Spectral imaging apparatus and methods are disclosed. In one embodiment, a spectral imaging apparatus includes a spectral imaging apparatus includes a diffraction grating having one or more entrance apertures formed therein, a collecting reflecting element for reflecting said incident radiation to a diffractive surface of said diffraction grating, and a reimaging system adapted to provide a spectral image at a focal surface. The collecting reflecting element may include an aspherically-shaped portion, and the entrance apertures may be distributed along a straight or a non-straight axis. Alternately, optical fibers may be disposed in the entrance apertures. The spectral image provides a spectrum of radiation such that a first portion of the spectrum of radiation from a first region can be distinguished from a second portion of the spectrum of radiation from a second region.