JPS59223956A - Optical pickup of optical disk player - Google Patents

Abstract

PURPOSE:To stably convert information on an optical disk into an electric signal even when the temperature changes and the conversion is made under a high humidity condition, by fixing a photodetector to a metallic base plate having the same coefficient of linear expansion as a base table which holds a lens has. CONSTITUTION:The photoreceiving section of a photodetector 5 is so fine that it cannot read information when the photodetector 5 moves, but, since the same kind of material as that for making a base table 1 is used for making a copper coated aluminium base plate 6 and their coefficients of linear expansion are the same, the relative positional relation between the photoreceptor section and the base table 1 does not change even when the temperature changes. Therefore, discrepancy in the light condensing can be minimized extremely. Moreover, since the copper coated aluminum base plate does not absorb moisture, dimensional change due to humidity does not occur. Therefore, information of an optical disk can be read correctly even when the temperature is either high or low and at places where the humidity is high.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical pickup for an optical disc player that projects a light spot onto a disc-shaped recording medium to optically read information.

Conventional configuration and its problems In general, in this type of optical disk player, light emitted from a laser passes through a half mirror, is focused by a focus lens, becomes a spot on the disk, and the reflected light passes through an objective lens. After being reflected by a half mirror, the light passes through a detector lens and is focused onto a photodetector.

Page 2 Conventionally, this photodetector was attached to a substrate made of a resin material such as phenol, which has a different storage expansion coefficient than the base that holds the lens, so that when the temperature changes or moisture is absorbed, the photodetector does not move correctly on the photodetector. I couldn't focus the light.

OBJECTS OF THE INVENTION An object of the present invention is to provide a light pickup that can accurately focus reflected light onto a photodetector regardless of temperature and humidity.

Structure of the Invention The present invention is an optical pickup fixed to a metal substrate having the same coefficient of linear expansion as a base holding a photodetector lens,
This prevents deviations due to temperature and humidity and allows reflected light to be accurately focused on the photodetector.

The explanatory diagram of the embodiment shows one embodiment of the present invention, in which a laser 2. No-fu mirror 3. Detector lens 4. A photodetector 37 and a photodetector 5 are attached with screws 7 via a copper-clad aluminum board 6.

The light emitted from the laser 2 passes through the half mirror 3 and is focused onto the disk by the objective lens 9 attached to the drive unit W8. The light focused on the disk is reflected by the disk, is reflected by the half mirror 3 by the objective lens 9, passes through the detector lens 4, and is focused onto the photodetector 5. The light focused on the detector is converted into an electrical signal by the photodetector 5, and the lead wire 1o is electrically connected by the printed pattern.
is output from.

The light-receiving part of the photodetector 5 is minute, so if the photodetector 6 moves even a little, it will no longer be able to read the information, but the copper-clad aluminum substrate 6 is made of the same material as the base 1 and has the same coefficient of linear expansion. Even if the temperature changes, the relative positional relationship with the base 1 does not change. Therefore, the deviation in focusing can be significantly reduced. Furthermore, since copper-clad aluminum substrates do not absorb heat, there is no dimensional change due to humidity.

Therefore, information on the disc can be read correctly even at high or low temperatures, or in damp or humid locations.

The copper-clad aluminum substrate referred to here is one in which an insulating layer is attached to an aluminum plate, and a copper foil is pasted on the insulating layer, and an electric circuit pattern is created by etching the copper foil.

Although a copper-clad aluminum substrate is used in this configuration example, other metals may be used as long as they have the same coefficient of linear expansion as the base that holds the lens. The circuit pattern may be formed by a plating method or the like. Although a half mirror is used in this configuration example, the same application is possible even when a polarizing beam splitter is used.

Effects of the Invention The present invention has a photodetector fixed to a metal substrate with a coefficient of linear expansion approximately equal to that of the base that holds the lens, so even if the temperature changes or it is used in a humid place,
The light focusing position on the photodetector does not change, so information on the disk can be stably converted into electrical signals.

[Brief explanation of drawings]

The figure on page 5 is a cutaway perspective view of essential parts of an embodiment of the present invention. 1...base, 2...laser, 3...
... Half mirror 14 ... Detector lens, 5 ... Photo detector, 6 ...
Copper-clad aluminum board, 7... Screws, 8...
Drive device, 9...Objective lens, 10...
·Lead.

Claims (1)

[Claims] An optical pickup for an optical disk player, which is fixed to a thin metal substrate.