Study On Three-Dimensional Contour Measurement Of Palm

In the high-speed information society,all works of life have high requirements for the speed and accuracy of identity recognition,such as finance,military,medical and travel.The rapid development of biometrics technology can meet the needs of rapid and accurate identification of a person's identity.Modern biometric recognition technology mainly includes face recognition,palmprint recognition,hand shape recognition,fingerprint recognition,iris recognition and voiceprint recognition.Among them,hand shape recognition technology has great development potential because of its unique recognition process.Palm contour recognition is one of the recognition methods in the hand shape recognition technology.Three-dimensional contour measurement technology plays an important role in industry,military,medical and other aspects.In this thesis,the non-contact three-dimensional contour measurement method will be used to reconstruct the three-dimensional contour of the palm.The non-contact three-dimensional contour measurement method avoids the direct contact between the palm and the measuring equipment,which can not only guarantee the personal safety,but also quickly and conveniently realize the reconstruction of the three-dimensional contour of the palm.In this thesis,we use laser interference,linear array laser and structured light projection to produce uniform fringes.Compared with general structured light projection,laser interference fringes have higher brightness and are less affected by ambient light.After using a high-resolution camera,you can measure the three-dimensional contour of large objects,such as the palm of a human hand,from a long distance.The linear laser array is a laser array composed of linear laser,which produces parallel stripe array.It not only reduces the requirements of the number of accessories on the optical path,simplifies the optical path,but also avoids the problem of stripe bending in laser shearing interference.The line laser array can also be used to measure the three-dimensional contour of the object with large area.In this thesis,the method of structured light projection mainly uses computer coding to generate fringe array.The width and density of fringe can be controlled artificially according to the experimental requirements,and it is easier to produce high-quality fringe array,so as to improve the experimental accuracy.In this thesis,the fringe array generated by theabove methods will be used to obtain the height information of the palm surface.After obtaining the stripes of the reference plane and the stripes modulated by the palm of the hand with the camera,we pre-process the image.This can reduce the influence of environment noise on the experiment.Fourier transform the image to the frequency domain,and then design the band-pass filter to filter the spectrum,which can effectively filter out the background components that are not needed in the experiment.At the same time,by controlling the bandwidth of the filter and other parameters,we can get the basic frequency components we need from the spectrum.The phase information of the hand's three-dimensional contour can be obtained by a series of calculation of the fundamental frequency component.In the process of using Fourier transform profilometry to get phase information,we will encounter the problem of phase truncation.The calculation results can not reflect the real three-dimensional contour information of the object.Which algorithm is used to unwrap the wrapped-phase is an important problem to be solved in this thesis.Finally,we compares the results of using several different methods to obtain the three-dimensional contour information of the palm.Then we get the advantages and disadvantages of each method,and improve the experimental scheme.