Laser head device

Abstract

The invention relates to a laser head device. It is an object of the present invention to provide a laser head device having good reproducing characteristics which can be reproduced almost without being affected by the birefringence even if an optical recording medium has birefringence. In the laser head device (1), the laser light (L1), (L2) reflected by the optical recording medium D returns through the objective lens (13), collimating lens (12), and upward reflecting mirror (11), and returns to the prism (6) again. ) after passing through the half-transmission and half-reflection mirror (7) to the light-receiving element (9). Here, the sum of the transmission efficiencies of the partial reflection surfaces (60) and (70) of the prism (6) and the half-mirror (7) for P-polarized light and S-polarized light is approximately equal. Therefore, stable playback characteristics can be obtained even when the optical recording medium D has birefringence.

Description

field of invention [0001] The invention relates to a laser head device in which laser light emitted from a laser light source is reflected on an optical recording medium, and the reflected light passes through a plurality of optical elements, or is guided into a light receiving element after being reflected. Background technique [0002] As optical recording media, CDs, CD-Rs, DVDs, and the like are known, which differ in recording forms such as substrate thickness and recording density. In order to play back a DVD with a high recording density, it is necessary to use a short-wavelength laser with a wavelength of 650nm or 635nm. Usually, a long-wavelength laser of 760 to 780 nm is used to play back a CD, but a CD can also be played back by using a short-wavelength laser for playing back a DVD. However, CD-R, which is a development form of CD and can be recorded or written, is designed according to the policy of obtaining the best performance by utilizing the long-wavelength...

AI Technical Summary

Problems solved by technology

However, the partial reflection surfaces 60, 70 of the prism 6 and the half-mirror 7 are formed by lamination of multilayer dielectric films. To make such partial reflection surfaces 60, 70 non-polarized, more than 30 layers of dielectric materials need to be formed. Thin film lamination, the price of such prism 6 and half mirror 7 will be quite high

In addition, due to the deviation in the production of each layer, as the number of layers increases, the deviation of the transmittance and reflectance characteristics will increase.

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