The present invention relates to a method and apparatus for clearly imaging samples such as fingerprints on substrates of forensic samples. The present invention overcomes the problems of the Laser-Induced-Fluorescence (LIF) technique to distinguish fluorescence from the sample from that of the substrate. The method of the present invention uses either a homodyne- or a heterodyne-assisted phase resolving method, or both, to suppress the contribution of the substrate fluorescence. The resulting image of the sample will then be sufficiently clear for forensic purposes. The present invention may also be used on histological and biochemical samples to visualise latent images.