AM-coded spectral matching imager using correlation image sensor

In the previous report we proposed the spectral matching imager, which, using the correlation image sensor, detects an object having a particular spectral function out of a scene under a typical frame rate. In order to increase power efficiency of the illumination, this paper proposes a type of spectral matching imager that uses AM-coded multispectral illumination instead of the variable wavelength monochrome illumination used previously. The AM-coded multispectral illumination projects a white light each wavelength of which is amplitude-modulated with a different frequency. Using a reference signal created as a weighted average of the AM waveforms of the illumination in which the weights are the values of a reference spectral function sampled at corresponding wavelengths, the imager outputs pixelwise spectral correlation between the object and the reference, due to orthogonality of the sinusoidal AM waveforms. The theory and an implementation of the imager are described.