We propose an effective optimization method for generating smooth freeform surfaces for light-emitting diode(LED)non-rotational illumination based on ray targeting.This method begins with a starting design and goes through two optimization steps.An initial estimate is determined using a partial differential equation(PDE)method and a variable separation mapping.In the first optimization step the merit function is developed with ray targeting to ensure the shape of the illumination pattern.The purpose of the second optimization is to further improve the optical performance by constructing the merit function with uniformity and efficiency.Smooth freeform reflective and refractive surfaces,which can produce a uniform rectangular illumination without rotational symmetry,are designed using this method.The results show that uniform rectangular illumination is achieved and that smooth freeform surfaces are obtained.With ray targeting,the design efficiency can be significantly enhanced,and excellent optical performance can be achieved.
Reng-mao WUPeng LIUYa-qin ZHANGZhen-rong ZHENGHai-feng LIXu LIU
The number of layers and the resolution of liquid crystal displays （LCDs） limit the reconstruction fidelity of near- eye light field displays based on multilayer LCDs. Because the eye＇s resolution capability is different for central vision and peripheral vision, the fidelity can be improved by setting different weights for different areas. First we employ the eye＇s modulation transfer function （MTF） to acquire the limiting resolution angle. Then, due to the inverse relationship between the limiting angle and the weight values, the weighted function related to retinal eccentricity is calculated. In combination with the linear least-squares algorithm, the peak signal-to-noise ratio （PSNR） of the reconstructed scene is raised. The simulation results indicate that the weighted optimization algorithm can improve the image fidelity and reconstruction accuracy.
Based on light field reconstruction and motion recognition technique, a penetrable interactive floating 3D display system is proposed. The system consists of a high-frame-rate projector, a flat directional diffusing screen, a high-speed data transmission module, and a Kinect somatosensory device. The floating occlusioncorrect 3D image could rotate around some axis at different speeds according to user＇s hand motion. Eight motion directions and speed are detected accurately, and the prototype system operates efficiently with a recognition accuracy of 90% on average.
A light field three-dimensional （3D） display with multi-projectors and a concave screen is proposed. The system sets the viewing area at the center of the concave screen, making viewers enter the center of the system to watch 3D scene around them. The surrounded 3D scene provides viewers a feast of enhanced immersive experience. The light field principle, rendering algorithm, selection of viewing area and experi- mental results are discussed in the letter, showing the potential of being an all-around-type immersive 3D display by employing more projectors.
An optimization method is proposed for designing an LED freeform lens which produces a uniform circular pattern with high energy efficiency.This method is composed of three main aspects:design of the initial guess,parameterization of the freeform surface,and construction of the merit function.The initial guess is created by solving an ordinary differential equation numerically.An approach of selecting optimization points is introduced for parameterization of the freeform surface.The merit function is constructed by use of the irradiance uniformity and the efficiency of the lens.Design examples are given,and the results show that the irradiance distribution is well controlled with a maximum uniformity(the relative standard deviation of irradiance,RSD) of 0.0122 and a maximum efficiency of 93.88%.This optimization method can be generalized to design freeform lenses with different lighting patterns or without rotational symmetry.
Peng LIU Reng-mao WU Zhen-rong ZHENG Hai-feng LI Xu LIU
