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:
May. 18, 1999
Filed:
Mar. 06, 1997
Yoriyuki Ishibashi, Kawasaki, JP;
Kabushiki Kaisha Toshiba, Kawasaki, JP;
Abstract
An optical disc apparatus is provided by putting together two substrates with a combined thickness 'h', as a recording medium. The two substrates each have a signal mark or a reflective layer which is capable of being the signal mark at least on the backside of the substrates. A laser beam is radiated onto the optical disc through an objective lens, and a reflected light from the reflective layer is detected by means of an optical detection device. One output of the optical detection device is supplied to a signal reader; the other of output thereof is supplied to a focusing apparatus for detecting a focus error of the objective lens and for controlling the positions of the objective lens with respect to the optical disc. Further, in the optical disc apparatus, if a principal wavelength of laser beam source is set as .lambda..sub.0 ; a half-width of laser beam source is set as .DELTA..lambda.; a numerical aperture of the objective lens is set as NA; and a refractive index of substrate material is set as n.sub.2, the half-width .DELTA..lambda. of the laser beam source satisfies the following equation:
Data source: USPTO (United States Patent and Trademark Office) public patent records. Weekly synchronization. How IDiyas builds this profile