1. A diffuse reflectance spectroscopy system comprising: a source of energy; a sample at a sample plane; means to direct the energy from the source of energy to a focus at a field stop plane; a filter at the field stop plane operative to reflect the energy from the source of energy toward the sample in spatially separated energy bands; and means to direct the energy bands onto the sample at the sample plane in focus to form an image of the filter at the sample plane and to return energy reflected from the sample to the filter; the filter being operative to direct specularly reflected focused energy from the sample out of the system and to direct diffusely reflected unfocused energy from the sample to a detector.