1. A signal processing system comprising: a base vector acquisition unit configured to perform an acquisition of a base vector based on spectral characteristics of a subject to be an identification object with spectral characteristics known; a separation unit configured to separate an image signal, which is composed of a plurality of color signals obtained by a color imaging system provided for subjects including the subject to be the identification object, into image signals of a plurality of wavelength areas based on the plurality of color signals; a system spectral characteristics acquisition unit configured to perform an acquisition of spectral characteristics of an image acquisition system including spectral characteristics concerning the color imaging system and spectral characteristics concerning illumination light used in image acquisition of subjects by the color imaging system; a calculation unit configured to calculate a weighting coefficient concerning the base vector for the each wavelength area, based on the image signals of the plurality of wavelength areas separated by the separation unit, the base vector acquired by the base vector acquisition unit, and the spectral characteristics of the image acquisition system acquired by the system spectral characteristics acquisition unit; and an output signal calculation unit configured to calculate an output signal as identification result of subject to be identification objects with the spectral characteristics known, based on the weighting coefficient concerning base vector for the each wavelength area calculated in the calculation unit.