EP0588937B1
Expired / Lapsed
EP
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Retroreflecting polarizer
Assignee: 3M Co
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Filing: 1992-05-20
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Granted: 1996-08-28
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Expires: 2012-05-20
Abstract
Abstract A retroreflecting polarizer (10), comprising optical thin films coated on a structured material (12, 14) divides an incident beam of light into polarized components (18-s, 18-p) transmitting one component (18-p) through the polarizer and reflecting the other (18-s) back to the source.
Inventors
- 👤 Michael F. Weber
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 13:12
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/30; G02B5/12; G02B5/122; G02B5/124; G02B5/3025; G02B5/3066
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
335 words
A retroreflecting polarizer (10; 100) comprising: a) a first layer (12) of a transparent flexible material having a smooth surface and an opposite structured surface, the structured surface consisting of a linear array of substantially right angled isosceles prisms arranged side by side and having sides which are perpendicular to each other and which make an angle of approximately 45° with respect to said smooth surface; b) a second layer (14) of a transparent flexible material configured essentially like the first layer, the structured surfaces of the first and second layers having substantially the same dimensions so that they can mate with each other; c) on the structured surface of at least one of said layers, at least one optical stack (16) of alternating thin layers (20, 22) of high and low refractive index materials; the first and second layers (12, 14) and said thin layers (20, 22) all optically cemented to form a single unit (10; 100) in which the structured surfaces face each other with the alternating thin layers (20, 22) positioned therebetween and in which the refractive index of the first and second layers (12, 14) and the refractive indices and optical thicknesses of the layers (20, 22) of the optical stack (16) are such that selective reflection of polarized light is produced so that: d) a light beam of mixed polarization (18; 118) incident on the unit from one side is separated by the optical stack (16) into an s-polarized component (18-s; 118-s) and a p-polarized component (18-p; 118-p), e) the s-polarized component is reflected from where the beam is incident on the optical stack onto another portion of the optical stack and there reflected parallel to the beam incident on the optical stack but propagating in the opposite direction so that this component leaves the unit in the direction opposite that of the beam incident on the unit, and f) the p-polarized component is transmitted through the unit and leaves the unit parallel to the beam incident on the unit.
Claim 2
Dependent Claim
23 words
The polarizer of claim 1 wherein the angle that said sides of said prisms make with respect to said smooth surface is 40°-50°.
Claim 3
Dependent Claim
52 words
The polarizer of claims 1 or 2, wherein the optical stack comprises at least two sub-stacks: a first sub-stack having a bandwidth centered on a first wavelength within the visible spectrum and a second sub-stack having a bandwidth centered on a second wavelength, different from the first wavelength, within the visible spectrum.
Claim 4
Dependent Claim
26 words
The polarizer of claim 3, wherein the optical stack further comprises a third sub-stack having a bandwidth centered on a third wavelength within the visible spectrum.
Claim 5
Dependent Claim
149 words
An optical system comprising, along a common optical axis: a) the retroreflecting polarizer (100) of claim 1; b) a display device (110) employing polarized light located adjacent the retroreflecting polarizer (100); c) a source of incident light of mixed polarization (118) located adjacent the retroreflecting polarizer (100) and opposite the display device (110); d) a reflector (130) located adjacent the light source and opposite the retroreflecting polarizer (100); and e) a quarterwave retardation plate (120) located between the reflector (130) and the retroreflecting polarizer (100), in which the p-polarized component (118-p) is transmitted to the display device (110), and the s-polarized component (118-s) is retroreflected from the retroreflecting polarizer (100), passes through the quarterwave retardation plate (120) to the reflector (130) where it is reflected back through the quarterwave retardation plate (120) a second time thereby becoming a second p-polarized component (121) before proceeding to the display device (110).
References Cited (Backward Citations)
No citation records indexed.
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