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We propose a spectral matching imager using light-emitting diodes (LEDs) of narrowband spectral power distributions. Each spectral channel of the LED illumination undergoes amplitude modulation (AM) with one of an orthonormal set of carrier signals. This imager, which employs the correlation image sensor (CIS) as its imaging device, performs spectral correlation pixelwise between a reference spectrum and that of the object in every frame by demodulating the orthonormal AM carriers via temporal correlation. This sensing principle enables a higher efficiency in the use of illumination power than the spectral matching imager we originally proposed. A twelve-channel AM-coded multispectral light source is developed by assembling commercial LEDs. Under this LED light source, experiments were carried out on pairs of glass pieces of a similar color, but with different spectral transmittance functions. The results confirmed that the proposed imager successfully performed spectral matching on each pair of glass pieces in real time.

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