US3832038A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hand retroviewer
Assignee: 3M Co
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Filing: 1972-08-09
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Granted: 1974-08-27
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Expires: 1992-08-09
Abstract
Abstract A hand retroviewer for use in verifying a document having a retro-reflective image bearing layer which is substantially transparent under ordinary diffuse light viewing conditions to provide viewing of images on an underlying surface. The viewer housing has a viewing passageway therethrough and a beam splitter having a specular reflectance of at least 60 percent is mounted in the viewing passageway. A lamp and a condensing lens which combine to produce a virtual image of the light source that has an area less than .5 square inch are positioned to transmit light to the beam splitter. Light reflected from the beam splitter is retro-reflected from the image bearing layer of a document held spaced from the viewer along the illumination axis and a portion of the retro-reflected light is transmitted through the beam splitter for viewing to verify the document by its retroreflected image.
Inventors
- 👤 E Johnson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 18:47
CPC Classifications
G; G07; G07F; G07F7/00; G07F7/08; G07F7/086; G02; G02B; G02B27/00; G02B27/02; G02B27/022; G02B27/024; G02B27/025
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
199 words
A hand retroviewer for use in verifying a document under ambient lighting conditions typical of indoor illumination levels, said document having a retro-reflective image bearing layer which is substantially transparent under diffuse light viewing conditions, comprising: a housing formed with a body defining a handle and a head extending from said body, said head being formed with a viewing passageway therethrough, a lamp mounted in said housing to provide a light source, a condensing lens mounted in said housing and positioned to collect and transmit light from said lamp, said lamp and said lens combining to produce a virtual image of the light source that has an area less than 0.5 square inch, and a beam splitter mounted in saId viewing passage through said head inclined to the optical axis of said lamp and said lens to reflect through said viewing passageway a portion of the light transmitted by said lens and to transmit through said viewing passageway a portion of any light reflected by said beam splitter and thereafter retro-reflected from a said document, said beam splitter having a specular reflectance of at least 60 percent at the angle of incidence of light transmitted thereto by said lens.
Claim 2
Dependent Claim
199 words
A hand retroviewer for use in verifying a document under ambient lighting conditions typical of indoor illumination levels, said document having a retro-reflective image bearing layer which is substantially transparent under diffuse light viewing conditions, comprising: a housing formed with a body defining a handle and a head extending from said body, said head being formed with a viewing passageway therethrough, a lamp mounted in said housing to provide a light source, a condensing lens mounted in said housing and positioned to collect and transmit light from said lamp, said lamp and said lens combining to produce a virtual image of the light source that has an area less than 0.5 square inch, and a beam splitter mounted in saId viewing passage through said head inclined to the optical axis of said lamp and said lens to reflect through said viewing passageway a portion of the light transmitted by said lens and to transmit through said viewing passageway a portion of any light reflected by said beam splitter and thereafter retro-reflected from a said document, said beam splitter having a specular reflectance of at least 60 percent at the angle of incidence of light transmitted thereto by said lens.
Claim 3
Dependent Claim
36 words
The hand retroviewer of claim 1 including an eyepiece secured to said head of said housing over one end of said viewing passageway therethrough for positioning the eye of a user at a predetermined viewing position.
Claim 4
Dependent Claim
49 words
The hand retroviewer of claim 2 wherein said eyepiece is secured to said head to position the eye of a user along a viewing axis at an angle of divergence from the illumination axis defined by said lamp, said lens and said beam splitter of from 0.2* to 2*.
Claim 5
Dependent Claim
14 words
The hand retroviewer of claim 3 wherein said divergence angle is 0.4* to 0.6*.
Claim 6
Dependent Claim
32 words
The hand retroviewer of claim 4 wherein the viewing position defined by said eyepiece is spaced the same distance from said beam splitter as is the virtual image of the light source.
Claim 7
Dependent Claim
32 words
The hand retroviewer of claim 2 wherein the viewing position defined by said eyepiece is spaced the same distance from said beam splitter as is the virtual image of the light source.
Claim 8
Dependent Claim
17 words
The hand retroviewer of claim 6 wherein the speed of said condensing lens is greater than f/2.
Claim 9
Dependent Claim
21 words
The hand retroviewer of claim 7 including a source of electrical energy for said lamp in said body of said housing.
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) | 1977-08-26 | 1978-02-25 | 1978-08-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-26 | 1982-02-25 | 1982-08-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-26 | 1986-02-25 | 1986-08-27 | $7700.00 | Window Closed / Lapsed |