Multiplexed spectrum approach for imaging spectroscopy

Most existing slit spectrometers disperse light into spatially separated spectral components and then record this spectral information on a photodetector (PD), normally in the form of an array. We propose an alternative system and method that allow for a small and reversible spatial overlap or multiplexing of image spectral components on individual pixels of a PD array. The spectral components are subsequently de-multiplexed by digitally processing 2-D data from the PD array. Our reversible spectral multiplexing method involves introduction of an intentional image pixel spread and of a small dispersive shift of the spectral components of each image pixel by a weak dispersive element (weakly diffracting diffraction grating or prism). Relations between image feature size, full spectral range and number of spectral bands are discussed. Results of computer simulations show that our method enables a regular digital imaging system based on an imager "chip" (e.g. CCD or CMOS type) and equipped with a light dispersing element to serve as an imaging spectrometer and to perform spectral imaging.