A diffraction grating and a prism with the appropriate characteristics are employed to provide a combined dispersive characteristic that is substantially linear over the visible spectrum. Radiation from the grating and prism is collimated by a lens towards a detector array. The grating or a telecentric...http://www.google.com/patents/US7408638?utm_source=gb-gplus-sharePatent US7408638 - Refractive-diffractive spectrometer
