High contrast light shutter system
First Claim
1. A high contrast light shutter system that produces opaque and transmissive states corresponding to respective first and second states of a variable optical retarder, comprising:
- variable optical retarder means for selectively providing a nonzero residual amount of retardation in the first state and an increased amount of optical retardation equal to the sum of the residual amount and half-wave retardation in the second state, the variable optical retarder having an optical thickness corresponding to the increased amount of retardation in the second state; and
first and second polarizing means between which the variable optical retarder means is positioned for polarizing light incident to them, the first polarizing means including a fixed optical retarder and a linear polarizer that cooperate to compensate for the effect of the residual amount of retardation present in both states of the variable retarder so as to maximize and minimize light transmission in the respective transmissive and opaque states.
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Accused Products
Abstract
A light shutter system (10) incorporates a liquid crystal cell (12) operating as a variable optical retarder to selectively produce opaque and transmissive optical states corresponding to the respective first and second amounts of optical retardation of the variable optical retarder. The cell switches between a residual amount of retardation and an increased amount that equals the sum of half-wave retardation and the amount of residual retardation to provide a shutter system whose system retardation switches between zero retardation and half-wave retardation and thereby produces opaque and transmissive states with an optimal contrast ratio. The cell is positioned between a linear polarizing filter (14) and an elliptical analyzer (16), the latter including a linear polarizing filter (20) and an optical retarder (18) of fixed value. The transmission axis of the linear polarizing filters are angularly displaced relative to a projection of the optic axes of the cell by an amount that provides maximum light extinction in the opaque state. Maximum output light transmissive in the transmission state is achieved by establishing for the cell an optical thickness that exceeds half-wave retardation by an additional amount equal to the residual retardation. Other preferred embodiments that provide equivalent performance are described.
149 Citations
10 Claims
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1. A high contrast light shutter system that produces opaque and transmissive states corresponding to respective first and second states of a variable optical retarder, comprising:
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variable optical retarder means for selectively providing a nonzero residual amount of retardation in the first state and an increased amount of optical retardation equal to the sum of the residual amount and half-wave retardation in the second state, the variable optical retarder having an optical thickness corresponding to the increased amount of retardation in the second state; and first and second polarizing means between which the variable optical retarder means is positioned for polarizing light incident to them, the first polarizing means including a fixed optical retarder and a linear polarizer that cooperate to compensate for the effect of the residual amount of retardation present in both states of the variable retarder so as to maximize and minimize light transmission in the respective transmissive and opaque states. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification