Switchable color filter with enhanced transmissivity
First Claim
1. A highly transmissive switchable color filter that receives light having color components within first and second color bands, comprising:
- polarizing means for polarizing light within the first and second color bands;
first and second color selective light-reflecting elements, the first light-reflecting element reflecting light within the first color band and in a first polarization state and the second light-reflecting element reflecting light within the second color band and in a second polarization state;
a light modulator positioned between the polarizing means and the first and second light-reflecting elements, the light modulator being operable to change the polarization state of light passing through it; and
switching means in communication with the light modulator for selectively providing first and second switching states, the first switching state causing light within the first color band to exit the color filter and blocking substantially all of the light within the second color band from exiting the color filter, and the second switching state causing light within the second color band to exit the color filter and blocking substantially all of the light within the first color band from exiting the color filter.
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Accused Products
Abstract
A switchable color filter employs chiral liquid crystal circular polarizers to minimize the attenuation of light passing through a system in which it is incorporated. One preferred embodiment (12) of the switchable color filter includes a light modulator (32) positioned between the light polarizing assembly (20) and first and second chiral liquid crystal cells (36 and 38). The light polarizing assembly receives unpolarized light and transmits circularly polarized light of colors included within first and second narrow color bands. The first chiral cell reflects incident light within the first color band and in a first polarization state, and the second chiral cell reflects incident light within the second color band and in a second polarization state. The light modulator cooperates with a switching circuit (34) to selectively provide first and second polarization switching states. The first switching state causes light within the first color band to exit the color filter and blocks light within the second color band from exiting the color filter, and the second switching state causes light within the second color band to exit the color filter and block light within the first color band from exiting the color filter. Another preferred embodiment (100) of the switchable color filter is capable of receiving light within three color bands and selectively providing a light output of one of three colors. Either embodiment of the switchable color filter can be advantageously implemented in systems (10 and 100) that are insensitive to a restricted viewing angle, which stems from the use of chiral liquid crystal circular polarizers.
84 Citations
20 Claims
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1. A highly transmissive switchable color filter that receives light having color components within first and second color bands, comprising:
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polarizing means for polarizing light within the first and second color bands; first and second color selective light-reflecting elements, the first light-reflecting element reflecting light within the first color band and in a first polarization state and the second light-reflecting element reflecting light within the second color band and in a second polarization state; a light modulator positioned between the polarizing means and the first and second light-reflecting elements, the light modulator being operable to change the polarization state of light passing through it; and switching means in communication with the light modulator for selectively providing first and second switching states, the first switching state causing light within the first color band to exit the color filter and blocking substantially all of the light within the second color band from exiting the color filter, and the second switching state causing light within the second color band to exit the color filter and blocking substantially all of the light within the first color band from exiting the color filter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A highly transmissive switchable color filter that receives light having color components within first, second, and third color bands, comprising:
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polarizing means for polarizing light within the first, second, and third color bands; a first light modulating section including a first light modulator and first and second color selective light-reflecting elements, the first light modulator being positioned between the polarizing means and the first and second light-reflecting elements and being operable to change the polarization state of light passing through it, the first light-reflecting element reflecting light within a first color band and in a first polarization state and the second light-reflecting element reflecting light within a second color band and in a second polarization state; a second light modulating section positioned adjacent the first light modulating section and including a second light modulator and third and fourth color selective light-reflecting elements, the second light modulator being positioned between the second and third light-reflecting elements and being operable to change the polarization state of light passing through it, the third light-reflecting element reflecting light within a third color band and in the first polarization state and the fourth light-reflecting element reflecting light within one of the first, second, and third color bands and in the second polarization state; and switching means in communication with the first and second light modulators for selectively providing first, second, and third switching states, the first switching state causing light within the first color band to exit the color filter and blocking substantially all of the light in the second and third color bands from exiting the color filter, the second switching state causing light within the second color band to exit the color filter and blocking substantially all of the light within the first and third color bands from exiting the color filter, and the third switching state causing light within the third color band to exit the color filter and blocking substantially all of the light within the first and second color bands from exiting the color filter. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification