GB1426605A - Retroviewer - Google Patents

Retroviewer

Info

Publication number
GB1426605A
GB1426605A GB3314373A GB3314373A GB1426605A GB 1426605 A GB1426605 A GB 1426605A GB 3314373 A GB3314373 A GB 3314373A GB 3314373 A GB3314373 A GB 3314373A GB 1426605 A GB1426605 A GB 1426605A
Authority
GB
United Kingdom
Prior art keywords
retro
document
layer
light
reflective
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB3314373A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Co
Original Assignee
Minnesota Mining and Manufacturing Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Minnesota Mining and Manufacturing Co filed Critical Minnesota Mining and Manufacturing Co
Priority to GB3314373A priority Critical patent/GB1426605A/en
Publication of GB1426605A publication Critical patent/GB1426605A/en
Expired legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/02—Viewing or reading apparatus
    • G02B27/022—Viewing apparatus
    • G02B27/024—Viewing apparatus comprising a light source, e.g. for viewing photographic slides, X-ray transparancies

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Elements Other Than Lenses (AREA)

Abstract

1426605 Retroviewer MINNESOTA MINING AND MFG CO 11 July 1973 33143/73 Heading G2J A retro-viewer for verifying a document 20 having a retro-reflective image bearing layer comprises a condenser, e.g. Fresnel lens 14, collecting light from a light source e.g. lamp 12 and a beamsplitter 16 reflecting light from the condenser on to the document on stage 18 and transmitting retro-reflective light from the layer on the document through e.g. transparent plate 22 to an observer, the condenser producing a virtual image of the light source sufficiently large that the observer's line of sight to all parts of a predetermined document area on the stage passes through the retro-image of the virtual image of the light source over a predetermined range of distances along the optical viewing axis, and sufficiently small that the retro-luminance of the retro-reflective layer is high enough to obscure images on the document underlying the layer. Thus when e.g. an identity card carrying information and having verifying legends on a retro-reflective layer is moved through a slot on to the stage, a lamp switch is actuated by the card and the observer sees only the legends, whereas in normal diffuse light, the layer is transparent and only the information on the card is seen.
GB3314373A 1973-07-11 1973-07-11 Retroviewer Expired GB1426605A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB3314373A GB1426605A (en) 1973-07-11 1973-07-11 Retroviewer

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3314373A GB1426605A (en) 1973-07-11 1973-07-11 Retroviewer

Publications (1)

Publication Number Publication Date
GB1426605A true GB1426605A (en) 1976-03-03

Family

ID=10349111

Family Applications (1)

Application Number Title Priority Date Filing Date
GB3314373A Expired GB1426605A (en) 1973-07-11 1973-07-11 Retroviewer

Country Status (1)

Country Link
GB (1) GB1426605A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5751412A (en) * 1993-11-05 1998-05-12 Mikoh Technology Limited Diffraction viewing device to aid in authenticating an optical surface

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5751412A (en) * 1993-11-05 1998-05-12 Mikoh Technology Limited Diffraction viewing device to aid in authenticating an optical surface

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Legal Events

Date Code Title Description
PS Patent sealed
732 Registration of transactions, instruments or events in the register (sect. 32/1977)
PCNP Patent ceased through non-payment of renewal fee