Advances in the light field displays based on integral imaging and holographic techniques(Invited Paper)

Light field displays comprise three-dimensional （3D） visual information presentation devices capable of providing realistic and full parallax autostereoscopic images. In this letter, the recent advances in the light field displays based on integral imaging （II） and holographic techniques are presented. Several advanced approaches to demonstrate the light field displays including viewing angle enhancement techniques of the II display, a fast hologram generation method using graphics processing unit （GPU） and multiple WRPs, and a holographic microscopy to display the living cells are reported. These methods improve some important constraints of the light field displays and add new features.

Integral imaging-based tabletop light field 3D display with large viewing angle

Light field 3D display technology is considered a revolutionary technology to address the critical visual fatigue issues in the existing 3D displays.Tabletop light field 3D display provides a brand-new display form that satisfies multi-user shared viewing and collaborative works,and it is poised to become a potential alternative to the traditional wall and portable display forms.However,a large radial viewing angle and correct radial perspective and parallax are still out of reach for most current tabletop light field 3D displays due to the limited amount of spatial information.To address the viewing angle and perspective issues,a novel integral imaging-based tabletop light field 3D display with a simple flat-panel structure is proposed and developed by applying a compound lens array,two spliced 8K liquid crystal display panels,and a light shaping diffuser screen.The compound lens array is designed to be composed of multiple three-piece compound lens units by employing a reverse design scheme,which greatly extends the radial viewing angle in the case of a limited amount of spatial information and balances other important 3D display parameters.The proposed display has a radial viewing angle of 68.7°in a large display size of 43.5 inches,which is larger than the conventional tabletop light field 3D displays.The radial perspective and parallax are correct,and high-resolution 3D images can be reproduced in large radial viewing positions.We envision that this proposed display opens up possibility for redefining the display forms of consumer electronics.

Power consumption in a field emission panel

The power consumption and electric field distribution in a field emission display （FED） panel is optimized with a novel pixel structure. A circuit model is proposed to estimate the total power consumption in an FED panel which is composed of anode energy consumption, energy loss due to the leakage current and the energy dissipated in the parasitic capacitances. Moreover, the parasitic capacitances play a vital part in the power consumption and driving performance. In order to lower the parasitic capacitances, multiple dielectric layers are used as the gate electrode. Due to different etching speeds, a novel pixel structure is formed. As a result, the power consumption of an FED panel is reduced by 28% in a full white picture, and the electron beam performance is also better than that of the conventional structure.

New type gate electrode of CNT-FED fabricated by chemical corrosive method

To obtain a triode structure canbon nanotube field emission display （CNT-FED）, the glass plate which contains a glass channels matrix is designed and used as the triode part of the CNT-FED. Normally, the gate electrode can be fabricated with screen printing methods and a channels matrix can be fabricated by two- faced chemical corrosion. By adjusting the etch time and the concentration of acid in the process, different shapes of the tunnels can be obtained. The size and morphology of channels are observed by a scanning electron microscope （SEM）, and the ingredients of the corrosion solution are detected by infrared ray （IR） analysis. Voltage is added to the triode structure for obtaining the brightness image of the spot on the screen. Eventually, the electron trace pulling from cathode to anode under an electric field is obtained by simulation. It is concluded that the simulation results accord with the experimental results which realize the optimized triode structure.

Light field head-mounted display with correct focus cue using micro structure array

A new type of light fiehl display is proposed using a head-mounted display （HMD） and a micro structure array （MSA, lens array or pinhole array）. Each rendering point emits abundant rays from different directions into the viewer＇s pupil, and at one time the dense light field is generated inside the exit pupil of the HMD through the eyepiece. Therefore, the proposed method not only solves the problem of accommodation and convergence conflict in a traditional HMD, but also drastically reduces the huge data in real three-dimensional （3D） display. To demonstrate the proposed method, a prototype is developed, which is capable of giving the observer a real perception of depth.

360° light field 3D display system based on a triplet lenses array and holographic functional screen

A 360° light field 3D display system is presented, which consists of a liquid crystal display, a novel triplet lenses array, and a holographic functional screen （HFS）. The mapping relationship among pixels, 3D objects, and view- ing positions are investigated. The aberration analysis of the single lens is carried out both in the simulation and the experiment, which shows that it cannot provide an excellent 3D image to the viewers. In order to suppress the aberrations, ＂the primary aberration theory＂ and ＂the damped least-squares method＂ are used for optical analysis and lens design. A 3D image with aberration correction can be viewed around the proposed display system.

金刚石薄膜场致发射的研究

简要分析了 FED场发射显示器的工作原理 ,陈述了非晶金刚石薄膜特殊的优点后 ,对用金刚石薄膜制作场发射器的可行性进行了讨论 ;还介绍了利用金刚石薄膜和阳极选择的方法对Spindt FED作了改进 ,从而使平面 FED更容易实现。

Field emission digital display tube with nano-graphite film cathode

The field emission digital display tube with a nano-crystalline graphite cold cathode is designed and fabricated. Under the control of the driving circuits, a dynamic digital display with uniform luminance distribution is realized. The luminance of the character segments is 190 cd/m2 at the operating voltage of 900 V. And the stable emission is attained with a fluctuation of about 3% at an average segment current of 75 μA. The results demonstrate that nano-crystalline graphite film is a promising material for cold cathode.

INFLUENCE OF ELECTRICAL AND STRUCTURAL PARAMETERS ON THE PERFORMANCE OF THE SPACERS IN HOPFED

The HOPping Field Emission Display （HOPFED） is a new architecture for field emission displays. The main difference between a conventional Field Emission Display （FED） device and a ItOPFED lies in the spacer structure. In a HOPFED, two dielectric plates, named hop and flu spacer, are sandwiched between the emitter and the front plate. The objective of this spacer structure is to improve the performance oF a FED substantially with notable contrast, color purity and luminance uniformity. In order to optimize the structure of the device and to make the electron spot on the screen match the requirement of the phosphor dot dimension, the influence of electrical and structural parameters of the device on the electron spot profile was studied by numerical simulation in this paper. Monte Carlo method was employed to calculate the potential distribution inside hop and flu spacers due to secondary electrons mechanism plays an important role in HOPFED. The results indicated that the potential distribution in the spacers and spot profile depended strongly on the hop voltage, anode voltage and spacer＇s layout. This study may provide a useful theoretical support for optimizing the structure in HOPFED.

Carbon-Nanotube-Based Normally-on-Driving Under-Gate Field Emission Display Panel

A carbon-nanotube-based normally-on-driving under-gate field emission display(FED)panel and its operation principle are presented.In this panel,field emission electrons are extracted directly from the cathode by the high anode voltage.The image is realized by modulating the voltage of under-gate,whose value is less than the cathode voltage,to stop the cathode producing field emission electrons.The electric field inside the emission region is calculated by the finite element method.The emission property of the cathode is also studied by numerical calculation method.The results indicate that a uniform and large emission area can be obtained in this new under-gate FED panel.This study provides powerful theoretic support for the feasibility of this new kind of under-gate FED panel.

Carbon nanotube emitters and field emission triode

Based on our study on field emission from multi-walled carbon nanotubes （MWNTs）, we experimentally manufactured field emission display （FED） triode with a MWNTs cold cathode, and demonstrated an excellent performance of MWNTs as field emitters. The measured luminance of the phosphor screens was 1.8 × 10^3 cd/m^2 for green light. The emission is stable with a fluctuation of only 1.5% at an average current of 260 μA.

Seeking new,ultra-narrow-band blue emitting phosphors with high color purity for wide color gamut displays

Ultra-narrow-band phosphors have gained widespread applications in lighting and displays to enhance brightness and improve color saturation.Typical phosphor designs employ UCr_(4)C_(4)-type compounds and designing new narrow-band phosphors with high color purity is a major challenge.Here,we explored a Eu^(2+)-doped Ba_(5)GeO_(4)Br_(6)phosphor,showing a narrow-band blue emission(λ_(em)=436 nm) excitation at the near-ultraviolet light with a full width at half maximum of 30.7 nm and high color purity of 96.6%.In addition,attractive cathodoluminescence characteristics were systematically analyzed by varying filament current(30-70 mA) and accelerating voltage(3-7 eV).Robust anti-degradation behavior and color point stability under continuous electron beam bombardment were confirmed.Given its excellent performance in photoluminescence and cathodoluminescence,application in wide color gamut displays appears promising.Using commercial phosphors β-SiAlON:Eu^(2+)and K_(2)SiF6:Mn^(4+)as green and red light co nverte rs respectively,and the title phosphor as the blue light converters,the fabricated w-LED exhibits a wide color gamut of 82% NTSC.