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:
Jun. 25, 1996
Filed:
Apr. 25, 1994
Jun Kanehira, Tokyo, JP;
Olympus Optical Co., Ltd., Tokyo, JP;
Abstract
A recording film of a recording medium has tracks with a track pitch of 1.6 .mu.m. Each track has a land and a groove, and the width of each of the land and groove is about 0.8 .mu.m. The groove and land differ relatively in height by a degree corresponding to (2n-1)/4 (n: a natural number) times the wavelength of the irradiated beam. At the time of reproduction, reflected diffraction beam components reflected from the land and groove are provided with a phase difference .pi.. Thus, a peak of the diffraction beam is concentrated within the range of the NA of an objective lens, with high intensity. As a result, the presence/absence of pits located at a distance less than a diffraction limit, which have not been detected in the prior art, can be detected.