The Air Force Weapons Laboratory laser window test apparatus

The Laser Window Test Apparatus (LWTA) evaluates windows and other optical components for high-power infrared laser systems. Specimens are probed with narrow beams from low-power lasers (currently CO2 lasers) to determine their optical characteristics at incidence angles between 2 and 76 degrees from the normal. The instrument includes a photometer that uses digitized ratiometric detection for measuring single-pass transmittance and single-pass reflectance; an interferometer for measuring the optical pathlength through specimens; a rastering machine for moving the specimens in relation to the probing beams; and a minicomputer controls measurements, performs on-line calibrations, computes running statistical records of the acquired data, and generates an output tape of all data for use by a CDC-6600 computer program which generates the data in its final form and accuracy. (Modified author abstract)