Improvement of Fresnel Diffraction Convolution Algorithm

Abstract

With the development of digital holography, the accuracy requirements for the reconstruction phase are becoming increasingly high. The transfer function of the double fast transform (D-FFT) algorithm is distorted when the diffraction distance is larger than the criterion distance dt, which reduces the accuracy of solving the phase. In this paper, the Fresnel diffraction integration algorithm is improved by using the low-pass Tukey window to obtain more accurate reconstructed phases. The improved algorithm is called the D-FFT (Tukey) algorithm. The D-FFT (Tukey) algorithm adjusts the degree of edge smoothing of the Tukey window, using the peak signal-to-noise ratio (PSNR) and the structural similarity (SSIM) to remove the ringing effect and obtain a more accurate reconstructed phase. In a simulation of USAF1951, the longitudinal resolution of the reconstructed phase obtained by D-FFT (Tukey) reached 1.5 μm, which was lower than the 3 μm obtained by the T-FFT algorithm. The results of Fresnel holography experiments on lung cancer cell slices also demonstrated that the phase quality obtained by the D-FFT (Tukey) algorithm was superior to that of the T-FFT algorithm. D-FFT (Tukey) algorithm has potential applications in phase correction, structured illumination digital holographic microscopy, and microscopic digital holography.

A New Method for Detecting Weld Stability Based on Color Digital Holography

“…When y changes from 630 pixels to 720 pixels (red box), the slopes of all three curves show significant changes, which are caused by changes in the thickness and material of the weld, leading to changes in the elastic modulus. On the other hand, by calculating the holographic reconstruction images of the aluminum alloy plate [27,32], it can be seen that the thickness around the weld increases significantly (red box), and the position of the weld coincides with the range of significant changes in the slope of the three curves. Therefore, the position of the weld can be accurately determined by the center profile of the upward displacement field in the y-direction.…”