Patent ID: 11968351
Assignee: NATIONAL TSING HUA UNIVERSITY
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H  G | IPC G  H

Claim 0:
1. A three-dimensional (3D) imaging method using scanning-type coherent diffraction, comprising steps of:
(A) by a light source that is moved relative to a sample object to N number of scanning positions one by one in a scanning manner, emitting, at each of the scanning positions, a coherent light beam toward the sample object while having a same orientation to form a light spot on the sample object, so as to define N number of light spot regions on the sample object that respectively correspond to the N number of the scanning positions, wherein N is a positive integer, and any adjacent two of the light spot regions partly overlap each other;
(B) by a two-dimensional (2D) photodetector, detecting, for the coherent light beam emitted by the light source at each of the scanning positions, diffraction of the coherent light beam that passes through the corresponding one of the light spot regions, so as to obtain N number of 2D diffraction data distributions that respectively correspond to the scanning positions;
(C) by a processor, using a mathematical coordinate transformation to map all data points of each of the 2D diffraction data distributions onto a 3D spherical coordinate system to generate a pair of spherical shells that are symmetric with respect to an origin of the 3D spherical coordinate system, and presenting all data points on one of the spherical shells in a 3D Cartesian coordinate system of a reciprocal space, so as to obtain N number of 3D intensity distributions in the reciprocal space, each of the 3D intensity distributions corresponding to one of the scanning positions to which the 2D diffraction data distribution corresponds, and being represented as Ij,qM, where j is an integer ranging from 1 to N;
(D) by the processor, performing, for each value of j from 1 to N, an iteration based on a sample function Oj,r that is related to a 3D structure of the sample object, a light source function Pj,r that is related to a structure of the light spot regions, and the 3D intensity distributions that respectively correspond to the scanning positions, so as to obtain a sample reconstruction function candidate and a light source reconstruction function candidate that correspond to the iteration, wherein the iteration includes operations of
(i) performing Fourier transform on a wave function ψj,r to obtain a distribution data φj,q for the reciprocal space, where the wave function ψj,r is defined as a product of the sample function Oj,r and the light source function Pj,r;
(ii) updating the distribution data φj,q in terms of amplitude based on one of the 3D intensity distributions Ij,qM that corresponds to the jth one of the scanning positions, so as to obtain an updated distribution data φ′j,q;
(iii) performing inverse Fourier transform on the updated distribution data φ′j,q to obtain an updated wave function ψ′j,r for a real space;
(iv) obtaining an updated sample function O′j,r and an updated light source function P′j,r based on the sample function Oj,r, the light source function Pj,r and the updated wave function ψ′j,r;
(v) when j≠N, repeating operations (i) to (iv) for a next value of j with the updated sample function O′j,r and the updated light source function P′j,r respectively serving as the sample function Oj,r and the light source function Pj,r for operation (i) in the repetition of operations (i) to (iv); and
(vi) when j=N, making the updated sample function O′j,r and the updated light source function P′j,r obtained in operation (iv) for j=N respectively serve as the sample reconstruction function candidate and the light source reconstruction function candidate for the iteration;

(E) by the processor, determining whether the sample reconstruction function candidate satisfies a predetermined convergence condition;
(F) by the processor, upon determining in step (E) that the sample reconstruction function candidate does not satisfy the predetermined convergence condition, repeating steps (D) and (E) with the sample reconstruction function candidate and the light source reconstruction function candidate respectively serving as the sample function Oj,r and the light source function Pj,r for operation (i) in the repetition of step (D) when j=1; and
(G) by the processor, after determining in step (E) that the sample reconstruction function candidate satisfies the predetermined convergence condition, making the sample reconstruction function candidate serve as a sample reconstruction function, executing a predetermined 3D graphics program to generate, based on the sample reconstruction function, a 3D envelope curved surface that corresponds to a specific value included in the sample reconstruction function, and that serves as a 3D reconstruction image of the sample object, and displaying the 3D reconstruction image on a display module.