US3767291A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Retroviewer
Assignee: 3M Co
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Filing: 1972-03-31
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Granted: 1973-10-23
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Expires: 1992-03-31
Abstract
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.
Inventors
- 👤 E Johnson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 13:04
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/02; G02B27/022; G02B27/024; G02B27/025
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
134 words
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.
Claim 2
Dependent Claim
134 words
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.
Claim 3
Dependent Claim
34 words
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.
Claim 4
Dependent Claim
39 words
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.
Claim 5
Dependent Claim
19 words
A retroviewer as recited in claim 1 wherein said condensing lens has a focal length less than 5 in.
Claim 6
Dependent Claim
47 words
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.
Claim 7
Dependent Claim
223 words
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.
Claim 8
Dependent Claim
223 words
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.
Claim 9
Dependent Claim
194 words
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.
Claim 10
Dependent Claim
194 words
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.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-22 | 1977-04-23 | 1977-10-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-22 | 1981-04-23 | 1981-10-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-22 | 1985-04-23 | 1985-10-23 | $7700.00 | Window Closed / Lapsed |