Instrument for measuring absolute reflectance and transmittance at cryogenic temperatures

Claim 1

AN OPTICAL SYSTEM ADAPTED FOR USE IN MEASURING ABSOLUTE REFLECTANCE AND TRANSMITTANCE OF ELECTROPOLISHED SINGLE CRYSTAL SAMPLES COMPRISING IN COMBINATION: A HORIZONTALLY ROTATABLE LIQUID HELIUM DEWAR INCLUDING MEANS DEFINING THEREIN A SEALED AND EVACUATED CHAMBER HAVING AT LEAST ONE PAIR OF OPPOSED CAVITIES COMPRISING TRANSPARENT PLANE-SURFACED WINDOWS ADAPTED TO TRANSMIT AN EXTERNALLY GENERATED BEAM OF LIGHT TRANSVERSELY THROUGH SAID CHAMBER; CRYSTAL SUPPORT MEANS ARRANGED WITHIN SAID CHAMBER FOR SUPPORTING A SINGLE CRYSTAL SAMPLE HAVING A POLISHED SURFACE IN A BEAM INTERRUPTING POSITION WITHIN SAID CHAMBER AND BETWEEN SAID WINDOWS SO THAT SAID POLISHED SURFACE IS IN A SUBSTANTIALLY PARALLEL RELATIONSHIP WITH RESPECT TO THE PLANE SURFACES OF SAID WINDOWS AND EXTENDS ALONG THE VERTICAL AXIS OF ROTATION OF SAID DEWAR; A SOURCE OF LIGHT; A DOUBLE-MONOCHROMATOR OPTIC SYSTEM, INCLUDING AN EXIT PUPIL, FOR PRODUCING FROM SAID SOURCE A MONOCHROMATIC BEAM OF LIGHT;