Design of glass filter combinations for photometers.

Two nonlinear curve-fitting computer programs have been developed for designing subtractive glass filter combinations for use in hotoelectric photometers. One program adjusts the filter thicknesses to minimize the sum of squares of errors at each wavelength and is thus useful in designing a general purpose instrument. The second program minimizes the errors in the photometric measurements of preselected light sources. Filters for correcting various photoelectric detectors to the CIE luminous efficiency function are specified. Several spectral response functions have been utilized including S-4, S-10, S-11, S-20 types, and those of typical silicon diodes, and selenium cells. Practical photometer designs with predicted measurement errors of less than 0.1% are presented.