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:
Oct. 29, 1996
Filed:
Jun. 05, 1995
Junji Tominaga, Nagano, JP;
Susumu Haratani, Chiba, JP;
Ryo Inaba, Nagano, JP;
Tsuneo Kuwahara, Nagano, JP;
TDK Corporation, Tokyo, JP;
Abstract
An optical information medium has on a substrate (2) with information-carrying pits (21), a light transmittance control layer (3) including a lower dielectric layer (31), a mask layer (32) and an upper dielectric layer (33). The mask layer has an original state before irradiation of reading light. Upon irradiation of a reading light beam to define a beam spot, the mask layer undergoes a crystal-to-crystal transition in a region (H) of the beam spot depending on the intensity distribution of the beam spot. Multiple reflection condition changes in the transition portion so that the beam spot contributing to read-out is limited to the transition or transition-free region (H or L). The transition temperature is in the range of 200.degree. to 450.degree. C. The mask layer returns to the original state after passage of the beam spot. The invention is also applicable to an optical recording medium having a recording layer above or below the transmittance control layer.