1. A signal processing system comprising: a base vector acquisition unit configured to acquire a dedicated base vector based on a known spectral characteristic of a subject as an identification target; a system spectral characteristic acquisition unit configured to acquire a spectral characteristic of an imaging system including a spectral characteristic concerning a color imaging system used for image acquisition of subjects including the subject as the identification target and a spectral characteristic concerning illumination light used when image acquisition of the subjects by the color imaging system; a calculation unit configured to calculate a weighting factor concerning the dedicated base vector based on an image signal obtained by image acquisition of the subject by the color imaging system, the dedicated base vector, and the spectral characteristic of the imaging system; and an output signal calculation unit configured to calculate an output signal as an identification result of the subject which is the identification target based on the weighting factor concerning the dedicated base vector calculated by the calculation unit.