Patent ID: 7002697

Claim:
An optical instrument comprising: a thermo-optically tunable, thin film, free-space interference filter having a tunable passband which functions as a wavelength selector, said filter comprising a sequence of alternating layers of amorphous silicon and a dielectric material deposited one on top of the other, said sequence of alternating layers forming a Fabry-Perot cavity structure including: a first multi-layer thin film interference structure forming a first mirror; a thin-film spacer layer deposited on a top surface of the first multi-layer thin-film interference structure, said thin-film spacer layer made of amorphous silicon; and a second multi-layer thin film interference structure deposited on a top surface of the thin-film spacer layer and forming a second mirror; a lens for coupling an optical beam into the filter; an optical detector for receiving the optical beam after the optical beam has interacted with the interference filter; and circuitry for heating the thermo-optically tunable interference filter to control a location of the passband.