Wide angle spectroradiometer

Abstract

A spectroradiometer for the measurement of spectral irradiance (in μw cm-2 (3 nm)-1) in the wavelength range 420 nm to 1100 nm is described. It has an entrant system, consisting of an integrating sphere with a conical baffle inside, for obtaining good cosine response. A 250 mm Bausch and Lomb grating monochromator is used as a dispersing unit and narrow band energies are detected by an R.C.A. photomultiplier having S-1 type spectral response. The output is fed to a differential amplifier and the unbalanced anode current is calibrated for different wavelengths. The sensitivity at the wavelength of maximum response (740 nm) is 17.7 μw cm-2 (3 nm)-1 μA-1.