In order to improve the security of traditional encryption systems, hyper-chaotic systems are introduced into the field of quantum image encryption. Firstly, the image is bitwise XOR by He fractional order hyper-chaotic Rabinovich system, and then the color image is represented as a quantum superposition state. The quantum image is scrambled by the unitary matrix generated by Logistic hyper-chaotic sequence, and then a hyper-chaotic sequence is generated to randomly replace the red, green and blue primary colors of each pixel to achieve the purpose of quantum image encryption. Finally, numerical simulation experiments are carried out on a computer. The experimental results show that the histogram of the encrypted image is flatter and even, the pixels are evenly distributed between 0 and 255, the correlation between adjacent pixels of the image is low. The average correlation coefficients of the red, green, and blue pixels of the encrypted image are 0.0012, 0.0025, and 0.0018. The system has high key sensitivity and can effectively resist statistical analysis attacks. The algorithm has good security and robustness.
The distorted checkerboard image affects the precision calibration in omnidirectional camera calibration due to inaccurate localization of features points. To solve this problem, an iterative refinement method is presented. Firstly, the initial-parameters are obtained from the traditional calibration method and the distorted checkerboard images are corrected to world coordinate system. Then, the features points are located in those undistorted images. The calibration parameters are recomputed in an iterative refinement until convergence. This iterative refinement method improves localization accuracy of feature points and consequently of camera calibration. The correctness and effectiveness of the method is proved by simulation experiments and physical experiments. The experiments show that the rep rojection error is reduced by 38% compared to traditional methods.
Illumination design used to redistribute the spatial energy distribution of light source is a key technique in lighting applications. However, there is still no effective illumination design method for the removing of the chromatic dispersion. What we present here is an achromatic lens design to enhance the efficiency and uniform illumination of white light-emitting diode (LED) with diffractive optical element (DOE). We employ the chromatic aberration value (deg) to measure the degree of chromatic dispersion in illumination systems. Monte Carlo ray tracing simulation results indicate that the chromatic dispersion of the modified achromatic collimator significantly decreases from 0.5 to 0.1 with LED chip size of 1.0mm×1.0mm and simulation efficiency of 90.73%, compared with the traditional collimator. Moreover, with different corrected wavelengths we compared different chromatic aberration values that followed with the changing pupil percent. The achromatic collimator provided an effective way to achieve white LED with low chromatic dispersion at high efficiency and uniform illumination.