Patent EP0720040A2 successfully refreshed from Google Patents.
EP0720040A2
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EP
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Illumination system and display device
Assignee: Sharp Corp
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Filing: 1995-12-29
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Granted: —
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Expires: 2015-12-29
Abstract
Abstract An illumination system comprises a polarization selective holographic element (18) comprising at least one optically anisotropic material arranged to separate light of a first polarization type from light of a second polarization type, and means (12, 20, 22, 26) for converting light of at least one of the first and second polarization types to light of a common polarization type. Where the polarization selective holographic element (18) separates two orthogonal components of plane polarized light from one another, the converting means may comprise a polarization rotator, for example a half wave plate (20), or alternatively a quarter wave plate (22) and a reflector (12, 26) arranged to reflect light back through the quarter wave plate (22). Where the polarization selective holographic element separates opposite handed components of circularly polarized light, the converting means may comprise a reflector (12, 26).
Inventors
- 👤 Gillian Davis
- 👤 Paul May
- 👤 Kathryn Walsh
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 08:49
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/133; G02F1/1333; G02F1/1335; G02F1/1336; G02F1/13362; G02F1/133528; G02F1/133536; G02F1/13363; G02F1/133631
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
78 words
An illumination system for a display device comprising a polarization selective element (18) arranged to separate light of a first polarization type from light of a second polarization type, and means (12, 20, 22, 26, 32) for converting light of at least one of the first and the second polarization type into light of a common polarization type, characterised in that the polarization selective element (18) is a holographic element (18) comprising at least one optically anisotropic material.
Claim 2
Dependent Claim
21 words
An illumination system as claimed in Claim 1, characterised in that the holographic element (18) is of thin, substantially planar form.
Claim 3
Dependent Claim
27 words
An illumination system as claimed in Claim 2, characterised in that the holographic element (18) is substantially parallel to the converting means (12, 20, 22, 26, 32).
Claim 4
Dependent Claim
40 words
An illumination system as claimed in any one of the preceding claims, characterised in that the converting means (12, 20, 22, 26, 32) is arranged to convert light of the second polarization type to light of the first polarization type.
Claim 5
Dependent Claim
34 words
An illumination system as claimed in any one of Claims 1 to 4, characterised in that the holographic element (18) is arranged to separate one type of elliptically polarized light from another type thereof.
Claim 6
Dependent Claim
29 words
An illumination system as claimed in Claim 5, characterised in that the holographic element (18) is arranged to separate one type of circularly polarized light from another type thereof.
Claim 7
Dependent Claim
35 words
An illumination system as claimed in any one of Claims 1 to 4, characterised in that the holographic element (18) is arranged to separate one type of plane polarized light from an orthogonal type thereof.
Claim 8
Dependent Claim
37 words
An illumination system as claimed in any one of the preceding claims, characterised in that the holographic element (18) is arranged to transmit light of the first polarization type and reflect light of the second polarization type.
Claim 9
Dependent Claim
28 words
An illumination system as claimed in Claim 8 when dependent upon Claim 5, characterised in that the converting means comprises a waveplate (22) and a reflector (12, 26).
Claim 10
Dependent Claim
24 words
An illumination system as claimed in Claim 8 when dependent upon Claim 6, characterised in that the converting means comprises a reflector (12, 26).
Claim 11
Dependent Claim
30 words
An illumination system as claimed in Claim 9 when dependent upon Claim 7, characterised in that the converting means comprises a quarter wave plate (22) and a reflector (12, 26).
Claim 12
Dependent Claim
52 words
An illumination system as claimed in any one of Claims 1 to 7, characterise in that the holographic element (18) is arranged to transmit light of the first polarization type in a first direction and to transmit light of the second polarization type in a second direction different from the first direction.
Claim 13
Dependent Claim
50 words
An illumination system as claimed in Claim 12 when dependent upon Claim 7, characterised in that the converting means comprises an array (20) of polarization rotators (20a) arranged to convert the light of at least one of the first and second polarization types into light of the common polarization type.
Claim 14
Dependent Claim
19 words
An illumination system as claimed in Claim 13, characterised in that the polarization rotators (20a) comprise half wave plates.
Claim 15
Dependent Claim
59 words
An illumination system as claimed in Claim 13 or Claim 14, characterised in that the array (20) of polarization rotators (20a) forms a patterned polarization rotator including first regions (20a) which convert light of the second polarization type to light of the first polarization type and second regions (20b) which do not affect the polarization of light incident thereon.
Claim 16
Dependent Claim
43 words
An illumination system as claimed in any one of Claims 12 to 15, characterised in that the holographic element (18) is arranged to transmit light of a first wavelength in the first direction and light of a second wavelength in the second direction.
Claim 17
Dependent Claim
39 words
An illumination system as claimed in Claim 16, characterised in that the holographic element (18) is arranged to transmit light of at least one further wavelength in at least one further direction different from the first and second directions.
Claim 18
Dependent Claim
27 words
An illumination system as claimed in any one of the preceding claims, characterised by a light source (10) arranged to emit light towards the holographic element (18).
Claim 19
Dependent Claim
22 words
An illumination system as claimed in Claim 18, characterised in that the light source (10) is arranged to emit substantially unpolarized light.
Claim 20
Dependent Claim
25 words
An illumination system as claimed in any one of the preceding claims, characterised in that the holographic element (18) comprises an optically induced birefringent polymer.
Claim 21
Dependent Claim
34 words
An illumination system as claimed in any one of Claims 1 to 19, characterised in that the holographic element (18) comprises a stack of birefringent layers of material other than optically induced birefringent polymer.
Claim 22
Dependent Claim
26 words
An illumination system as claimed in any one of Claims 1 to 19, characterised in that the holographic element (18) comprises a cross-linked liquid crystal polymer.
Claim 23
Dependent Claim
27 words
An illumination system as claimed in any one of Claims 1 to 11 and Claims 18 to 22, further comprising a patterned colour selective holographic element (32).
Claim 24
Dependent Claim
23 words
A display device characterised by an illumination system as claimed in any one of the preceding claims and a spatial light modulator (14).
Claim 25
Dependent Claim
30 words
A display device as claimed in Claim 24, when dependent on Claim 23, characterised in that the colour selective holographic element (32) is integral with the spatial light modulator (14).
Claim 26
Dependent Claim
24 words
A display device as claimed in Claim 24 or 25, characterised in that the spatial light modulator comprises a liquid crystal display device (14).
References Cited (Backward Citations)
US5062098A
Cited
JPH05181401A
Cited
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