A reflectometer has been constructed for the purpose of measuring the diffuse reflectance of living tissue and inert materials for visible and infrared radiation. Appreciable energy from the sources generally employed in studies of the effects of intense thermal radiation on materials falls in the infrared region between 1.0 and 2.8 microns. While commercial instruments are available for measuring the spectral reflectance of diffusing materials in the ultraviolet, visible, and near infrared regions up to 1.0 micron, instrumentation for obtaining corresponding data further into the infrared is inadequate.
The reflectometer consists of a 6-inch diameter aluminized-glass hemispherical collecting mirror and a flat lead sulfide photocell receiver. A Perkin-Elmer Model 83 Universal monochromator is employed as the dispersing unit. A beam-splitting chopper, placed between the monochromator and reflectometer, permits the use of a reference or monitor receiver to control the slit opening and thus the radiant energy to the reflectometer. The wavelength range for automatic scanning is from 0.5 to 2.7 microns. The recorder traces are not direct-reading, but must be corrected for differences in the spectral response of the signal and reference photoconductive cells and the reflectance of the reference standard and that of the hemisphere.
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