In a three-dimensional image scanner, a grating projection type moire topography is used, so as to capture three-dimensional form information of an object to be measured easily in a short time with a high degree of freedom in measurement. The front-face body is formed from a front-face body main body made of a crystalline metal, and a face plate which is fitted in an opening of the front-face body main body and fixedly attached thereto by means of caulking and which is made of an amorphous metal. A first summer module generates a first accumulated difference based on a sum of values of the first difference generated during a predetermined period. The interface unit includes storage and other logic elements that compensate for the differences in clock speeds and in rates of data exchange between the emulation unit and the target processor.