Three-dimensional Profile Measurement Of Fingerprints

The three-dimensional profile of the fingerprint of the human body was measured by the grating projection fringe three-dimensional profile measurement system.The traditional two-dimensional fingerprint recognition uses the optical total reflection contact acquisition method,which only obtains the distribution information of the texture direction,simultaneously the contact type acquisition may cause the fingerprint image deformation because of the finger pressure uneven,thus brings the measurement error,reduces the recognition system accuracy.The contactless 3D fingerprint technology not only obtains the texture distribution of the fingerprint in the traditional technology,but also can obtain the relative height fluctuation information of the fingerprint,which greatly increases the amount of fingerprint information acquisition,thus improving the fingerprint identification efficiency and the security of the system.In this paper,a three-dimensional measurement experiment system is established for finger fingerprints with high accuracy and complex surface morphology.The sinusoidal optical fringes are projected onto the fingers,and the deformed fringe images on the fingerprints are obtained by digital photography.By using the flood fill algorithm to perform the phase unwrapping operation on the obtained parcel phase,and finally calculates the three-dimensional topography of the fingerprint.The main research contents are as follows:1.Using computer image processing technology to produce a sinusoidal projection fringe image.The phase of the raster fringe image is 0,?/2,?,3?/2,and the raster fringe contrast is0.8.2.A three-dimensional face measurement system for human fingerprints was established.The sinusoidal raster image is projected on the surface of the finger through a high-definition projector in order of phase,and a CCD camera is used to capture a raster image that is deformed by the highly modulated fingerprint.3.Write a raster image processing program that is deformed by the fingerprint height modulation,and obtain the fingerprint height distribution related to the deformation amount.The wrapping phase of each pixel is obtained based on four grating fringe images with different phases.Using flood filling method,a pixel with a known phase value is selected,and this point is used as the starting point of the calculation.The wrapping phase expansionoperation is sequentially performed from all four sides to obtain the fingerprint morphology information.4.Through the measurement of human finger fingerprints by a three-dimensional surface measurement system,a relatively complete three-dimensional fingerprint morphology is obtained.By analyzing and comparing the experimental results,you can see clear fingerprint lines and node characteristics.This research method can also be applied to the measurement of the three-dimensional profile of other objects with subtle and complex shapes like human fingerprints.