A Rapid-Scan Spectrometer That Sweeps Corner Mirrors Through the Spectrum

Abstract

By sweeping a sequence of corner mirrors through an intermediate focal plane, a grating spectrometer can be converted to rapid scanning without loss of optical quality. We have developed an instrument using this principle to scan the first order spectrum of a diffraction grating in 1 msec, at rates up to 800 scans/sec. In our design, twenty-four corner mirrors are mounted on the periphery of a dynamically balanced rotating scan wheel, tangential to the intermediate focal plane of a double-pass CzernyTurner monochromator. Specific features include readout linear in time and wavelength, foreoptics focusable from 28 cm to infinity, absolute radiance calibration, and interchangeable gratings and detectors for the region 2500 A to 9 micro. Performance is limited only by the detector signal-to-noise ratio determined by the scan time and the electrical bandwidth required, and is not limited by the optical scanning technique. Spectra illustrating instrument performance are presented.