Provided is a reliable or accurate optical detection method or such an optical imaging method. Also provided is an application technique using such a method. At least a part of an optical path starting from a light-emitting source or reaching a photodetector includes a plurality of optical paths. At a predetermined position of the optical path, beams of light after passing through the plurality ofoptical paths are mixed. This mixed light is used for optical detection or optical imaging. An optical-length difference among beams of light passing through the plurality of optical paths may be longer than the coherence length. Means for feed-backing predetermined characteristics of a target to the optical characteristics to be used for optical detection or optical imaging may be included. Suchmeans may be used separately from the above. Such means may be applied to another technique, an application material or an application program.
Light-source unit, measurement apparatus, near-infrared microscopic apparatus, optical detection method, functional bio-related substance, and state management method