Processing And Analysis Of Regular Interference Fringe Pattern

Analysis of interference fringe is a critical step in modern interference technique.By analyzing the interference fringe we can obtain the effective information such as the fringe radius,the fringe spacing,the fringe period and the fringe contrast.These information can be used to finish the measurement of wave front,surface roughness,optical mirror,strain and displacement and velocity.In this paper,the image processing method is used to measure and analyze the radius of Newton ring interference fringes and the spacing of straight interference fringes.A method for measuring fringe radius of Newton's rings is presented in this paper,which is based on the regional gravity method,polar coordinate transform and gray projection in horizontal direction.Firstly,the public center of Newton's rings interference fringes are obtained by using the regional gravity method,and then ring fringes can be expanded around the public center by using the polar coordinate transform.Finally,in the horizontal direction,the transformed result is projected and further radius of Newton's rings interference fringes can be obtained.The method can obtain the radius of ring fringes that need not to be got from the fringe contour directly.The simulated results indicate that the measuring accuracy under the effect of random noise can keep the degree of less than 0.5 pixels.Meanwhile,for the interference straight fringes,a method is presented for measuring it spacing,which based on Fourier transform,polar coordinate transform and gray projection in a direction.Firstly,the oblique direction of the straight fringes is obtained by using the power spectrum and the result from polar coordinate transform.Then the straight fringes are projected according to the oblique angle.Finally,the spacing of the straight interference fringes is obtained according to the result of projection.The simulated results indicate that the measuring accuracy under the effect of random noise can keep the degree of less than 1 pixels.Besides,in order to verify the validity and reliability of the proposed method,Newton's rings interference fringes pattern and the straight interference fringes pattern are obtained by the experimental device.Furthermore,the radius of Newton's rings interference fringes and the spacing of the straight interference fringes are measured by using the proposed method respectively.The experimental results show that the proposed methods have good feasibility and reliability.