GRADATION LASER MARKING METHOD AND TRANSPARENT BODY HAVING MULTILEVEL IMAGE

PROBLEM TO BE SOLVED: To provide stereoscopic expression, i.e., expression of depth, by marking with gradation and shades like a photographic image, in a thin target material having transparency for a laser beam, and by making stereoscopic expression based on two-dimensional data. SOLUTION: With the diameters D1, D2, Dn and the longitudinal lengths L1, L2, Ln, of a minute crack in an object 1 for gradation marking, a growing process of the minute crack is indicated by D1, D2, Dn for the diameter in the lateral direction and by L1, L2, Ln for the length in the longitudinal direction, respectively in accordance with the LPn conditions of a pulsed laser beam, i.e., pulse time, laser energy and pulse irradiation frequency. These appearances of the minute crack are formed by variably controlling the output, the emission duration, and the energy of the laser beam, therefore, the degree of the marking can be expressed as gradation through the difference of the appearances of the minute crack. COPYRIGHT: (C)2006,JPO&NCIPI