Abstract: In one aspect of the invention, the sample surface is wetted with an aqueous solution of a fluorescent dye followed by rinses with water to remove an excessive amount of the dye so that the background fluorescence emission can be minimized to increase the efficiency of fingerprint detection. In another aspect, the fluorescent dye or a reagent to produce fluorescent substance is deposited on the sample surface by attaching a gelatinous film impregnated with a solution thereof followed by peeling. In a further different aspect, a powdery fluorescent dye is deposited on to the sample surface followed by spraying of water to wash away an excessive amount of the powdery dye so that the background fluorescence can be minimized. The invention also provides an apparatus for the fingerprint detection by the laser beam excitation of fluorescence, which is compact and portable as being composed of an ingenious combination of several units into an integral system.

Abstract: In one aspect of the invention, the sample surface is wetted with an aqueous solution of a fluorescent dye followed by rinses with water to remove an excessive amount of the dye so that the background fluorescence emission can be minimized to increase the efficiency of fingerprint detection. In another aspect, the fluorescent dye or a reagent to produce fluorescent substance is deposited on the sample surface by attaching a gelatin film impregnated with a solution thereof followed by peeling. In a further different aspect, a powdery fluorescent dye is deposited on to the sample surface followed by spraying of water after removing an excessive amount of the powdery dye so that the background fluorescence can be minimized. The invention also provides an apparatus for the fingerprint detection by the laser beam excitation of fluorescence, which is compact and portable as being composed of an ingenious combination of several units into an integral system.