Mercury‐free 18‐in. flat fluorescent lamp with good uniformity

We have developed an 18‐in. 287 × 359‐mm flat fluorescent lamp (FFL) that uses a xenon dielectric barrier discharge and analyzed its electro‐optical characteristics. The surface luminance of the lamp having a diffuser sheet thickness of 3 mm was 5600 cd/m² and the luminance uniformity was 92% at an applied voltage of 950 Vrms. The luminous efficacy of the FFL was 24.5 lm/W for a luminance of 4200 cd/m² when driven by a sine‐wave voltage.     

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.     

Invited Paper: UHP‐lamp systems for projection applications

Abstract— Projection systems have found widespread use in conference rooms and other professional applications during the last decade and are now entering the home‐TV market with considerable pace. Projectors as small as about one liter are nowadays able to deliver a screen flux of several thousand lumens and are, with a system efficacy of more than 10 lm/W, the most‐efficient display system realized today. Because such highly efficient projectors employ microdisplays as light valves, short‐arc lamps are a key component in realizing these properties. The introduction of the UHP‐lamp system by Philips in 1995 can be identified as one of the key enablers for the commercial success of projection systems. The ultra‐high‐performance (UHP) lamp concept features outstanding arc luminance, a well‐suited spectrum, long life, and excellent flux maintenance. For the first time, it combines a very‐high‐pressure mercury‐discharge lamp having an extremely short and stable arc length with a regenerative chemical cycle that keeps the discharge walls free from blackening, leading to lifetimes of over 10,000 hours. In this review, the most important aspects of the UHP concept that enabled its success in the projection market are described, followed by a discussion of some recent additions to the UHP‐product portfolio.     

Mercury‐free 18‐in. flat fluorescent lamp with good uniformity

Abstract— We have developed an 18‐in. 287 × 359‐mm mercury‐free flat fluorescent lamp (FFL) having a new structure that utilizes dielectric barrier discharge and contains pure xenon gas. The electro‐optical characteristics have been analyzed. The surface luminance of the lamp having a diffuser sheet is 5600 cd/m² and the luminance uniformity is 92% at an applied voltage of 1050 Vrms and an applied frequency of 20 kHz in the form of a sine wave.     

LCD backlights: with or without Hg?

High luminance and efficacy vs. temperature independence and environmental protection: these are the determining factors for the choice of Hg or Xe for LCD backlights. A capacity‐coupled cylindrical Hg discharge lamp attains a luminance of 114,000 cd/m² and an efficacy of 35 lm/W when driven at 5 MHz. On the other hand, a mercury‐free Xe flat discharge backlight produces 11,000 cd/m² and 30 lm/W, with fast luminance response. This paper discusses the underlying limitations assessed to the Hg and Xe backlights, considering application to LC TVs.     

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     

Higher‐output more‐compact UHP lamp systems

Abstract— Projection systems have reached convincing performance with several thousand screen lumens created by systems of only a few liters in volume. With more than 10 lm/W they are the most efficient display systems realized today. The tremendous progress achieved up to now relies on the outstanding properties of the UHP lamp. The combination of high brightness with lifetimes extending up to more than 10,000 hours is ideal for projection applications. This paper will summarize some recent technological achievements: the volume of the lamp and driver system has been reduced by a factor of 10, exploiting a reduced ignition voltage as well as new optical concepts for the reflector. The optical performance of short‐arc projection lamps can be improved dramatically: a dichroic coating on one half of the UHP burner is applied to focus all light into one hemisphere. This allows for extremely compact reflector systems and an improvement by 20–30% in light collection.     

Electro‐optical characteristics of a radio‐frequency plasma‐display module

Abstract— Plasma‐display modules intended for piled screens driven by a radio‐frequency voltage were investigated. The frequency range of a high‐efficiency RF discharge was determined. An efficiency of 4 lm/W at a brightness of 5000 cd/m² was obtained.     

High‐efficacy drive of spatial positive‐column‐discharge PDP with delayed D pulses

Abstract— A thick‐film ceramic‐sheet PDP provides a long sustain discharge gap of 0.45 mm, enabling the use of positive column discharges. The discharges are established in the middle of the discharge space and are completely free from touching the surface of substrates. This allows for the reduction in diffusion losses of the charged particles. To further improve the efficacy, delayed D pulses are applied to the address electrodes during the sustain period. Although the pulses only draw a little current, they perturb the electric field, reducing the peak discharge current and hence resulting in higher efficacy and luminance. The efficacy and luminance increase by 35% and 38%, respectively, with the delayed D pulses. These pulses are incorporated into the contiguous‐subfield erase‐addressing drive scheme for TV application. A short gap of 70 μm between the sustain and data electrodes generates a fast‐rising discharge and allows a high‐speed addressing of 0.25 μsec. This provides 18 contiguous subfields for the full‐HD single‐scan mode, with 70% light emission duty. A luminous efficacy of 6.0 lm/W can been attained using Ne + 30% Xe 47 kPa, a sustain voltage of 320 V, and a sustain frequency of 3.3 kHz, when the luminance is 157 cd/m². Alternatively, the panel can achieve 4.2 lm/W and 1260 cd/m² by increasing the sustain frequency to 33 kHz.     

High‐luminance and luminous‐efficacy mercury‐free flat fluorescent lamp (MFFL) with local‐dimming functionality

Abstract— In order to realize high‐luminance and luminous‐efficacy mercury‐free flat fluorescent lamps (MFFLs) for LCD backlighting, the phosphor profile was optimized to enlarge the surface area. The proposed uneven profile of the rear phosphor increases the effective surface area of the phosphor, resulting in a wide luminance range from 3000 to 16,788 cd/m² with a corresponding high luminous efficacy from 66 to 34.7 lm/W, respectively. Also, a dynamic operation method for an adaptive local‐dimming and scanning operation is proposed which can be used in a 32‐in. multi‐structured configuration having one inverter system. With the deployment of the bipolar drive scheme and dual auxiliary electrodes, a stable and selective diffuse glow discharge with high luminance is possible.     

Technology trends of high‐pressure mercury short‐arc lamps for projection systems

Abstract— We will discuss the advantages and limitations of ac and dc lamp technology for microdisplay‐based projection systems. The performance of the lamp in terms of brilliance and thermal robustness together with the potential lamp lifetime for ac and dc lamps will be discussed. ac and dc lamp designs will be evaluated to judge their potential for future improvements in terms of usable projector lumens.     

Dual‐feed full‐metal‐case antenna for WWAN/LTE smartphone applications

A dual‐feed small size full‐metal‐case (FMC) antenna for hepta‐band LTE/WWAN operation in smartphone applications is presented. The antenna proposed here is an integrated part of the full metal case located at the top edge of the smartphone, and it only occupies a small volume of 5 mm × 70 mm × 6 mm. It has two feeding ports that are separately connected to an ON/OFF switch (SW1 and SW2) for controlling the lower and higher operation bands, respectively. For the case when SW1 (ON) and SW2 (OFF), Port‐1 is engaged, and a lower operating band that covers the GSM850/900 operation (824–960 MHz) is achieved. In contrast, Port‐2 will be engaged for the case when SW1 (OFF) and SW2 (ON), and with the aid of a wideband matching circuit, the antenna can induce a higher operating band that can cover the DCS/PCS/UMTS2100/LTE2300/LTE2500 operations (1690–2690 MHz). Detailed design considerations of the proposed FMC antenna are described, and both experimental and simulation results are also presented and discussed. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:595–601, 2016.     

Practical CNT‐FED structure for high‐luminance character displays

Abstract— A high‐luminance CNT‐FED character display using a simple line rib structure was constructed. The display panel had 48 × 480 dots and the subpixel pitch was 1 mm. The greatest benefit of a display using CNT technology is high luminance performance with low‐power consumption. The luminance of the green‐color dot wasca. 10,000 cd/m² under 1/1 6 duty‐cycle driving at a 6‐kV anode voltage. The high luminance of the display panel can provide good visibility when installed even in outdoor locations, and the power consumption was ca. 4 W at the character displaying module. This, a CNT‐FED for character displays also has potential multifunctionality, which could be battery driven. It should be useful for public displays even under emergency no‐power conditions. In this work, a practical structure and process technologies for making ribs with reasonable cost were developed. The newly introduced 2‐mm‐tall line ribs as spacers were formed by using innovative production processes; i.e., the rib paste was pushed out of a multi‐slit nozzle, and the rib shape was formed by UV‐light irradiation. The developed panel structure and manufacturing processes also had the advantages of size flexibility and high production yield.     

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.     

High‐luminance and highly luminous‐efficient AC‐PDP with DelTA cell structure

To improve PDP performance, we developed an AC‐PDP with the Delta Tri‐Color Arrangement (DelTA) cell structure and arc‐shaped electrodes. The experimental panel has a pixel pitch of 1.08 mm and luminous efficacy of 3 lm/W at a luminance of 200 cd/m² despite its conventional gas mixture of Ne and Xe (4%) and conventional phosphor set. Moreover, its peak luminance can be greater than 1000 cd/m². The strong dependence of luminous efficacy on the sustain voltage is also discussed in this paper.     

Electron‐beam deposition of MgO on plastic substrate and manufacturing flexible flat fluorescent lamp

Abstract— A flexible fluorescent lamp that utilizes the same plasma discharge mode as in PDPs has been manufactured. The structure of the flexible lamp is simple and easy to manufacture. All‐plastic materials including plastic substrates, barrier ribs (spacers), and sealants for low‐temperature manufacturing processing have been adopted except for the phosphor and MgO thin film. The MgO thin films were coated on the plastic substrates as a protection layer against the plasma discharge. The adhesion and biaxial texture of MgO thin film deposited on the plastic substrates, poly‐ethyle‐nenaphthalate (PEN) and polycarbonate (PC), at low temperature (100–180°C) has been characterized. The MgO film on PEN shows good adhesion under a repeated bending test. The manufactured flexible lamp consists of two plastic substrates of about 3 in. on the diagonal, barrier rib (spacer), and external ITO electrodes. The Ne‐Xe (5%) gas mixture at 100–200 Torr was used for the discharge gas. A maximum surface luminance of about 100 cd/m² was achieved for a 1 ‐kHz AC pulse.     

A current‐mode tunable low‐supply‐voltage ring oscillator

A new circuit topology using a current‐mode low‐pass filter for sinusoids has been presented. The technique is relatively simple, in the proposed circuit, only three identical current‐mode low‐pass filters are connected to each other to realize the small signal path. No external passive components are required except for three capacitors. When compared with LC oscillators, the die area of this work, without inductors, is much smaller. When compared with voltage‐mode ring oscillators, the supply voltage of this work is much lower. As a particular example, a 2.4 GHz, 1.2‐V power supply, 5‐mW sinusoidal oscillator is demonstrated. The oscillation frequency is tuned by the value of that three capacitors, over ～900 MHz, and the tuning range is 37.5%. The phase noise results in ?94 and ?120 dBc/Hz at 1 and 10 MHz from the carrier, respectively. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Simulation of a high-power LED lamp for the evaluation and design of heat dissipation mechanisms

High-power LED lamps have been under intense development in recent years. However, issues related to heat dissipation on the LED chip continue to plague research efforts. Heat generation increases with the power of the LED chip and heat accumulation is exacerbated by the plastic casinge of the lamp. Accumulated heat can seriously shorten the lifespan of an LED device. Consequently, manufacturers are constantly seeking ways to improve heat dissipation via heat transfer mechanisms. Little analysis has been performed on coupling the fluid field and heat dissipation inside LED lamps. Using FLUENT software, this study developed a simulation method for LED lamps in order to investigate thermal and fluid fields inside a lamp. The simulation results of an 8 W LED lamp predicted a chip temperature of 75.1 °C and maximum air velocity of 97.3 mm/s within the lamp with two sets of air circulation. The proposed model facilitates new fin designs and the determination of the optimal inner-shell thickness with the proposed design of a LED lamp having 36 fins and an inner-shell thickness of 1 mm for increased heat dissipation.     

High‐performance white OLEDs with high color‐rendering index for next‐generation solid‐state lighting

Abstract— Several white‐OLED structures with a high color‐rendering index (CRI) were investigated for lighting applications. A two‐unit fluorescent/phosphorescent hybrid white OLED achieved an excellent CRI of 95, high luminous efficacy of 37 lm/W, and long lifetime of over 40,000 hours at 1000 cd/m². White‐OLED lighting panels of 8 × 8 cm for high‐luminance operation were fabricated, and a stable emission at 3000 cd/m² was confirmed. Quite a small variation in chromaticity in a different directions was achieved by using an optimized optical device structure. With a light‐outcoupling substrate, a higher efficacy of 56 lm/W, high CRI of 91, and longer half‐decay lifetime of over 150,000 hours at 1000 cd/m² was achieved. All‐phosphorescent white OLEDs placed on the light‐outcoupling substrate show a high CRI of 85 and higher efficacy of 65 lm/W with a fairly good half‐decay lifetime of over 30,000 hours. With a further voltage reduction and a high‐index spherical extractor, 128 lm/W at 1000 cd/m² has been achieved.     

Design and in‐vivo testing of a low‐cost miniaturized capsule system for body temperature monitoring

This article presents a stacked dipole antenna operating at industrial, scientific, and medical ‐ band (902‐928 MHz) for ingestible temperature monitoring applications. To date, the proposed capsule system has a smaller dimension of 11 mm (diameter) × 16 mm (length) compared to other existing capsule systems. To achieve size reduction of the capsule system, the conjugating matching method is utilized and the matching circuits are intended to be removed. The whole capsule system is simulated in a one‐layer muscle phantom for initial parameters optimization, and the impedance bandwidth ranges from 908 to 924 MHz, which is sufficient for data transmission requirements and also brings robustness on the performance stability whatever the surrounding organs is. A wireless data transfer link is established between the integrated capsule and external receiver. An in‐vivo measurement is also conducted to validate the system practicability, and besides, the temperature date of a rat is monitored in real time and shown at a display screen.