Stationary, electrically alterable, optical masking device and

Abstract

An improved masking device for optical-type radiations is provided and employed in improved optical apparatus, such as spectrometers, requiring alterable radiation masking. The masking device involves no movable parts, is adapted to operate in a fixed position and has radiation transmission and/or reflection characteristics which are selectively alterable merely by controlling electrical excitation applied to the device. The masking device typically has a plurality of separated and predisposedly offset, coplanar zones of solidified, electro-optically active material carried upon a typically transparent substrate and bounded by areas of an opaque material. The active material may be any of the crystalline or polycrystalline materials which have the property of changing their optical characteristic between being relatively transmissive and being relatively reflective and/or opaque for radiations of the wavelengths of interest, in response to the passage of electrical current through the material. Alteration of the optical masking pattern configuration of the masking device under electrical control is sufficiently rapid to accommodate to computerized optical apparatus, such as infrared spectroscopic systems utilizing Hadamard transforms or analogous mathematical techniques.