Switchable helical holographic structures

Abstract— A 3‐D array of helical structures fabricated using holographic polymer‐dispersed liquid crystals (H‐PDLC) is presented. Multiple coherent beams are interfered to create a constructive helical pattern which is permanently captured using the standard H‐PDLC method. Films with such array of helical structures have both diffractive and circular polarization sensitive reflective properties. Iso‐intensity patterns, design parameters, fabrication process, optical/electro‐optical performance of these periodic helical structures are discussed along with their potential application for advanced electro‐optical devices.     

Nanoparticle‐embedded polymer‐dispersed liquid crystal for paper‐like displays

Abstract— A polymer‐dispersed liquid‐crystal (PDLC) matrix template embedded with nano/microparticles can be backfilled/infiltrated with a dye‐doped liquid crystal for a paper‐like reflective display. In this way, a desirable degree of diffusion can be realized to reduce the viewing‐angle dependency of a gain reflector and metallic glare without changing other electro‐optical properties.     

Light‐scattering liquid‐crystal composites with reduced off‐axis haze

Abstract— The majority of liquid‐crystal (LC) composites operating in a light‐scattering mode suffer from scattering of the obliquely incident light in the field on‐state (off‐axis haze effect). This is evident in the angularly selective viewing‐angle characteristic with a maximal transmittance corresponding to the normally incident light. We consider methods to control the viewing‐angle characteristic of polymer‐dispersed LC (PDLC) and filled LC. For PDLC samples, this control is realized by modification of the refractive index of the polymer matrix with highly refractive nanoparticles (NP) having a low rate of aggregation in the polymer. By proper optimization of NP concentration, one can bring the refractive index of the polymer matrix in the range needed to reduce the haze problem. In filled LC, the viewing‐angle curve depends on the refractive‐index mismatch between the LC and NP. By optimization of this parameter, one can flatten the angular characteristic or obtain selectable viewing angles in the desirable range. These results allow for the construction of optical shutters and a scattering‐type LCD with controllable viewing‐angle characteristics, particularly with low off‐axis haze.     

Time‐multiplexed color image generation by viewing‐zone scanning holographic display employing MEMS‐SLM

The viewing‐zone scanning holographic display, which can enlarge both screen size and viewing zone, is modified to enable color image generation by using the time‐multiplexing technique; R, G, and B lasers sequentially illuminate a single microelectromechanical systems spatial light modulator with a high frame rate. The viewing‐zone scanning system enlarges screen size by using a magnifying imaging system and generates a large number of reduced viewing zones that are aligned in the horizontal direction by a horizontal scanner to enlarge the viewing zone. The interval of the reduced viewing zones is set to be one‐third of the width of the reduced viewing zones or less so that three sets of reduced viewing zones are generated corresponding to the three colors. Color image generation was demonstrated for a screen size of 2.0 in. and a viewing zone angle of 40.0°.     

Birefringent light‐shaping films for mini‐LED backlights

Birefringent light‐shaping films (BLSFs) for mini‐LED backlit liquid crystal displays (LCDs) are proposed and experimentally demonstrated by passive polymer‐dispersed liquid crystal (PDLC) films. Such films show angle‐selective scattering properties, achieved by proper material engineering and good vertical alignment of liquid crystals. They only respond to angles rather than spatial locations. By directly adhering the BLSF onto a LED, the angular intensity distribution of light can be tailored from Lambertian‐like to batwing‐like. Further simulation proves that by engineering the angular distribution, a fewer number of LEDs or equivalently a shorter light‐spreading distance is required to maintain good uniformity. These BLSFs are expected to find widespread applications in emerging mini‐LED backlit LCDs and shed light on designing other light‐shaping films in the future.     

The color properties of a reflective CMYK module using polymer‐dispersed liquid crystal (PDLC)

A reflective CMYK (cyan, magenta, yellow, and black) module using polymer‐dispersed liquid crystal (PDLC) is investigated for multi‐color reflective display. Combined with the electro‐optical properties and visible spectral reflectivity of PDLC films, the color properties of the reflective CMYK module were evaluated in terms of the Uniform Color Space‐CIE 1976 L*a*b*. It is found that the blue light reflectivity of the PDLC films is lower than green light and red light reflectivity. With the increase of the voltage applied on PDLC, the color lightness of the CMYK module generally decreases, while the color saturation increases. When the voltage changed from 0 to 70 V with a 5‐V change amplitude, modules C, M, Y, and K severally exhibit at least five, six, three, and seven colors.     

Viewing‐angle‐switching device based on array of optical micro‐rods incorporated with electrophoretic material systems

We have successfully demonstrated a control device for a viewing angle that enables switching between two states, a wide‐viewing angle, and a narrow‐viewing angle. It is composed of a light‐transmitting portion formed with an array of optical micro‐rods and a shielding/transmitting changeable portion of cross stripes designed with electrophoretic material systems consisting of black particles and an optically transparent medium. When the black particles are fully dispersed in the optically transparent medium, the cross stripe portion plays the role of a non‐transmitting material as the shielding portion in a similar manner to a conventional viewing angle control film. When the black particles are completely gathered electronically to one side in the optically transparent medium, in contrast, the cross stripe portion filled by the optically transparent medium can transmit incident light. These functions allow us to select electrically either of two modes between a limited viewing angle and a non‐limited viewing angle. The optical properties for the limited viewing angle mode were +/?30° of the visible angle and 50% of the transmittance, and the one for the non‐limited viewing mode was 58% of the transmittance. The response time from the narrow‐viewing angle to wide‐viewing angle was 1 s at 20 V of applied voltage.     

Application‐specific integrated filters for color‐sequential microdisplay‐based projection applications

Abstract— Application‐specific integrated filters (ASIFs), based on a unique holographic polymer‐dispersed liquid‐crystal (H‐PDLC) material system offering high efficiency, fast switching, and low switching voltage, are being developed for microdisplay‐based projection applications. The basic properties and key benefits of ASIFs in projection displays are reviewed.     

Patterned liquid‐crystal laser film for multi‐dimensional multi‐color emissive film technology

Abstract— A two‐dimensional array consisting of dye‐doped reflection‐mode holographic‐polymer‐dispersed liquid crystal (H‐PDLC) lasers with alternating pitch lengths is presented. These post structures each reflect at a narrow bandwidth of light. The addition of laser dye to the H‐PDLC system allows for the generation of laser emission at the edge of the reflection band, or photonic band gap. In patterning these H‐PDLC post structures, a narrow‐linewidth patterned emissive color film is realized. The potential of such films and their implication in the display industry is discussed. In creating a three‐color array, an active emissive color film could replace the backlight and color filter components within the display. Such a patterned system would possess a wide color gamut, through spatial color synthesis, formed by narrow‐linewidth lasing structures with well‐defined wavelengths of emission.     

Optical characterization of OLED displays

Multispectral viewing angle and imaging characterization have been applied to different organic light‐emitting diode (OLED) displays. Angular dependence of the OLED emission is always complex because of its multilayer structure. Spectral information is also related to the geometry of Fabry–Perot‐like structure of each OLED. High‐resolution viewing angle measurements of different OLED displays are reported and compared. Multispectral viewing angle polarization properties are also reported. Imaging measurements allow to detect wavelength shift on the surface of the displays probably related to thickness non‐uniformities. Local radiance fluctuations from one pixel to the other more related to driving problems due to the dispersion of the electric properties of the driving thin‐film transistors are also detected.     

A viewing‐angle‐controllable blue‐phase liquid‐crystal display

Abstract— A viewing‐angle‐controllable liquid‐crystal display (LCD) is proposed. When the device is only driven by an in‐plane electric field, it exhibits a wide‐viewing‐angle (WVA) mode. And it exhibits narrow‐viewing‐angle (NVA) mode when it is driven by a vertical electric field as well as an in‐plane electric field. In this manner, the viewing angle of the device can be controlled from 100° to 30°. The device exhibits a good viewing‐angle‐controlling characteristic and high transmittance.     

A perceptually based metric to characterize the viewing‐angle range of matrix displays

Abstract— The current specification of a display's viewing angle as the angle within which the contrast ratio is larger than 10:1 appears not to be predictive for the acceptable viewing‐angle range obtained from perception experiments. In our search towards a perceptually relevant specification for the viewing angle, the physical characteristics of the display that are most related to the viewing‐angle‐dependent image quality were analyzed. This was done for two types of liquid‐crystal displays and one plasma TV. The results indicate that a combination of the luminance and chromaticity coordinates of the higher gray levels predicts the degradation in image quality as a function of viewing angle. As a consequence, a new definition of a display's viewing‐angle range is proposed based on these characteristics.     

Deformed nanostructure of photo‐induced biaxial cholesteric films and their application in VA‐mode LCDs

Abstract— Novel biaxial retardation films made from photo‐induced deformed cholesteric liquid‐crystal (LC) nanostructures using reactive mesogen mixtures (RMMs) for a viewing‐angle compensation of vertically aligned liquid‐crystal displays (VA‐LCDs) was developed. The deformed cholesteric LC nanostructure has been observed by X‐ray‐diffraction (XRD) measurement. The birefringence of the film was described well by our optical model based on a form birefringence theory. The VA‐LCDs with photo‐induced biaxial cholesteric films have excellent viewing‐angle properties.     

A continuous‐viewing‐angle‐controllable liquid‐crystal display using a blue‐phase liquid crystal

Abstract— A continuous‐viewing‐angle‐controllable liquid‐crystal display (LCD) using a blue‐phase liquid crystal is proposed. To realize both wide‐viewing‐angle (WVA) mode and narrow‐viewing‐angle (NVA) mode with a single liquid‐crystal panel, each pixel is divided into a main pixel and a subpixel. The main pixel is for displaying images in both modes. The subpixel is for displaying images in WVA mode and controlling the viewing angle in NVA mode. The device exhibits a good viewing‐angle‐controlling characteristic and high transmittance.     

环氧基聚合物分散液晶膜的制备及其性能研究

采用聚合相分离方法制备环氧树脂基PDLC膜.通过对液晶含量、固化温度和时间等条件进行优化,研究上述条件对PDLC膜性能的影响;使用UV-Vis、AFM、SEM等方法对聚合物的物理特性和PDLC膜的光电性质做了深入探讨.PDLC膜在传感器、光电开关、光栅以及新型分析仪器元器件等方面具有广阔的应用前景.     

新型集成聚合物波导/ 聚合物分散液晶光子射频移相器的设计

可控光子射频移相器是光控相控阵中的关键器件,本文用分立元件组成了光子射频移相器系统,对相移角度进行了测试,提出了一种新型的单片集成聚合物波导/聚合物分散液晶光子射频移相器的设计思想,介绍了移相器的制作工艺,分析了该移相器的优点.     

Dual-view holographic AR display based on Bragg mismatched reconstruction of the holographic optical element

A method for dual-view holographic display based on Bragg mismatched reconstruction of holographic optical element (HOE) is proposed. Under the Bragg mismatched condition, the reconstructed images are guided into two separated viewing zones to realize dual-view holographic display. Meanwhile, the viewing angle of each perspective is increased to 11.2°, which is almost 2.5 times as large as the traditional holographic display system. The design process of HOE is simple only by interference of plane reference wave and converging spherical signal wave, which has high practicability. Furthermore, the HOE can mix the virtual 3D image with real-world scenes, which could implement augmented reality (AR) display. Experiments validate that the proposed system can achieve dual-view holographic AR three-dimensional (3D) display with accommodation effect.     

Viewing angle switchable blue‐phase liquid crystal display with low voltage and high transmittance

We propose a viewing angle switchable blue‐phase liquid crystal display with low voltage and high transmittance. In this device, in‐plane protrusions are used to lower operating voltage and improve the transmittance. Besides, the top electrode can control viewing angle of the proposed display. When no voltage is applied to the top electrode, the display shows wide viewing angle mode. On the contrary, this display shows narrow viewing angle mode. So, this device exhibits low operating voltage, high transmittance, and good viewing angle controllable characteristics.     

Improvement of off‐axis color shift on hybrid viewing‐angle device using dual γ‐voltage method

We have mass production on one kind of liquid crystal display (LCD) device with hybrid viewing‐angle (HVA), which can be switched between the wide viewing‐angle (WVA) and narrow viewing‐angle (NVA) by one button. This device adopts the single cell design that with lower cost, and utilizes the optical properties of electrically tilted LC to achieve the function of NVA display. An issue has received less attention in the past and been indeed found in the production process. It is that the off‐axis color shift will appear in NVA mode. We put forward one method to improve this issue here, which is combined with the concepts of Gray Frame Insertion (GFI) and Impulse‐type driving. By switching the voltage between two different γ values, the color shift will be perfected on the produce.     

An integral‐imaging three‐dimensional display with wide viewing angle

Abstract— The viewing angle and flipping areas of a conventional integral‐imaging three‐dimensional (3‐D) display were analyzed. The pitches of the elemental image and micro‐lens are identical. The more micro‐lenses used, the smaller the viewing angle becomes and the wider the flipping areas become. In this paper, an improved integral‐imaging 3‐D display is presented. The pitch of the elemental image is larger than that of the micro‐lens. The single‐viewing angles of all micro‐lenses converge and there are no flipping areas at the optimal viewing distance. Computational reconstructions of improved and conventional integral imaging were carried out, and experimental results demonstrate that improved integral‐imaging 3‐D displays have a wider viewing angle than the conventional ones and do not have flipping areas at the optimal viewing distance.