Resolving power of a quantum photometer

An analysis is made of the spectral and spatial resolving powers of a quantum photometer, which is an instrument for absolute (free of reference standards) measurement of the spectral density of the energy brightness of electromagnetic radiation on the basis of three-frequency parametric conversion. General expressions are obtained for the frequency and angular intervals, and also for elements of the area of the beam cross section over which averaging is carried out in the determination of the spectral density of the brightness. The dependence is determined of the resolving power of a quantum photometer on the characteristics of a parametric converter and of a recording system used in this photometer.