Image multispectral sensing

Abstract

A spectrophotometer useful for spectral analysis of light emanating from one or more targets within an image is described. The apparatus comprises a diffractive lens having an optical axis, a planar array of photodetector elements (pixels), a means for changing the distance between the photodetector array and the diffractive lens along the optical axis and a signal processor. If either the photodetector array or the lens is moved along the optical axis, different wavelengths of light from each target within the image come into and out of focus on particular photodetector elements in the plane of the photodetector array generating sequential images corresponding to different wavelengths. By tracking each pixel's output in the photodetector array as a function of lens position relative to the photodetector array, the spectral composition of each target within the image is generated. Background (non-target) radiation will generally appear as a broad spectrum while light emanating from targets will have a fine spectral signature which is easily differentiated from the background. The sequential images from the photodetector array are processed so that only discrete spectral components are retained for each photodetector array position. Each target's spectrum is built up from sequential images and may be compared with a library of known target signatures for purposes of recognition.

Dependencies are inferred from the claim text.