An imaging spectrometer, covering the visible through infrared wavelengths, which disperses the light by a plane diffraction grating behind a wedged optical element. This design uses an achromatic doublet lens with a reflective coating on its convex back surface to produce the spectra on a flat detector. Spatial keystone distortion and spectral smile are controlled to less than one tenth of a pixel over the full wavelength range, facilitating the use of simple retrieval algorithms.