SMOOTHING OF IRRADIANCE SPECTRA WITH FINITE-BANDWIDTH WINDOWS, WITH APPLICATION TO PARTICLE-SIZE ANALYSIS

The problem is investigated of obtaining minimum-bias spectral estimates under the constraint of finite spectral-window bandwidth. The problem is meaningful for spectral estimation with a coherent optical system in which the power-spectrum estimate, i. e. , the Fourier irradiance, is physically available for smoothing. An example that deals with the smoothing of statistically unstable optical data is furnished in connection with the problem of particle-size estimation with an optical-digital computer. It is shown that the smoothing of the irradiance spectrum prior to particle-size estimation furnishes more satisfactory results than operating with unsmoothed data.