AM-coded spectral matching imager using multispectral LED illumination

This paper proposes a spectral matching imager using light-emitting diodes (LED´s) that have different narrow-band spectral distributions and also are amplitude-modulated with orthogonal carriers. This imager, which consists of the correlation image sensor, performs pixelwise spectral matching between a reference spectrum and that of the object in each frame, based on spectral-channel-wise temporal correlation between the orthogonal amplitude modulation (AM) carriers. Using a twelve-channel AM-coded multispectral LED light source, this imager successfully discriminated glass pieces of similar color but with different spectral transmittance functions.