Volume 20 Number 2, December 1996.

CONTENTS

New Lighting Installations in JapanSpecial Issue "The 7th International Symposium on the Science & Technology of Light Sources"

ABSTRACT

Thermionic Emission Characteristics on Current-Controlled Preheating of Fluorescent Lamp Cathodes

Minoru MYOJO and Ikuhiro OKUNO
Light Development Center Matsushita Electronics Corporation

This paper proposes a method for measuring the emission time under an optimum condition of current-controlled preheating of fluorescent lamp cathodes. Using this method, a thermionic emission curve equation for practical lamp cathodes has been newly arrived at and the relationship between supplied energy for cathodes and its emission curve has been clarified. In addition, it has become clear that the supplied energy, till the emission time is reached, has a minimum value which varies with time and the average cathode resistance changes with a short emission time. These indicate the necessity of some improvements on the present IEC standard for the preheating condition of fluorescent lamp cathodes.

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Multiplet Structure Calculations for Rare Earth Ions

Shinichi ITOH, Naoyoshi NAMEDA and Riichiro SAITO
Department of Information and Computer Science, University of Kagoshima
Department of Electronics Engineering, University of Electro-Communications

We obtain the multiplet energies for several rare earth (RE) ions by ab initio molecular orbital calculations including the spin-orbit interaction working on 4f electrons of RE. Because of a limitation of the ability of computations, the lower lying multiplet energies for Ce ³⁺, Nd³⁺, Eu³⁺, Gd³⁺ and Er³⁺ ions were calculated in this report. For the excitations of 4f electrons, the spin multiplicity in the multiplet terms for 4f ⁿ electrons does not hold (not always ? S=0) both in initial and final states by mixing different S states upon spin-orbit interaction. We estimated the possibility of the transitions for the multiplet terms for RE ions with use of the obtained electronic spin states of the 4f electrons.

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A Flat Fluorescent Lamp with Xe Dielectric Barrier Discharges

Takahiro URAKABE, Shigeki HARADA, Takeo SAIKATSU and Masao KARINO
Advanced Technology R&D Center, Mitsubishi Electric Corporation

This paper shows a new type of flat fluorescent lamps for LCD backlighting, which utilizes xenon dielectric barrier discharges. The lamp is made of two glass plates. The structure is very simple. It has advantages which are ascribed to the structure. It has good luminous characteristics in every lamp size, because the discharge gap is kept at a certain value irrespective of size. Due to the absence of mercury, it operates well at low temperatures. And the authors found that it was characterized with excellent luminance uniformity and good luminance maintenance. Moreover, the authors obtained a high luminous efficacy (27lm/W), by virtue of operating by a pulse wave of voltage. It was found that the efficacy was improved with decreasing the power per cycle, and in the case of the pulse wave, the lamp could be operated below the power of the sine wave operation.

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Experimental Study on the Behavior of a Fluorescent Lamp with Dimmer Control

Guan-Chyun Hsieh
Department of Electronic Engineering National Taiwan Institute of Technology, Taipei, Taiwan R. O. C.

Ping-Shen Sung
Taiwan Electric Research & Testing Center, Inc., Taipei, Taiwan R. O. C.

Eel-Peeng Tsai
China Electric Mfg. Corp., Taipei, Taiwan R. O. C.

This paper presents an experimental study on the behavior of a fluorescent lamp. The modelings of the fluorescent lamp before and after firing are proposed. The fluorescent lamp characterizes its behavior as an impedance especially in the high frequency. It can be modeled as a series combination of resistance and capacitance after firing. Both two elements are function of the lamp current, the operating frequency, and the lamp voltage. A half-bridge series-resonant parallel-loaded inverter (HB-SRI) is proposed for measuring the characteristic of the fluorescent lamp. Interestingly, the resonant frequency of the HB-SRI is dependent on the mentioned three variables. A design example of the HB-SRI inverter is presented for dimming a 40-Watt fluorescent lamp. The dimmer strategy to dim the fluorescent lamp is realized by varying the operation frequency or the power factor correction (PFC) output voltage. Three dimming sections are examined, and the proposed ballast provides a power factor up 0.997, lower temperature rise of below 27 °C , near 8 watts of power saving, and 10% increase of luminous efficacy.

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Influence of the Duty Cycle on the Time Behaviour of the VUV-Radiation and Densities of Excited Atoms in the Medium Pressure Xenon Discharge

Eckhard KINDEL and Conrad SCHIMKE
Institut fur Niedertemperatur-Plasmaphysik e.V. Robert-Blum-Str. 8-10, 17489 Greifswald GERMANY

A comparision between the dc and the pulsed medium pressure discharge in Xenon (10...100 Torr) has shown that a significantly higher VUV-radiation (140 to 180 nm) occurs in the pulsed discharge (rectangular pulses in the frequency range of some kHz). For a pulse repetition frequency of 6 kHz and a pulse current of 250 mA measurements of the VUV-radiation and the density of excited atoms (1s ₅, 1s₄) in dependence on the duty cycle are presented. It is shown, that the mean value of the VUV-radiation reaches a maximum in dependence on the duty cycle. The enhanced radiation in the pulsed mode is connected with the effect of dissociative recombination and the formation of excimer states.

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Built-in Starter with Pulse Cut-out for HID Lamps

Shunichi SASAK*, Takenobu IIDA** and Russell LOANE*** : Iwasaki Electric Co.,Ltd. Saitama Plant
** : Eye Lighting Industries Pty Limited

Recently, High Pressure Sodium lamps (H. P. S. L.) and Metal Halide lamps (M. H. L.) have been operated on Mercury vapour lamp ballasts. But for both H.P.S.L. and M.H.L. it is necessary to use a starter to ignite the lamp. The usual starter can create some problems being radio frequency noise generation, insulation failure and others caused by continuous pulsing at the point of lamp failure. One of the solutions to the above problems is to cut out the starting pulse when the lamp fails. This paper shows a new built-in starter for such lamps that can cut out the starting pulse when the lamp fails. This new built-in starter is constructed by a Ferro-Electric Capacitor (FEC) ^1,2) which has non-linearity characteristics, a semi-conductor switching device (SIDAC) and some resistors. This starter can generate the starting pulse using the FEC's non-linearity characteristics and also can cut out the pulse by means of losing its characteristics above Curie point. And for H.P.S. lamps, in the case of arc tube leakage into the vacuum outer jacket, an arcing will be formed on the FEC's surface by the starting pulse. Then the FEC will be fired, and the pulse will be cut out permanently.

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Short Arc Metal Halide Lamp with New Ingredients for LCD Projector

Nobuyoshi TAKEUCHI* ,Hideaki OMURA**, Masayuki WAKAMIYA*,Munehiro TABATA** and Yoshiki KITAHARA*
* : Light development Center, Matsushita Electronics Corp.
** : Device Engineering Development Center, Matsushita Electric Industrial Co., LTD.

A new metal halide lamp employing gadolinium-lutetium iodide additives for LCD projector usage has been developed. Emission from gadolinium-lutetium iodides contributed to a significant improvement of various color characteristics. The new additives also led to a longer lifetime of the lamp. Besides, the designing of a reinforced arc tube has been realized through the fracture behavior analysis, providing a highly reliable arc tube.

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Simplified Digital Still Image Compression Using Histograms of Wavelet Expansion Coefficients and Subjective Fidelity Estimation Between Similar Reconstructed Images

M. IIZUKA, M. KITAMURA and Y.NAKASHIMA*
Tokyo Institute of Polytechnics, Faculty of Engineering
* Toyama University, Faculty of Engineering

A part of this paper was presented using another original image of 128 X128 pixels with 16 gray levels at the Color Forum Japan '96 in Chiba 1996, September and at the 11th Digital Signal Symposium in Tottori 1996, November.

The main aim of wavelet transforms is to provide an intuitive and visual representation of digital signals or image data from the view-point of time-frequency or space-scale relation, respectively. A united square matrix for the two dimensional discrete wavelet transform (2D-DWT) is composed of a recurrent combination of spatial low-pass and high-pass filter coefficients, i.e., Daubechies filter coefficients for the scaling function and wavelet. A pair of forward and inverse DWT may be recursively performed by the united square matrix and orthogonal matrix operation techniques. In this paper, simplified digital still image compression techniques are discussed together with the histograms of wavelet expansion coefficients at the specified resolution level. The display results of a difference image : original image-reconstructed image in monochrome and quasi-color compared with a measure of the image fidelity such as RMSE and/or PSNR from the viewpoint of a subjective appearance of reconstructed images.

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