Three-phase quadrature spectral matching imager using correlation image sensor and wavelength-swept monochromatic illumination

摘要

We propose a three-phase spectral matching imager (3PSMI) to realize a novel spectral matching method called quadrature spectral matching (QSM) in real time. The 3PSMI is comprised of the correla-tion image sensor (CIS) and wavelength-swept monochromatic illumina-tion (WSMI) to perform QSM at each pixel on the CIS at a video frame rate. QSM consists of spectral correlation between an ac component of an object spectrum and an orthonormal pair of reference spectra, being equivalent to projecting the ac object spectrum onto a two-dimensional subspace spanned by the reference spectra. Similarity of the ac object spectrum to the reference spectra is evaluated in terms of the azimuth an-gle of the projection, independently of the norm of the ac object spectrum as well as spatial intensity distribution of the WSMI. A programable spec-tral light source is employed to implement the WSMI so that the spectral characteristics of the WSMI and CIS cancel each other and thus do not af-fect QSM on the 3PSMI. Experimental results confirm that the developed 3PSMI system can distinguish objects with smaller difference in spec-tral reflectance in real time than RGB imaging with off-the-shelf cameras.