Abstract: Aimed at measuring the bullet mark on the helmet, the fringe projection Fourier Transformation Profilometry (FTP) based on double reference surfaces is proposed. The second reference surface, which is the helmet surface without damage, is introduced. This method is different from the convenient measuring method, which only uses one reference plane, and avoids the loss of information and insures accuracy in measurement. Experiments prove that this method is availd, and that precision is up to 0.1mm.

Key words: Fourier transformation profilometry, 3-D profile measurement, double reference surface, bullet mark