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:
Jul. 18, 1995
Filed:
Aug. 04, 1993
Matsushita Electric Industrial Co., Ltd., Osaka, JP;
Abstract
In a wavelength-selective phase-grating type optical low-pass filter including at least a pair of adjacent first and second transparent layers, there is provided at least one adhesive layer through which a pair of adjacent first and second transparent layers stacked on each other in a phase grating form for generating a phase difference distribution on the boundary surface between the pair of adjacent first and second transparent layers. The optical low-pass filter satisfies the following conditions under a condition of 470 nm<.lambda.<580 nm: (a) No (.lambda.)=Ni (.lambda.), (b) .nu.d1<.nu.d2 or .nu.d1>.nu.d2, and (c) 0.9< Np(.lambda.) / No(.lambda.)< 1.1, where .lambda. is a wavelength of light passing through the optical low-pass filter, No (.lambda.) and Ni (.lambda.) are refractive indexes of the first and second transparent layers, respectively, at the wavelength .lambda., .nu.d1 and .nu.d2 are Abbe's numbers of the first and second transparent layers, respectively, No(.lambda.) is a refractive index of the adhesive layer at the wavelength .lambda., Np(.lambda.) is a refractive index of either one of the first and second transparent layers at the wavelength .lambda., thereby obtaining such low-pass effects as preventing decrease of an MTF value of the wavelength band of green.