Abstract
A wavelength-modulated spectrometer usable for reflectivity measurements between 150 nm and 900 nm is described. The chopped double-beam, single-detector system measures conventional and derivative spectra simultaneously. The cancellation of spurious derivative signals due to the modulated incident light is performed by an electronic servo-loop using multiplier modules. The direct and modulated reflectance spectra of cubic ZnS between 165 nm and 360 nm are given.