US Patent 7321377 Device and method for laser marking

When laser beams with a wavelength of 9.3 μm or 9.6 μm are used, a pulse width t (μsec) which is a radiation time of the laser beam and an energy density E (kw/cm2) of the laser beam on an X-ray film are set such that they meet requirements based on an area A between line segments A1 and A2. Moreover, when laser beams with a wavelength of a 10-micrometer band, such as 10.6 μm, is used, the pulse width and the energy density are set such that they meet requirements based on an area B between line segments B1 and B2. As a result, since the pulse width t is within a range of equal to or larger than 3 μsec and smaller than 30 μsec, a high-quality marking pattern with excellent visibility can be formed while improving the productivity of the X-ray film.