Study On The Three-Dimensional Dimension Measurement Of Fingerprint

Using grating fringe phase-shifting projection technology,the height distribution of human fingerprint was measured,and the 3D information of fingerprint was obtained.Nonlinear phase distortion is introduced in the imaging system used for fringe projection and image acquisition in fringe projection 3D topography measurement.In order to avoid this kind of nonlinear phase distortion introduced by the system error,we put forward through a series of step standard flat method,in the plane of the corresponding phase distribution of each position,through the phase distribution information from different parts of the tablet and the tablet mobile distance,the relation between the phase measuring system was set up-height transformation relations,The transformation of the three-dimensional phase distribution to the height distribution of human fingerprint is completed.The calibration technology can obtain different phase-height calibration coefficients in different regions of fingerprint,and avoid the systematic error introduced by the single phase-height transformation coefficient in traditional calibration methods.The research work is as follows:1.The three-dimensional scale measurement system of human fingerprint has been established.In grating stripe phase-shift projection system,fingerprint gathering place near a standard flat,by moving the vertical plane in a series of phase distribution of the position for each part of the plane,so as to establish corresponding relationship between phase-height,the phase-height conversion technology can avoid the projection system error caused by the nonlinear distortion stripes.2.Completed the corresponding computer program for the three-dimensional measurement of human fingerprint.The sinusoidal grating images required by the four-step phase shifting technology are produced by digital image technology.The phase of the fringe images is 0,??2,?,3??2,in order.The program can adjust the brightness and contrast of the grating to meet the experimental needs.In this paper,the phase unwrapping of the fringes obtained by the four-step phase shifting technique is carried out by using the flood filling algorithm,and the fingerprint 3D topography with phase as unit is obtained.3.The three dimensional height measurement of human fingerprint was carried out by using the three dimensional scale measurement system with phase-height calibration.The analysis of the measurement results of human fingerprint shows that this technique can achieve the height measurement of submillimeter scale,and can be used to measure a wide range of fine objects.