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AssigneeAsulab S.A.
InventorsJoachim Grupp, Peter Kipfer, Toralf Scharf, Christian Bohley, Rolf Klappert, Hans Peter Herzig
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An optical device (20) is provided using at least one film (23) of cholesteric liquid crystal to reflect at least one predetermined wavelength band from an incident light. This device is characterized in that a non zero birefringence gradient is present in a portion or the entire thickness of said film. The gradient may be obtained in particular by superposing layers (24a-24j) having increasing or decreasing respective birefringence coefficients. The birefringence gradient has the effect of removing the lateral bands of the reflection spectrum, hence making the color of the reflected light more brilliant and more saturated. The effect is particularly advantageous in the case of the color red, for which the lateral band located on the yellow side is perceived strongly by the human eye.
A Bragg reflection optical device for reflecting at least one predetermined wavelength band present in an incident light, the device including at least one film of cholesteric type liquid crystal, wherein said liquid crystal film has, in at least a portion of its thickness, a birefringence gradient as a function of the depth in said film.
A method for manufacturinga Bragg reflection optical device for reflecting at least one predetermined wavelength band present in an incident light, the device including a film formed of a plurality of polymerised layers of cholesteric type liquid crystal,
A method for manufacturing a Bragg reflection optical device for reflecting at least one predetermined wavelength band present in an incident light,
Dependencies are inferred from the claim text.