens between the optical sensor and the optical disk. Since a selection means is provided, it is possible to select between diffused transmitted light due to light rays diffused within the disk, refracted light from external light, and disk rotation.
It is possible to obtain good sound and image quality by preventing the detection of irregularly reflected light due to rotation, preventing a decline in the digital S/N ratio of the playback signal, a drop in the playback level, and a deterioration in the playback sound quality. This effect is achieved.

[Brief explanation of drawings]

1 and 2(a) and 2(b) show a first embodiment of the present invention, in which FIG. 1 is a longitudinal sectional view, FIG. 2(a) is a plan view of the shielding cover, and FIG. (b) is a vertical cross-sectional view of the shielding cover, FIG. 3 is a vertical cross-sectional view of the second embodiment of the present invention, FIG. 4 is a vertical cross-sectional view of the third embodiment of the present invention, and FIG. FIG. 2 is a longitudinal sectional view showing the principle of a CD player using a detection head. 5...Objective lens, 6...Disk,
7...Pit, 10...Uke is the seat, 14
・14A... Shielding cover, I5... Opening, 16... Polarizing filter, 17...
...Objective lens. Hiroshi Murayama Figure 2 Figure 4

Claims (1)

[Claims] In an optical detection head that reads data from an optical disk in which digital signals are stored in a large number of pits formed on the surface, an optical sensor is provided between the optical disk and an optical sensor that detects light rays emitted from a light source to the pits and reflected. , characterized in that a light beam selection means is provided for allowing a light beam reflected by one pit arranged at a specific relative position with respect to the objective lens to be incident on the optical sensor, and regulating the incidence of other light beams. A photodetection head.