LCD backlights,light sources,and flat fluorescent lamps

Abstract— Backlights are indispensable for the operation of LCDs. Light sources or lamps are the core components of backlights. There are many types of light sources for backlights such as cold cathode fluorescent lamps (CCFLs), external electrode fluorescent lamps (EEFLs), hot‐cathode fluorescent lamps (HCFLs), flat fluorescent lamps (FFLs), and light‐emitting diodes (LEDs). Recently, FFLs are becoming one the most interesting light sources for LCD‐TV backlights. Channel profiles and the structure of FFLs in more detail are discussed in this paper. The channel profile of FFLs with maximum brightness uniformity was designed, fabricated, and characterized. The FFL backlight demonstrated 10,500 nits and the total power consumption was 110 W at room temperature.     

Optimized LCD backlight for outdoor and high‐brightness applications

A high‐intensity backlight for use with large LCD panels has been developed. It supports the performance and environmental requirements of a display intended for outdoor applications. This backlight technology uses an inductively coupled electrodeless fluorescent lamp with a lifetime of 100,000 hours, instant starting at ?40°C and a stable light output over a temperature span of 70°C. The backlight design has been optimized for luminance uniformity and efficiency within a display depth of 6 in. A 21.3‐in. LCD monitor, using this backlight technology, provides an image brightness of 2000 cd/m² from a single 150‐W lamp.     

Electrical feedback control for driving mercury‐free flat fluorescent lamp

Abstract— Recently, a mercury‐free flat fluorescent lamp has been developed for LCD backlight application, utilizing a glow‐discharge mode instead of a discharge contraction. This paper proposes a lamp‐driving system with a feedback loop which prevents discharge contraction and stabilizes the operation of the lamp ignition and radiation. By measuring the current that flows through the lamp, the loop can adjust the current level to a normal operational level and suppress the long‐term excitation that causes discharge contraction. The proposed method has been verified by hardware experiments which are compared to that of a conventional open‐loop circuit by discharge contraction time and a change in luminance.     

Physical‐based photon mapping for an LED backlight lighting simulator

Abstract— Liquid‐crystal displays (LCDs) have become increasingly popular due to their lower price and larger sizes. In particular, backlights having an RGB LED source have recently attracted attention, because they have a wider color gamut, higher luminance, and lower power consumption. However, even when the backlight area is uniformly covered with light modules based on arrays of individual LEDs, this does not ensure a uniform chromaticity and luminance over the backlight panel, thereby stressing the need for lighting simulation of the backlight. Accordingly, this paper proposes an effective lighting simulator to predict the chromaticity and luminance distribution of an LED backlight panel for an LCD. First, the spectrum‐based photons are all initially generated using a random function with a constraint satisfying the spectral power distribution of the actual LED light sources, while their emitting directions are determined based on a pre‐calculated probability using a random variable angle. The optical characteristics of the inner sheets in the LCD backlight structure are then modeled using the wavelength and incident angle to predict the next direction of each photon based on the reflection and transmittance at an intersection. All the photons that reach the unit area of the outward panel are gathered to shape their spectral power distribution, then converted to CIEXYZ values and multiplied with a color‐matching function. Finally, a realistic image visualization of these CIEXYZ values is achieved through standardized device characterization using the sRGB mode. Experiments confirm that the proposed spectrum‐based photon mapping can effectively predict the chromaticity and luminance distribution of an LED backlight panel, providing a good lighting simulation of an LED backlight before manufacturing the LCD.     

A critical examination of perceptual and cognitive effects attributed to full-spectrum fluorescent lighting

Full-spectrum fluorescent lighting (FSFL) has been credited with causing dramatic improvements in vision, perception and cognitive performance as compared with other fluorescent lamp types. These effects are hypothesized to occur because of similarity between FSFL emissions and daylight, which is said to have evolutionary superiority over other light sources. This review, covering 1945-98, critically considers the evidence for these claims. In general, poorquality research has resulted in an absence of simple deterministic effects that can be confidently attributed to fluorescent lamp type. Promising avenues for lighting- behaviour research include investigations of cognitive mediators of lighting—behaviour relationships, and flicker rates and colour rendering effects on visual processing, appearance judgements and affect. Good lighting solutions are more complex than lamp type specification.     

A critical examination of perceptual and cognitive effects attributed to full-spectrum fluorescent lighting

Full-spectrum fluorescent lighting (FSFL) has been credited with causing dramatic improvements in vision, perception and cognitive performance as compared with other fluorescent lamp types. These effects are hypothesized to occur because of similarity between FSFL emissions and daylight, which is said to have evolutionary superiority over other light sources. This review, covering 1945-98, critically considers the evidence for these claims. In general, poor-quality research has resulted in an absence of simple deterministic effects that can be confidently attributed to fluorescent lamp type. Promising avenues for lighting behaviour research include investigations of cognitive mediators of lighting-behaviour relationships, and flicker rates and colour rendering effects on visual processing, appearance judgements and affect. Good lighting solutions are more complex than lamp type specification.     

基于单目视觉的助航灯具定位及发光口识别

为实现助航灯具的自动清洗,本文提出一种基于单目视觉的助航灯具及其发光口的定位和识别方法。通过提取摄像机画面中的灯具轮廓,采用最小二乘法拟合灯具不发光状态下的椭圆模型,得出灯具中心的像素坐标,采用质心法计算发光状态下光源中心的像素坐标。通过对摄像机的标定,建立地面约束坐标系,实现灯具像素坐标到世界坐标的转换,得到摄像机与灯具的相对位置。     

Spectroscopic analysis of the non‐circular external electrode fluorescent lamp for large‐sized LCD backlight applications

Abstract— The spectroscopic analysis of the external electrode fluorescent lamp (EEFL) having non‐circular cross sections was carried out in order to obtain insight into the discharge condition confined in this unusual discharge space. The emitting spectra of EEFLs with and without phosphor layers were investigated as a function of the measurement position and/or time. It was found that the argon (Ar) emission was intense when the lamp was turned on and decreased rapidly as the Hg emission lines got stronger. The intensities of visible lines from mercury atoms were measured as a function of position along the direction perpendicular to the channel axis. It was found that the positive column does not spread in the entire discharge space but was contracted at the center of the channel. This result was discussed in relation to the ionization process occurring in the low‐pressure discharge lamps. In addition, the correlation between the cross‐sectional shape and the backlight efficiency was investigated, from which optimized shape parameters could be derived.     

Étendue‐density homogenization lamps with light concentration function

Abstract— In order to increase the screen brightness of Digital Micromirror Device? projectors (DMD? projectors), we designed a new compact lamp. In our previous work, we discussed a lamp that has an aspherical lamp reflector and an aspherical front glass, which we called EHLa. Although EHLas improve the light convergence at the entrance of rod integrators, they require external lenses for light condensation. We, therefore, discuss a new EHLa that can converge light without the need for external lenses. The new lamp corresponds to conventional elliptic reflector‐type lamps, which are widely used for mobile‐type DMD? projectors. Our simulations demonstrated that the ratio of increased brightness is 17.1% for the new lamp design versus conventional lamps in a 0.7‐in.‐diagonal DDR DMD? panel.     

High‐efficiency light‐collection optics for lamp‐based projection TV

Abstract— A new light‐collection optics has been developed that enhances the luminance of projection TV which use lamps as the light source. The conventional optical system consists of an elliptical reflector and a flat‐surface front glass, but these systems cannot sufficiently collect the beams coming from the light source, and they cause loss in the coupling with the light pipe. To solve this problem, we devised a new optical system through a structure of an aspherical reflector and an aspherical front glass. This new optical system concentrates the beams coming from the light source to a smaller point which improves the coupling efficiency. Thus, we have successfully increased the luminance of the projection TV by approximately 10%. This paper reports the design principles of the new optical system and the results of a prototype experiment.     

《煤矿安全规程》电气部分修订意见

提出严禁矿用一般型照明灯具、通信、自动化装置和仪器仪表等小功率非防爆设备用于煤矿井下;照明灯具应采用LED等冷光源,优选本质安全型或本质安全型与浇封型或隔爆型等其他防爆型式的复合型;用于煤矿井下的监控、通信、监视、控制设备和仪器仪表应优选本质安全型,设备之间传输的信号必须是本质安全型信号;大功率电气设备应优选隔爆型电气设备,隔爆型电气设备应将接线腔与主腔分腔布置。提出矿用通信与信号电缆和光缆可以盘圈。提出与隔爆型电气设备连接的矿用电缆必须耐爆;严禁矿用通信与信号电缆和光缆直接与单一隔爆型电气设备连接;与隔爆兼本质安全型电气设备连接的矿用通信与信号电缆和光缆必须耐爆。提出煤矿井下严禁使用铝芯电缆。提出用于局部通风机的欠压保护和失压保护应有延时措施;除掘进、开拓和临时施工场所外,尽量减少局部通风机的使用;严禁在形成全风压通风的回采工作面使用局部通风机稀释上隅角瓦斯等。提出矿灯应采用LED等冷光源,应采用本质安全型或本质安全型与浇封型等其他防爆类型的复合型;光源及灯绳(电池与头灯分离时)中传输的电能必须是本质安全型;严禁白炽灯等特殊型矿灯用于煤矿井下。     

Holographic backlight unit for mobile LCD devices

Abstract— The commercial backlight unit for a portable liquid‐crystal display (LCD) device typically consists of several light‐emitting diodes (LEDs) as the light source, a couple of prismatic sheets and diffusers, and a guide plate for backlight optics. A simplified backlight unit for portable LCDs, merely consisting of a hologram‐imprinted light‐guide plate (H‐LGP) and one diffuser, is proposed in this paper. By employing H‐LGP, it is expected that several optical films essential to the conventional backlight unit can be eliminated. This paper aims to improve the optical efficiency of LGPs by deriving the design parameters of the H‐LGP and performing the related computations. The angular luminance distribution of the emanating light from H‐LGP has been measured and compared with the results obtained by simulation. A proper collimation is necessary in order to increase the luminance. The backlight developed through this work has high optical performance combined with low cost.     

LED backlight system with double‐prism pattern

Abstract— A LED backlight system with a double‐prism pattern for use in mobile phones to achieve thin and high luminance LED backlight systems is proposed. The double‐prism pattern is formed on the light guide of the proposed LED backlight system and simultaneously exhibited two optical functions: shifting of the light from the direction of the guided light toward the radiated light and controlling the directivity of the radiated light. Therefore, using the double‐prism pattern eliminates two prism sheets and a diffusive sheet, which are indispensable optical elements to exhibit the optical function that controls the directivity of light in conventional LED backlight systems. Consequently, the thickness of the proposed LED backlight system is reduced to 0.75 mm compared to that of the conventional system. A luminance of 3115 nits and a full‐width half maximum of 35° for radiated light, which are comparable to conventional LED backlight systems, were obtained.     

Optimal maintenance planning for sustainable energy efficiency lighting retrofit projects by a control system approach

The energy savings achieved by implementing energy efficiency (EE) lighting retrofit projects are sometimes not sustainable and vanish rapidly given that lamp population decays as time goes by if without proper maintenance activities. Scope of maintenance activities refers to replacements of failed lamps due to nonrepairable lamp burnouts. Full replacements of all the failed lamps during each maintenance interval contribute to a tight project budget due to the expense for the lamp failure inspections, as well as the procurement and installation of new lamps. Since neither “no maintenance” nor “full maintenance” is preferable to the EE lighting project developers (PDs), we propose to design an optimal maintenance plan that optimises the number of replacements of the failed lamps, such that the EE lighting project achieves sustainable performance in terms of energy savings whereas the PDs obtain their maximum benefits in the sense of cost–benefit ratio. This optimal maintenance planning (OMP) problem is aptly formulated as an optimal control problem under control system framework, and solved by a model predictive control (MPC) approach. An optimal maintenance plan for an EE lighting retrofit project is designed as a case study to illustrate the effectiveness of the proposed control system approach.     

Energy‐efficient liquid‐crystal displays (e2‐LCDs) using a photonic‐crystal backlight system

Abstract— Cholesteric liquid crystals automatically form one‐dimensional photonic crystals. For a photonic crystal in which light‐emitting moieties are embedded, unique properties such as microcavity effects and simultaneous light emission and light reflection can be expected. Three primary‐color photonic‐crystal films were prepared based on cholesteric liquid crystal in which fluorescent dye is incorporated. Microcavity effects, i.e., emission enhancement and spectrum narrowing, were observed. Two types of demonstration liquid‐crystal displays (LCDs) were fabricated using the prepared photonic‐crystal films in a backlight system. One is an area‐color LCD in which a single photonic‐crystal layer is used for each color pixel and the other is a full‐color TFT‐LCD in which three stacked photonic‐crystal layers are used as light‐conversion layers. The area‐color LCD was excited by using 365‐nm UV light, and the full‐color TFT‐LCD was excited by using 470‐nm blue LED light. Because of the photonic crystal's unique features that allow it to work as light‐emitting and light‐reflecting layers simultaneously, both LCDs demonstrate clear readable images even under strong ambient light, such as direct‐sunlight conditions, under which conventional displays including LCDs and OLED displays cannot demonstrate clear images. In particular, an area‐color LCD, which eliminated color filters, gives clear images under bright ambient light conditions even without backlight illumination. This fact suggests that a backlight system using novel photonic‐crystal layers will be suitable for energy‐efficient LCDs (e²‐LCDs), especially for displays designed for outdoor usage.     

Sphere‐supported thin‐film electroluminescence: A new platform technology for displays and lighting

Abstract— Currently, powder electroluminescence is used for low‐brightness flexible lamps offering durable plastic‐based lighting solutions principally for low‐ambient light conditions where lighting or backlighting is required. Sphere‐supported thin‐film electroluminescence (SSTFEL) promises dramatic new capability in both flexible lamps and displays owing to its high brightness and long‐life capability. SSTFEL is based on robust thin‐film phosphors deposited on spherical ceramic dielectric particles which are embedded in a thin plastic sheet. A printing approach permits versatile, low‐cost manufacturing of patterned SSTFEL devices and eliminates the need for high‐temperature substrates.     

A novel diffractive backlight concept for mobile displays

Abstract— Power‐efficiency demands on mobile communications device displays have become severe with the emergence of full‐video‐capable cellular phones and mobile telephony services such as third‐generation (3G) networks. The display is the main culprit for power consumption in the mobile‐phone user interface and the backlight unit (BLU) of commonly used active‐matrix liquid‐crystal displays (AMLCDs) is the main power drain in the display. One way of reducing the power dissipation of a mobile liquid‐crystal display is to efficiently distribute and outcouple the light available in the backlight unit to direct the primary wavelength bands in a spectrum‐specific fashion through the respective color subpixels. This paper describes a diffractive‐optics approach for a novel backlight unit to realize this goal. A model grating structure was fabricated and the distribution of outcoupled light was studied. The results verify that the new BLU concept based on an array of spectrum‐specific gratings is feasible.     

Adjustable beam lighting with LED matrix and lens array

An adjustable beam lighting solution is coming widely on demand for different applications with improved energy efficiency, reduced light pollution, or enriched decorative effects. A Matrix Lighting configuration, which mainly consists of a light‐emitting diode matrix and a lens array, is proposed as a promising adjustable beam lighting solution. It easily builds up the source‐target mapping based on the integral imaging principle, and it could adjust the light beam and shape freely and timely. The basic configuration, the general design rules with imaging optics, and the optimization approaches based on ray tracing were presented. An example lighting system consists of a 32 × 32 × RGB light‐emitting diode matrix, and the 8 × 8 Fresnel lens array is demonstrated, which accomplishes a localized lighting with addressable regions for power saving. It can also project colorful patterns on the ground or a wall for atmosphere heightening.     

Development of a dual‐lamp projector with higher brightness

Stationary projectors mainly used in system applications have recently gained a wider application range, including general presentations in halls and large conference rooms and being used, for example, in digital signage and for monitoring purposes. Consequently, they are required to meet new market demands for durability, reliability, and flexibility in installation in addition to their conventional basic performance such as especially high brightness. To achieve especially high brightness, a new optical system with two lamps is proposed; the profile of the cover glass that prevents the glass from scattering is made aspherical, the profile of the beam‐combining mirror is improved with its position optimized, and the size of the incident plane of the integrator rod is made larger (1.1 times). These measures resulted in an optical system of an even higher efficiency with 7000 lm, which is the highest in its class (according to a June 2010 investigation). Also, the arrangement of two parallel lamps completely eliminated the effect of heat passing from one lamp to the other, which helped secure durability, reliability, and flexibility in installation. Furthermore, the combined use of the unique non‐telecentric optical system, adopted from the conventional single‐lamp model, helps maintain the class‐highest contrast ratio.^1,2