Low-distortion imaging spectrometer designs utilizing convex gratings

Several designs are described that are based on the Offner concentric spectrometer form, with the grating formed on the convex secondary mirror. It is shown that these designs permit the reduction of spectral and spatial distortion to a small (similar to 1%) fi action of a pixel, while also providing a compact form with excellent optical correction. These designs can satisfy the needs and tight calibration requirements of imaging spectrometers for Earth remote sensing, over a broad spectral range from the ultraviolet to the thermal infrared. The practical realization of the designs owes much to the recent development of convex grating fabrication by electron-beam lithography.