EP0052000A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Variable colour filters
Assignee: Polaroid Corp
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Filing: 1981-11-06
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Granted: —
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Expires: 2001-11-06
Abstract
Abstract A variable colourfilter 10 comprises a plurality of differently coloured dichroic polarisers 12, 20 and 24, twisted numatic liquid crystal cells or other angle varying means 14, 18 and 22, and a plane polariser 16 all arranged along an optical path OA. By varying the angle varying means it is possible to modify the spectral content of visible light and transmit preselected colours through the filter.
Inventors
- 👤 William Torsch Plummer
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 03:47
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/133; G02F1/1333; G02F1/1347; G02F1/13471; G02F1/13473; G02F1/03; G02F1/1335; G02F1/133528; G02F1/133533; G02F1/137; G02F1/139; G02F1/1396
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
152 words
A filter for varying the spectral composition of visible light and comprising a plurality of optical elements stationed along the optical path of the light and characterised in that the elements include a plurality of differently coloured dye polarising elements each of which plane polarises a different part of the visible spectrum while transmitting the remainder of the visible spectrum unpolarised, at least one angle varying means associated with each of the dye polarising elements for selectively varying the angle of the plane of the linearly polarised light, and a plane polariser for polarising substantially uniformly all wave lengths of the visible spectrum, the dye polarising elements, the plane polariser, and the angle varying means being arranged to permit the spectral content of visible light to be modified so that the filter transmits a preselected colour the saturation and hue of which is related to the operation of the angle varying means.
Claim 2
Dependent Claim
152 words
A filter for varying the spectral composition of visible light and comprising a plurality of optical elements stationed along the optical path of the light and characterised in that the elements include a plurality of differently coloured dye polarising elements each of which plane polarises a different part of the visible spectrum while transmitting the remainder of the visible spectrum unpolarised, at least one angle varying means associated with each of the dye polarising elements for selectively varying the angle of the plane of the linearly polarised light, and a plane polariser for polarising substantially uniformly all wave lengths of the visible spectrum, the dye polarising elements, the plane polariser, and the angle varying means being arranged to permit the spectral content of visible light to be modified so that the filter transmits a preselected colour the saturation and hue of which is related to the operation of the angle varying means.
Claim 3
Dependent Claim
35 words
A filter according to claim 1 characterised in that the dye polarising elements and the plane polariser are positioned with respect to one another with their polarising transmission axes at angular increments of 90° azimuth.
Claim 4
Dependent Claim
77 words
A filter according to claim I or claim 2 characterised in that there are three dye polarising elements one of which includes a magenta dye and plane polarises green light while transmitting red and blue light unpolarised, one of which includes a cyan dye and plane polarises red light while transmitting blue and green light unpolarised, and the third of which includes a yellow dye and plane polarises blue light while transmitting green and red light unpolarised.
Claim 5
Dependent Claim
92 words
A filter according to claim 3 characterised in that each dye polarising element is arranged with respect to the plane polariser so that any one of the dye polarisers in combination with the plane polariser transmits the entire visible spectrum when the plane of polarisation of the light absorbed by the dye polariser is parallel to the transmission axis of the plane polariser and transmits its designated colour by absorbing the complement thereof when the plane of polarisation of the absorbed light is crossed with the transmission axis of the plane polariser.
Claim 6
Dependent Claim
57 words
A filter according to claim 3 or claim 4 characterised by the following spatial arrangement along the optical path, namely the magenta dye polarising element, at least one angle varying means, the plane polariser, at least one angle varying means, the cyan dye polarising element, at least one angle varying means, and the yellow dye polarising element.
Claim 7
Dependent Claim
45 words
A filter according to any preceding claim characterised in that each angle varying means comprises a twisted nematic liquid crystal element connected to a selectively variable voltage source and provides angles of light transmissivity variable between 0 and 90° in accordance with the voltage applied.
Claim 8
Dependent Claim
34 words
A filter according to claim 6 characterised in that the dye polarisers and the twisted nematic liquid crystals are arranged as adjacent pairs and the plane polariser is positioned intermediate two of the pairs.
Claim 9
Dependent Claim
47 words
A filter according to claim 7 characterised in that each of the twisted nematic liquid crystals is arranged to cause a 90 rotation of the plane of polarisation for the entire spectrum when not fully energised, and when fully energised to transmit plane polarised light without rotation.
Claim 10
Dependent Claim
57 words
A filter according to any of claims 6 to 8 characterised in that one of the dye polarising elements is associated with two of the twisted nematic liquid crystals arranged together to give angles of light transmissivity varying between 0 and 180°, and the other dye polarising elements are each associated with one twisted nematic liquid crystal.
Claim 11
Dependent Claim
26 words
A filter according to any of claims 6 to 9 characterised in that the liquid crystals are constructed to selectively transmit predetermined colours in alphanumeric form.
Claim 12
Dependent Claim
22 words
A filter according to any of claims 1 to 5 characterised in that the angle varying means comprise rotatively mounted halfwave plates.
Claim 13
Dependent Claim
41 words
A filter according to any preceding claim characterised in that it additionally includes a mirror positioned at one end thereof such that light transmitted through the filter is reflected, at least a portion of the light being retroreflected through the filter.
References Cited (Backward Citations)
No citation records indexed.
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