The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 09, 1993
Filed:
Jan. 03, 1992
Sony Corporation, Tokyo, JP;
Abstract
Laser light beams from first and second laser light sources 11 and 12 having different wavelengths are synthesized by a dichroic mirror 16 and irradiated on a magneto-optical disc 20 as a recordable disc and the reflected light is separated into the laser light of the first and second wavelengths. In respect of the laser light of the first wavelength, the phase difference between the P- and S-polarization components produced by the dichroic mirror 16 is compensated by a phase compensation plate 32 and the P-and S-polarization components are separated from each other by a polarization beam splitter 36 so as to be received by photodetector elements 37 and 38, respectively. Such dichroic mirror 16 is used in which the difference between the minimum transmittance in a working range of the laser light of the first wavelength and the maximum transmittance in a working range of the laser light of the second wavelength is 90% or higher for reducing changes in the phase difference between the P- and S-polarization components. Optimum signals may be obtained at the photodetector elements 37 and 38 while high wavelength separation characteristics are maintained.