US 5,221,982 A · Polarizing wavelength separator

Abstract

A polarizing wavelength separating optical element, PWS, in the form of a flat panel causes each of a plurality of polychromatic optical beams from a source, entering at one surface and transmitted to the other surface, to be converted with high conversion efficiency into beams circularly polarized, spectrally separated and spatially separated. The input optical beams are identical and in the form of a linear periodic array illuminating the PWS element. Output circularly polarized beams are spatially separated by a variable distance and have separated wavelengths that can be in any order: ascending, descending or random. The PWS is made of a periodic array of cells whose period is identical to that of the optical source. Each cell comprises a plurality of subcells. One subcell functions as a broadband reflector, while each of the remaining subcells functions as a polarizing wavelength selective reflector. The number of the latter subcells depends on the number of wavelengths or wavelength bands to be separated. Each subcell in turn comprises a plurality of layers that are bonded together at their surfaces which are oriented at a 45.degree. angle relative to the horizontal surfaces of the PWS panel. In each subcell, the plurality of layers comprise two cholesteric liquid crystal, CLC, films which reflect at a selected wavelength, at least one phase shifting layer (optical retarder), and an appropriate number of clear substrates which provide mechanical supports. The thicknesses of the supporting substrates are designed to cause the optical beams transmitted through the PWS to be spatially separated by appropriate distances. Direct view displays and projection displays are simplified.

Claims17

Dependent claims

A polarizing wavelength separating optical element, for accepting from a source a linear periodic array of polychromatic optical beams and converting the beams with high conversion efficiency into beams that are circularly polarized, and separated spectrally and spatially in a selected order of wavelengths having a period identical to that of the source comprising

a periodic array of cells whose period is identical to the period of the light source, each cell in turn comprising a broadband reflecting layer arranged to reflect source light into and a plurality of subcells in number related to the number of wavelength bands to be separated, said array having an input surface and an output surface which are in parallel planes;
said subcells in turn each comprising a plurality of layers bonded together at an angle to said parallel surface planes of said array, said layers comprising:
(b) a plurality of selectively reflecting cholesteric liquid crystal layers
(c) at least one phase shifting retarder layer;
and
(d) a plurality of clear substrates of thickness selected to provide spatial separation between output optical beams.

3 more elements

Dependencies are inferred from the claim text.

Polarizing wavelength separator

Life of this patent

Polarizing wavelength separator

Life of this patent

Abstract

Claims17