An efficient design method based on the vector diffraction theory is presented for high numerical aperture achromatic imaging lenses (HADLs). Simultaneously achieving high numerical aperture and achromatic performance puts extremely demanding requirements on the design of HADLs. Therefor an efficient numerical technique is devised by combining the finite-difference time-domain (FDTD) method with improved binary search algorithm and thus sets up a routing to facilitate the smooth connecting between vector diffraction computing with optimizing iteration. Furthermore by taking advantage of lens symmetry when optimizing the phase transmission function, tremendous computational resources saves. By taking advantage of FDTD rigorous electromagnetic computing and choosing carefully parameters, search strategy and objective function, optimal solution is obtained and the search time is very short. To validate the proposed method, a HADLs with focal length f=3.5um and numerical apertures (NA) of 0.753 is designed and focusing efficiency of over 30% across the visible light wavelength is obtained by numerical evaluation. A brief comparing with scalar diffraction theory is also carried out.
A spatial light modulator based on sub-wavelength gold grating structure, named GLCoS by us, has been devised and tested to meet the challenge of the high space-bandwidth product in holographic video display. A sample GLCoS has been made and its display color appears green. However, if it is to be a device of a display system, its color characteristics must be further investigated, that is, its ability to display RGB color and its color purity. There are two MIM (Metal-Insulator-Metal) in the GLCoS, sub-wavelength gold grating plus liquid crystal cell and aluminum electrode forms a hybridized MIM and sub-wavelength gold grating itself is a MIM acting as an open-end TM-FP (TM-Fabry-Pérot) resonator. Based on our previous study involving GLCoS theoretical model, simulation software platform (FDTD plus CST Studio Suite) and an experimentally verified sample of single color, we seek an engineering way with simplicity and compatibility in the sense of the technique to investigate the red-green-blue (RGB) color display with GLCoS. Among the huge parameter space including the geometry and size of the structure, material, wavelength and light incident angle. We choose to change width of the slit, incident angle, LC (liquid crystal) birefringence to find the appropriate GLCoS spectral characteristics. The simulation results show that the dynamic modulation of the RGB phase can be achieved in the visible light band, and its amount of phase modulation is close to 2π and high chromatographic purity.
The pickup mode of 3D scene in integral imaging (II) consists of parallel pickup, convergent pickup and off-axis pickup. Combining the advantages of parallel pickup and convergent pickup, a method for off-axis pickup is proposed. In fact, the depth of field (DOF) of the II is not only affected by various parameters in the display process, but also seriously affected by pickup process. We deduce the parameters that affect the DOF during the pickup process through theoretical analysis. In the modeling software C4D (Cinema 4D) the experiment is carried out. The results show that off-axis method is better, and verify the correctness of the calculation formula of DOF from the pickup process.
A deep sub-wavelength metal grating is used to replace the top electrode of liquid crystal on silicon (LCOS) to form a new structure of liquid crystal (LC) phase spatial light modulator (SLM), which to meet large spatial bandwidth product of dynamic holographic video display. Although the structure of this (gold) deep sub-wavelength grating-LC-metal electrode is similar to the geometry of the current LCOS, the physical mechanism is completely different, which we called it G-LCOS. In order to study the feasibility of the new G-LCOS for phase modulation of digital holographic display, based on previous calculation and simulation, we fabricate deep sub-wavelength gratings by using EBL and obtain a conceptual verification device by referring to the traditional LCOS process flow. In this paper, we present experimental investigations based on Michelson's interference principle on the phase modulation performance of this proof-of-concept device. The results show that the phase modulation of the structure can reach 1.2π. The slight disagreement between the theoretically predicted and the experimentally measured values for the G-LCOS phase modulation could be caused by the errors in the preparation process and measurement.
The optical properties of conventional optical components vary with wavelength. This leads to chromatic aberrations of optical components, and affects the accuracy and effectiveness of optical systems operating in wideband severely, especially in the visible band. The traditional optical design achieves achromatic result by bonding a plurality of lenses of different dispersion properties. The diffractive optical element (DOE) is characterized by miniaturization and light weight, which can realize functions such as array, integration, and arbitrary wave-front conversion. However, it is difficult to perform in conventional optical devices. In this paper, we can use diffractive lenses to achieve achromatic effects. A method of designing multi-wavelength achromatic lenses by using genetic algorithms combined with scalar diffraction theory is proposed. We use the focusing performance of different light wavelengths in the focal plane as the optimization condition. After several iterations, we finally get the optimal lens structure, and use this lens to do the simulation focusing experiment based on RGB three-color light. The simulation results show that the achromatic lens can focus the red, green and blue light to a point in space. In addition, the achromatic lens can be on the order of microns in diameter. Therefore, such a lens has a smaller volume, which is difficult to achieve with conventional lenses.
The challenge of dynamic holographic video display based on spatial light modulator is that it requires a large spatial bandwidth product. A simple method is to reduce the size of a single pixel in conventional LCOS (liquid crystal on silicon , LCOS) device. However, with the pixel size shrinks, it also requires a corresponding reduction in thickness of liquid crystal cell, otherwise the fringe field effect between pixels will affect the modulation of normal pixel. A deep sub-wavelength metal grating with a Fabry-Perot resonance is used instead of the top electrode of LCOS to form a liquid crystal phase modulator in this paper. Different from traditional LCOS, which realizes the phase modulation by using the birefringence of the liquid crystal in liquid crystal cell, the birefringence of the liquid crystal in our device is used to modulate the conditions of the reflective boundary of the deep sub-wavelength metal grating, which in turn controls the amount of phase modulation of reflected light in grating slit. The TechWiz and CST Microwave Studios software are used in this paper. Observing the distribution of liquid crystal directors and electric field distribution. Recording the intensity of visible light reflection and observing whether the device can achieve phase modulation of 0 ~ 2π by changing the pixel pitch and grating structure parameters. The simulation results show that there is no significant change in the liquid crystal directors and electric field distribution in different pixel pitch, the device phase modulation is close to 2π , and it has a high reflectivity.
KEYWORDS: Video, Video coding, Video acceleration, Computer programming, LCDs, Video compression, 3D displays, Image resolution, 3D video compression, Video processing
3D display requires a high-resolution, high-pixel playing system. This paper studies the video playback with single frame resolution of 16K × 8K . The bandwidth of display exceeds the current video display capability of 8K × 4K resolution. On the one hand, an appropriate system architecture needs to be built on the existing hardware level. 16 liquid crystal displays (LCDs) are used in this paper, with resolution of each LCD is 4K × 2K and size is 15.6 inches. Constituting a video display terminal array of 4 × 4 ,which the resolution is 16K × 8K . And a single-layer architecture with a fully decode is used. Decoding 16 channels of 4K signals on one host with i7-6800K and two video cards with NVS810 (both with 25GBps memory bandwidth) and deliver signals through 16 DP interfaces in parallel. On the other hand, under this architecture, running load of CPU and GPU, bus bandwidth and scheduling of dynamic storage capacity impose higher requirements on the encoding and decoding of video data. Comparative research between MPEG series and H.26X series coding standard has carried out in this paper. An inter-frame-based forward prediction (BFP) method is proposed. Finally, in the Win7 system, using mpeg-2 encoding standard, and decoding by using ffplay that achieves 16K video with 15Fps smooth playback. The effectiveness of the proposed method is verified. The proposed BFP method further reduces the decoding complexity of CPU.
Lens-array based imaging system is a kind of the direct-view system that is currently a hot topic of research. In fact, the viewing parameters of this system have been one of the focuses of research since its invention. However, most current literature discussions are based on depth of field, spatial resolution, and field of view. Only a few documents or products use angular resolution, spatial resolution, and field of view as criteria. The angle resolution is one of the parameters in the human eye vision module. This article will try to discuss the hardware conditions for realizing the angular resolution in the LCD discrete pixel system and its influence on the 3D perception. The results show that the angular resolution is determined by the number of pixels in each sub-image and is proportional to the number of elemental images and is limited by the LCD pixel pitch.
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