Optical diffusers, photomasks and their methods of fabrication
First Claim
1. A photomask comprising:
- a mask having a plurality of cell mask areas, the cell mask areas disposed in an XY matrix;
wherein all of the cell mask areas have a substantially identical pattern of randomly placed transmissive apertures, and the photomask, viewed as a whole, appears macroscopically uniform and without an apparent grid pattern.
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Accused Products
Abstract
A large mask with random apertures may be formed by forming a smaller mask (also called a cell mask) with a random pattern of transmissive apertures which is then repeatedly replicated to create the large mask. The random pattern may be created by perturbing the aperture locations by a small amount or the apertures may be randomly placed within the cell mask provided certain criteria are met. Alternatively, a large mask with a random pattern of transmissive apertures may be formed without using a cell mask. This large mask may be used to fabricate diffusers and other devices that do not suffer from the interference, diffraction and other optical effects common in devices having structures that are non-randomly patterned.
41 Citations
19 Claims
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1. A photomask comprising:
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a mask having a plurality of cell mask areas, the cell mask areas disposed in an XY matrix; wherein all of the cell mask areas have a substantially identical pattern of randomly placed transmissive apertures, and the photomask, viewed as a whole, appears macroscopically uniform and without an apparent grid pattern. - View Dependent Claims (2, 3, 4, 5, 11)
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6. A method of fabricating a photomask comprising:
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generating a plurality of cell mask areas, each cell mask area having transmissive apertures, all of the cell mask areas having a substantially identical pattern of randomly placed transmissive apertures; positioning the generated cell mask areas in an XY matrix; and forming the transmissive apertures patterns in the photomask; wherein the photomask, viewed as a whole, appears macroscopically uniform and without an apparent grid pattern. - View Dependent Claims (7, 8, 9, 10)
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12. A method of fabricating a photomask comprising the steps of:
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a) generating a cell mask area having a pattern of transmissive apertures randomly placed, each transmissive aperture having a center; b) removing a transmissive aperture from the cell mask area if the transmissive aperture is spaced from adjacent transmissive apertures by less than a minimum amount; c) removing a transmissive aperture from the cell mask area if the transmissive aperture is not spaced from transmissive apertures along opposing boundaries of the cell mask area by at least the minimum amount; and d) forming the pattern of transmissive apertures in the photomask; wherein the photomask, viewed as a whole, appears macroscopically uniform. - View Dependent Claims (13, 14)
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15. A method of fabricating a photomask comprising the steps of:
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a) generating a cell mask area having a pattern of transmissive apertures randomly placed, each transmissive aperture having a center; b) removing a transmissive aperture from the cell mask area if the transmissive aperture is spaced from adjacent transmissive apertures by less than a minimum amount; c) replicating the cell mask area and placing the replicated cell mask areas in an XY matrix; d) removing a transmissive aperture from at least one cell mask area if the transmissive aperture is spaced from transmissive apertures in adjacent cell mask areas and opposing cell mask areas, if any, by less than the minimum amount; and e) forming the pattern of transmissive apertures in the photomask; wherein the photomask, viewed as a whole, appears macroscopically uniform. - View Dependent Claims (16, 17, 18, 19)
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Specification