Abstract: An electro-optical system for rapid, accurate spectral analysis of the reflectivity or transmissivity of samples. A concave, holographic diffraction grating is oscillated at high speed to provide a rapid scanning of monochromatic light through a spectrum of wavelengths. The grating drive system is an electrically driven mechanical oscillator which utilizes the back EMF of the oscillator motor to maintain oscillation at the desired amplitude and frequency. A passive optical shutter mounted to the grating alternately blocks the light entering and exiting the monochrometer as the grating is oscillated. The resultant dark period is utilized by the system to provide a reference offset value and to control cooling of the detectors. A unique phase-locked loop circuit is employed to provide sample commands at precisely determined intervals to correctly correlate the spectral data with the output of the monochrometer. Source and exit optics are employed to optimally shape the light passing through the system.