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EP0759573A2
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EP
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Wavelength-selective phase-type optical low-antialiasing filter and fabrication methods
Assignee: Eastman Kodak Co
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Filing: 1996-08-05
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Granted: —
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Expires: 2016-08-05
Abstract
Abstract A wavelength-selective optical low-pass filter for use with an optical imaging system of a solid-state color imager, comprising a transparent substrate and a plurality of transparent spots randomly placed on the substrate for producing a phase difference between a wavefront transmitted through the spots and that portion of the substrate other than the spots to define a filter having a spatial sampling cut-off frequency which varies depending on wavelength of light, the phase difference satisfying the following conditions cosφ α = 1 -1.0 ≤ cosφ β ≤ -0.4 -1.0 ≤ cosφ γ ≤ -0.4 where φ α , φ β , and φ γ are the phase differences due to the spots at certain specific wavelengths in the visible through infrared portion of the optical spectrum, and are given by the following relationship φ i = 2π n i - n i ' λ i t where i = α, β, or γ; n i ; is the index of refraction of the material comprising the spots at the specific wavelength λ i ; n i ' is the index of refraction of the medium surrounding the spots at the specific wavelength λ i ; and t is the physical thickness of the spots.
Inventors
- 👤 Joseph F. Jr. c/o Eastman Kodak Co. Revelli
- 👤 Alan C.G. c/o Eastman Kodak Co. Nutt
- 👤 Eric T. c/o Eastman Kodak Co. Prince
- 👤 John c/o Eastman Kodak Co. Gasper
- 👤 Sharlene A. c/o Eastman Kodak Co. Wilson
- 👤 Todd A. c/o Eastman Kodak Co. Jackson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 11:53
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/18; G02B5/1866; G02B5/1871; G02B27/00; G02B27/42; G02B27/46
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
203 words
A wavelength-selective optical low-pass filter for use with an optical imaging system of a solid-state color imager, comprising a transparent substrate and a plurality of transparent spots randomly placed on the substrate for producing a phase difference between a wavefront transmitted through the spots and that portion of the substrate other than the spots to define a filter having a spatial sampling cut-off frequency which varies depending on wavelength of light, the phase difference satisfying the following conditions cosφ α = 1 -1.0 ≤ cosφ β ≤ -0.4 -1.0 ≤ cosφ γ ≤ -0.4 where φ α , φ β , and φ γ are the phase differences due to the spots at certain specific wavelengths in the visible through infrared portion of the optical spectrum, and are given by the following relationship φ i = 2π n i - n i ' λ i t where i = α, β, or γ; n i is the index of refraction of the material comprising the spots at the specific wavelength λ i ; n i ' is the index of refraction of the medium surrounding the spots at the specific wavelength λ i ; and t is the physical thickness of the spots.
Claim 2
Independent Claim
104 words
A method of forming a wavelength-selective optical low-pass filter for use with an optical imaging system of a solid-state color imager, comprising the steps of: a) preparing a mold having on its surface a relief pattern which is the inverse of the randomly placed transparent spots, the depth of the relief being equal to the thickness of the randomly placed transparent spots plus any tooling factor, if applicable; and b) using the mold to stamp, extrude, or otherwise form replicates in an organic polymer of the low-pass optical filter comprising a transparent substrate and a plurality of transparent spots randomly placed on the substrate.
Claim 3
Independent Claim
182 words
A method of forming a wavelength-selective optical low-pass filter for use with an optical imaging system of a solid-state color imager, comprising the steps of: a) coating a transparent glass wafer with a layer of transparent organic polymer material having a thickness that is equal to the thickness of the randomly placed transparent spots; b) forming a thin etch-stop layer on the transparent organic polymer layer; c) coating a thin layer of photoresist to form a mask on the thin etch-stop layer and patterning the photoresist so that the pattern corresponds to the randomly placed transparent spots to be formed; d) transferring the mask pattern of the randomly placed transparent spots in the photoresist to the thin etch-stop layer by wet or dry etching techniques; e) anisotropically dry etching ( e.g., using oxygen reactive ion or plasma) transparent organic polymer layer according to the thin etch-stop mask pattern; and f) removing the thin etch-stop layer using wet or dry etching techniques thereby forming the low-pass optical filter comprising a transparent substrate and a plurality of transparent spots randomly placed on the substrate.
Claim 4
Dependent Claim
38 words
The method of claim 15 wherein the transparent organic polymer is selected from the group consisting of: polyacrylates or methacrylates; polycarbonates; polyester; polyolefins; polystyrenes; polyimides; polyurethanes; polyethers; polyamides; polysulphones; and evaporated or spun-on low molecular weight organic glasses.
Claim 5
Dependent Claim
25 words
The method of claim 15 wherein the thin etch-stop is an inorganic material such as silicon dioxide, silicon nitride, silicon, germanium, titanium, or organometallic glasses.
Claim 6
Dependent Claim
24 words
The method of claim 17 wherein the etch-stop layers are deposited by RF sputtering, thermal evaporation, plasma-enhanced chemical vapor deposition, or spin-on glass techniques.
Claim 7
Independent Claim
229 words
A method of forming a wavelength-selective optical low-pass filter for use with an optical imaging system of a solid-state color imager, comprising the steps of: a) providing a first thin RIE etch-stop layer on a transparent glass substrate; b) coating a thick layer of transparent glass on the first thin RIE etch-stop layer, the thick deposited transparent glass layer having an optical thickness that is equal to the optical thickness of the randomly placed transparent spots less the optical thickness of the first thin RIE etch-stop layer, the optical thickness being defined as the index of refraction of a layer times the physical thickness of the layer; c) providing a second thin RIE etch-stop layer on the thick layer of deposited transparent glass and patterning a thin photoresist mask on the second thin RIE etch-stop layer so that the pattern corresponds to the randomly placed transparent spots to be formed; d) transferring by methane etching the pattern of the randomly placed transparent spots in the photoresist mask to the second thin RIE etch-stop layer; e) anisotropically dry etching ( e.g., using a freon reactive ion or plasma etch) thick deposited transparent glass layer according to the second thin RIE etch-stop mask pattern; f) removing the remaining portions of the photoresist mask; and g) removing by methane etching the exposed portions of the first and the second thin etch-stop layers.
Claim 8
Dependent Claim
36 words
The method of claim 19 wherein the thick deposited transparent glass layer is silicon dioxide or some other inorganic glass and is coated by chemical vapor deposition, spin on glass techniques, or some other similar method.
Claim 9
Dependent Claim
35 words
The method of claim 19 wherein the thin RIE etch-stop layer is an inorganic material such as indium tin oxide (ITO), SnO 2 , In 2 O 3 , or Al 2 O 3 .
Claim 10
Dependent Claim
26 words
The method of claim 21 wherein the first and second RIE etch-stop layers are deposited by RF sputtering, thermal evaporation, or plasma enhanced chemical vapor deposition.
Claim 11
Independent Claim
204 words
A method of forming a wavelength-selective optical low-pass filter for use with an optical imaging system of a solid-state color imager, comprising the steps of: a) providing a thin ion-exchange masking layer on a suitable transparent glass substrate the glass substrate containing one or more ionic species which can be exchanged and patterning a thin photoresist mask on the thin ion-exchange masking layer so that the pattern corresponds to the randomly placed transparent spots to be formed; b) transferring by wet etching the pattern of the randomly placed transparent spots in the photoresist mask to the thin ion-exchange masking layer to form the ion-exchange mask; c) removing the photoresist mask pattern and submerging the masked transparent glass substrate into a bath containing molten salts of one or more ionic species which are different from the ionic species present in the masked transparent glass substrate; and d) removing the masked transparent glass substrate from the bath after a period of time which permits exchange of the ionic species in the bath and the ionic species present in the masked transparent glass substrate in those regions where the surface of the transparent glass substrate comes into direct contact with said bath and removing said ion-exchange mask.
References Cited (Backward Citations)
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