Patent US6194299B1 successfully refreshed from Google Patents.
EP0454409A1
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Wavelength selective phase grating optical low-pass filter
Assignee: Panasonic Holdings Corp
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Filing: 1991-04-23
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Granted: —
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Expires: 2011-04-23
Abstract
Abstract A phase grating optical low-pass filter having wavelength selectivity comprises a plurality of layers (8,9) which are the same in refractive index at a certain wavelength and different from one another in refractive index dispersion, and has a configuration to generate a phase difference at a boundary of the layers. Use : Low-pass filter for a single tube color camera, with enhanced spacial frequency in the green wavelength band.
Inventors
- 👤 Hiroaki Okayama
- 👤 Syusuke Ono
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 14:43
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/42; G02B27/4233; G02B27/4244; G02B27/46; G02B5/00; G02B5/18; G02B5/1866; G02B5/1871; G02B5/20; G02B5/28; G02B5/289
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
50 words
A wavelength selective phase grating optical low-pass filter having such a structure that at least two layers which are the same in refractive index at a certain wavelength and different in refractive index dispersion from one another are overlaid so that phase differences are generated at a boundary between them.
Claim 2
Dependent Claim
116 words
An optical low-pass filter according to Claim 1, wherein, in a certain wavelength λd in which the refractive indices of the materials of two layers are included in a wavelength range: 470 nm < λ < 580 nm assuming the refractive index of the layer on an object side to be N₁(λd) and the refractive index of the layer on an image side to be N₂(λd), the following relation is satisfied: N₁(λd) = N₂(λd), and assuming the Abbe's number of the layer on the object side to be νd₁ and the Abbe's number of the layer on the image face side to be νd₂, the following relation is satisfied: νd₁ < νd₂, or νd₁ > νd₂.
Claim 3
Dependent Claim
24 words
An optical low-pass filter according to Claim 1, wherein a striped phase difference generating portion is formed at the boundary between the two layers.
Claim 4
Dependent Claim
28 words
An optical low-pass filter according to Claim 1, wherein a section at the boundary between the two layers has a shape in which triangular waves are periodically arranged.
Claim 5
Dependent Claim
28 words
An optical low-pass filter according to Claim 1, wherein a section at the boundary between the two layers has a shape in which trapezoidal waves are periodically arranged.
Claim 6
Dependent Claim
23 words
An optical low-pass filter according to Claim 1, wherein the boundary between the two layers has a configuration for two-dimensionally generating phase differences.
Claim 7
Dependent Claim
74 words
An optical low-pass filter according to Claim 1, wherein at least two layers comprise a first layer, a second layer which is in contact with the first layer at a first boundary, and a third layer which is in contact with the second layer at a second boundary on an opposite side to the first boundary, and the first boundary and the second boundary have periodic shapes crossing in perpendicular directions to each other.
References Cited (Backward Citations)
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