Optical: systems and elements – Holographic system or element – Using a hologram as an optical element
Patent
1992-05-15
1993-07-27
Sikes, William L.
Optical: systems and elements
Holographic system or element
Using a hologram as an optical element
359 53, 359 56, 359 73, 359 63, 359100, G02F 1133
Patent
active
052315215
ABSTRACT:
The present invention provides optical polarization interference filters which employ chiral smectic liquid crystal (CSLC) cells as electronically rotatable retarders. The filters of the present invention are improved in that they are optimized for increased spectral discrimination, uniqueness of spectral outputs and efficient use of CSLC elements. The filters of the present invention include improved single and multiple stage filters. Improved discretely tunable and continuously tunable filters are provided. With respect to filters having one or more stages that contain a series of birefringent elements which are either fixed birefringent elements or active CSLC cells, this invention provides designs which optimize the number of pure spectral outputs which are unique. This optimization relates to the relative order of elements in a stage, the pattern of switching of the active CSLC cells, and the retardations of the CSLC cells in a stage. In a specific embodiment, this invention provides an improved tunable filter that substantially retains the transmissions of a Lyot-type multiple stage filter without requiring the thicknesses of the active CSLC cells to increase geometrically. Continuously tunable filters of this invention include those having a stage which has an analog variable retarder which is the combination of an achromatic quarter-waveplate and one or more analog CSLC cells in series.
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Johnson Kristina M.
Sharp Gary D.
Mai Huy K.
Sikes William L.
The University of Colorado Foundation Inc.
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