Measurement Of Continuous Deformation Based On Digital Holography

With the rapid development of computer technology and the endless refinement of the performance of photoelectric sensors,the research and the application of digital holographic technology has drawn more and more attentions.We could realize 3-D image recognition,measurement of contour of object and micro-deformation detection with the aid of digital holographic interference technique.However,with the new developments and requirements in industrial technology,it is an urgent need to measure the large deformation and the continuous deformation automatically.It could be well achieved with digital holographic technology which integrated the optical holographic interference technique and the superiority of fast processing ability of computer.This paper reviewed the basic principle of optical holography and digital holography,the theory of Fresnel diffraction and Fourier transform.The methods for removing the zero-order light and the conjugate image of reconstruction light of digital hologram were introduced.The difference digital hologram method to deal with the measurement of object deformation based on double-exposure digital holographic interference technique was proposed,which is a new way,and its feasibility and superiority has been proved theoretically and experimentally.In addition,the methods for measurement of large continuous deformation by digital holography were also proposed.The research process mainly include:(1)designing and setting up the experiment system;(2)recording the digital holograms of the typical intermediate states in the process of object continuous deformation;(3)getting,extracting and processing the interference fringes which reflect the relative deformation between two adjacent intermediate states based on difference digital hologram method;(4)interpreting,analyzing,calculating and displaying the interference fringes by MATLAB soft wear and then obtaining deformation values of the representative points on the object;(5)drawing the 3-D figures of deformation with the numerical fitting method;(6)realizing the measurement of large deformation through overlying the many intermediate small deformations;(7)analyzing the deviation of result and proposing corresponding solutions.The proposed method overcomes the limit of double-exposure holographic interference and shows the convenience and flexibility of the digital holographic technology on holographic recording and digital process for continuous deformation measurement.In addition,we can realize the real-time measurements.It makes a breakthrough in technology and shows a promising application potential.