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

Claim 5:
6. A three-dimensional (3D) imaging system using scanning-type coherent diffraction to reconstruct a 3D image for a sample object, said 3D imaging system comprising:
a light source movable on a movement plane that faces a surface of the sample object in a spacing direction, and operable to emit a coherent light beam toward the surface of the sample object while having a specific orientation;
a light source driver module configured to drive movement of said light source to N number of scanning positions on the movement plane one by one in a scanning manner, so that said light source, at each of the scanning positions, emits the coherent light beam toward the sample object while having the specific orientation to form a light spot on the sample object, thereby defining 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;
a two-dimensional (2D) photodetector disposed to detect, for the coherent light beam emitted by said 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, wherein the movement plane, the sample object and said 2D photodetector are arranged along the spacing direction;
a processor electrically connected to said 2D photodetector for receiving the 2D diffraction data distributions, and including:
a coordinate transformation module that is configured to use 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 configured to present 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 from 1 to N;
an iteration module configured to perform, 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 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 of the iteration;

a convergence determination module configured
to determine whether the sample reconstruction function candidate satisfies a predetermined convergence condition,
to, upon determining that the sample reconstruction function candidate does not satisfy the predetermined convergence condition, cause said iteration module to repeat the iteration 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 the iteration, and
to, after determining that the sample reconstruction function candidate satisfies the predetermined convergence condition, make the sample reconstruction function candidate serve as a sample reconstruction function that is a phase-retrieval sample function; and

a reconstruction module configured to execute 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

a display module electrically connected to said processor, and operable by said processor to display the 3D reconstruction image.