A generalized amplitude-phase retrieval algorithm (GAPRA) attack on ‘double images encryption method with resistance against the special attack based on an asymmetric algorithm’ (DIEM) is presented in this paper. The analysis shows that the DIEM is a cascaded cryptosystem, which consist of a joint transform correlator architecture and a phasetruncated Fourier transform scheme. A GAPRA attack is proposed and the potential risk of the cascaded cryptosystems is discussed. By using our method, an attacker could crack high-quality results of the plaintexts. A set of simulation results demonstrate the validity and feasibility of the proposed method.
In this paper, we proposed a novel method for correcting the 2D calibration target. Firstly, we captured
multiple images of the inaccurate calibration target from multi-views and located the coordinates of
those circle landmarks in these images. Secondly, homonymous landmarks in different images could be
detected by a scheme for a special topology relation. Thirdly, we could accurately reconstruct the 3D
coordinates of landmarks with a scale constraint using bundle adjustment strategy. And finally, the
scale was computed from an accurate distance between any two landmarks. Then we could obtain the
truly coordinates of landmarks, which multiplied by the scale. The experimental results validated that
our method is efficient, high-precision, low-cost and easy-implementation, which can be widely
applied in vision measurement and system calibration.
A phase reconstruction method using frequency-shifting is proposed. The frequency-shifting method is
developed based on the properties of trigonometric functions. The computer simulation and the
experimental result are also presented to demonstrate the feasibility and validity of the proposed
approach in phase reconstruction.
Circular targets are commonly used in vision measurement and photogrammetry. Due to the asymmetric projection, the geometric centroid of the ellipse projection and the true projection of the target center are not identical, which leads to a systematic center location error. A method to correct the center location error is presented in this paper. Surface normal directions of circular targets are determined by camera calibration in advance. Then the correction values of the geometric centroids are calculated with space analytic geometry. The experimental results show the improvement of accuracy can be achieved after error correction by our method.