Optical method for personal identification based on recognition of three-dimensional objects

We propose an optical method of personal identification utilizing three-dimensional information about a portable object, for which we choose a seal in the present study. The three-dimensional information about the seal, i.e., its engraved design and engraved depth, is recorded with a charge-coupled device (CCD) camera as a two-dimensional oblique projection. For identification, a target projection is compared with a reference projection on the basis of the joint transform correlation (JTC). In order to enhance the detail of the projections for better discrimination, we adopt the modified JTC in which, instead of employing the power spectra of the target and reference projections, their logarithms are used. The feasibility of the proposed method is examined by computer simulation as well as by optical experimentation, and satisfactory results are obtained.