Liquid crystal displays (LCDs) with edge-lit backlight systems offer several advantages, such as low energy consuming, low weight, and high uniformity of intensity, over traditional cathode-ray tube displays, and make them ideal for many applications including monitors in notebook personal computers, screens for TV, and many portable information terminals, such as mobile phones, personal digital assistants, etc. To satisfy market requirements for mobile and personal display panels, it is more and more necessary to modify the backlight system and make it thinner, lighter, and brighter all at once. In this paper, we have proposed a new integrated LGP based on periodic and aperiodic microprism structures by using polymethyl methacrylate material, which can be designed to control the illumination angle, and to get high uniformity of intensity. So the backlight system will be simplified to use only light sources and one LGP without using other optical sheets, such as reflection sheet, diffusion sheet and prism sheets. By using optimizing program and ray tracing method, the designed LGPs can achieve a uniformity of intensity better than 86%, and get a peak illumination angle from +400 to -200, without requiring other optical sheets. We have designed a backlight system with only one LED light source and one LGP, and other LGP design examples with different sizes (1.8 inches and 14.1 inches) and different light source (LED or CCFL), are performed also.
As the size of diffracting structures with a diffractive optical elements is on the order of or less than the illumination
wavelength, it is necessary to use a rigorous electromagnetic theory of diffraction to accurately analyze its performance.
A rigorous electromagnetic analyse of two-dimensional diffractive microlenses is presented. Without paraxial
approximation, the focusing performance of diffractive microlenses with different f-number have been determined
including diffractive efficiency with different incidence polarizations (TE polarization and TM polarization), and
different profile structures (continuous profile, 8-level profile and 2-level profile) of mircolenses, respectively. Both
scalar and rigorous analyses are performed on all these diffractive microlenses.
An aperiodic two-dimensional diffractive optical element (DOE) with subwavelength features as an uniform beam shaper which shapes an input laser beam into an uniform intensity distribution in an observation plane has been designed. A rigorous design method combined an iterative optimization algorithm with a rigorous electromagnetic computation -- the finite-difference time-domain (FDTD) method has been proposed. The design method and the FDTD method have been discussed in detail. The simulated results have shown that the DOE designed by this rigorous method can produce an uniform field distribution with flat-top, steep edge and low profile error in an observation plane.
Axially symmetrical diffractive phase planes (DPPs) are easily fabricated and have been used in a variety of applications, especially for realizing uniform loop focal spot with steep side, flat top, flat side lobe and high efficiency. A kind of hybrid design algorithm combined ST algorithm and input-output algorithm is introduced for axially symmetrical DPPs design to realize uniform loop focal spot. The computer simulation has shown that the algorithm is robust and convergent. The DPPs has been designed to product uniform loop focal spot with high diffractive efficiency of the energy inside the loop spot, high uniformity for both main lobe and side lobe (both more than 96%), and steep side simultaneously.
By using a diffractive optical element (DOE), a new method to generate dark hollow laser beam (DHLB) is presented in this paper. The optimization theories to design the DOE can obtain a globally optimal solution in an exact analytic form. The generated DHLB shows good performances for actual applications, which testifies the validity of this new method.
We investigate the four-wave mixing (FWM) effect in a dispersion-managed transmission line. The dispersion-managed line consists of many repeated fiber spans, each of which includes a positive- and a negative-dispersion fiber. The analytical expression of the FWM is obtained. The influence of the channel spacing, the fiber spans’ number and the compensating dispersion parameter on the FWM effect is analysed. The dispersion-managed transmission line is optimized to depress the generated FWM noise.
An iterative optimization-based synthesis algorithm has been presented for the design of diffractive micro-optical elements (DMOE's) with subwavelength structures as beam controllers. The DMOE's with subwavelength structures only require single step fabrication, but the subwavelength and aperiodic nature of the DMOE's prevent the use of scalar diffraction theory and the use of coupled-wave theory. We apply the finite-difference time-domain (FDTD) method as the vector model and the iterative plane wave spectrum algorithm (IPWS) as the synthesis algorithm, which can make the design of DMOE's in reasonable time frames. The IPWS, the FDTD method, the plane wave spectrum propagation method have been discussed and a beam deflector with subwavelength structures has been designed.
With a Damman grating and an artificial neural network back-propagation network (BP network), a fast and parallel 3-D non-contact measurement method using a stereo vision system is introduced. Some detail discussions on optical setup, data acquisition and some method to raise the training precision of BP network are proposed. Experiments have been completed and the results proved the feasibility of the method. Using the method, one can get the object profile information rapidly, deal with data almost parallel and need not to consider the effect of lens distortion.
A novel hybrid phase-retrieval non-iteration algorithm combining random searching algorithm and simulated annealing algorithm has been proposed for designing the diffractive optical elements (DOE'S) used for producing a uniform focal spot required with top head, steep edge, low side lobe or concentrating high power performance in the main lobe. The continuous phase distribution of diffractive optical elements with a good geometrical structure has been obtained by the new hybrid algorithm. Starting the optimal process with a continuous phase profile and taking the special phase function, this new algorithm can construct fully continuous phase screens for tailoring far-field intensity profiles (beam shaping). The continuous phase distribution using the new algorithm will be fabricated easily , make the elements have high diffractive efficiency, heighten the threshold value resisting the high power laser and get the far-field intensity profile with high uniformity at the main lobe, very small side lobe and steep edge. The computer simulation has shown that the algorithm is robust and maintains the continuous phase distribution throughout the optimal process. The DOE'S with continuous phase have been designed with more than 99% energy efficiency, less than 1% side slobe non-uniformity, and, with more than 90% energy efficiency, less than 2% top non-uniformity, respectively.