Wavelength-selective phase grating type optical low-pass filter comprising adhesive layer between transparent layers
US5434709A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 4, 1993 |
| Grant date | Jul 18, 1995 |
| Priority date | — |
| Expiry date | Aug 4, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B5/1871
- WIPO fieldOptics
- WIPO sectorInstruments
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 …
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