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. 15, 2005
Filed:
Jul. 21, 2004
Yasuyuki Sugi, Naka-gun, JP;
Takesuke Maruyama, Yokohama, JP;
Yasuyuki Sugi, Naka-gun, JP;
Takesuke Maruyama, Yokohama, JP;
Hitachi Maxell, Ltd., Ibaraki, JP;
Abstract
When the DVD provided with the DVD substratehaving thickness tof 0.6 mm is installed in the optical disc apparatus, the light beamhaving wavelength λ=655 nm is used as luminous flux of numerical aperture NA=0.63 to be condensed on the information surfaceon the DVD substrate. When the CD provided with the CD substratehaving thickness tof 1.2 mm is installed in the optical disc apparatus, the light beamhaving wavelength λ=790 nm is effectively used as luminous flux of approximate numerical aperture NA=0.45 to be condensed on the information surfaceon the DVD substrate. The wavefront aberration caused by a thickness difference between the DVD substrateand CD substrateis canceled out by the chromatic aberration caused by a wavelength difference between the light beamsand. Therefore, in spite of the difference in the transparent substrates, the light beams are suitably condensed respectively on the information surfaceand