RETROVIEWER
First Claim
1. A retroviewer for use in verifying a document having a retroreflective image bearing layer which is substantially transparent under diffuse light viewing conditions, comprising:
- a housing, a lamp mounted in said housing to provide a light source, a condensing lens positioned to collect and transmit light from said lamp, a viewing stage for supporting a said document to be verified, a beam splitter inclined to the optical axis of said lamp and lens and positioned to reflect onto said viewing stage a portion of the light transmitted by said lens and to transmit a portion of any light retro-reflected from a said document on said stage, said lamp and said condensing lens combining to produce a virtual image of the light source that has an area between 0.5 sq. in. and 3 sq. in.
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Accused Products
Abstract
A retroviewer for use in verifying a document having a retroreflective image bearing layer which is substantially transparent under ordinary diffuse light viewing conditions to provide viewing of images on an underlying surface. The viewer includes a lamp and a condensing lens mounted in a housing and in combination producing a virtual image of the light source that has an area between 0.5 sq. in. and 3 sq. in. A beam splitter is inclined to the optical axis of the lamp and condenser lens combination and it is positioned to reflect a portion of the light transmitted by the lens onto a viewing stage which supports a document to be verified. Light reflected from the beam splitter is retro-reflected from the image bearing layer of the document and a portion thereof is transmitted through the beam splitter for viewing to verify the document by its retro-reflective image.
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Citations
7 Claims
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1. A retroviewer for use in verifying a document having a retroreflective image bearing layer which is substantially transparent under diffuse light viewing conditions, comprising:
- a housing, a lamp mounted in said housing to provide a light source, a condensing lens positioned to collect and transmit light from said lamp, a viewing stage for supporting a said document to be verified, a beam splitter inclined to the optical axis of said lamp and lens and positioned to reflect onto said viewing stage a portion of the light transmitted by said lens and to transmit a portion of any light retro-reflected from a said document on said stage, said lamp and said condensing lens combining to produce a virtual image of the light source that has an area between 0.5 sq. in. and 3 sq. in.
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2. A retroviewer as recited in claim 1 wherein said lamp and said condensing lens combine to produce a virtual image of the light source that is between 0.8 sq. in. and 2 sq. in.
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3. A retroviewer as recited in claim 1 wherein said lamp and said condensing lens combine to produce a virtual image of the light source that is spaced from said viewing stage a distance of from 14 to 18 inches.
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4. A retroviewer as recited in claim 1 wherein said condensing lens has a focal length less than 5 in.
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5. A retroviewer as recited in claim 1 wherein said lamp has a filament defining said light source said lamp being positioned with the longest dimension of said filament perpendicular to the optical axis of said lamp and lens to illuminate a rectangular area on said viewing stage.
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6. A retroviewer for use in verifying a document having a retro-reflective image bearing layer which is substantially transparent under diffuse light viewing conditions, comprising:
- a housing, a lamp mounted in said housing to provide a light source, a condensing lens positioned to collect and transmit light from said lamp, a viewing stage for supporting a said document to be verified, a beam splitter inclined to the optical axis of said lamp and lens and positioned to reflect onto said viewing stage a portion of the light transmitted by said lens and to transmit a portion of any light retro-reflected from a said document on said stage, said lamp and said condensing lens combining to produce a virtual image of the light source sufficiently large that the line of sight to each part of a predetermined document area on said viewing stage passes through the retro-image of the virtual image of the light source over a range of distances from said viewing stage along the optical viewing axis from at least 25 percent of the retro-image to viewing stage distance below the retro-image to at least 50 percent of the retro-image to viewing stage distance above the retro-image and sufficiently small that the retro-luminance of the retro-reflective layer of a properly validated document is high enough to obscure any images underlying the retro-reflective layer.
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7. A retroviewer for use in verifying a document having a retro-reflective image bearing layer which is substantially transparent under diffuse light viewing conditions, comprising:
- a housing, a lamp mounted in said housing to provide a light source, a condensing lens positioned to collect and transmit light from said lamp, a viewing stage for supporting a said document to be verified, a beam splitter inclined to the optical axis of said lamp and lens and positioned to reflect onto said viewing stage a portion of the light transmitted by said lens and to transmit a portion of any light retro-reflected from a said document on said stage, said lamp and said condensing lens combining to produce a virtual image of the light source sufficiently large that the line of sight to all parts of a predetermined document area on said viewing stage pass through the retro-image of the virtual image of the light source over a range of distances along the optical viewing axis of at least ten inches and sufficiently small that the retro-luminance of the retro-reflective layer of a properly validated document is high enough to obscure any images underlying said retro-reflective layer.
Specification