S. Mikoshiba

44.4: RGB-LED Backlights for LCD-TVs with 0D, 1D, and 2D Adaptive Dimming

Output luminance of an RGB-LED backlight for an LCD-TV was adaptively dimmed along with input video signal in fashions of 0D (uniform dimming), 1D (line dimming), and 2D (local dimming). It has been proven experimentally that the backlight power can be reduced to 83%, 71%, and 50%, respectively, for a typical sample movie having 8.0% post-gamma average picture level (which is equal to the average luminance level). Further simulation study revealed that the power consumption can be reduced to the value equal to that of the post-gamma APL.

Degradation of moving-image quality in PDPs : Dynamic false contours

When moving images are displayed on matrix displays which reproduce gray levels utilizing pulse-number/width-modulation techniques, degradation of the gray levels and colors are often observed. The degradation originates from a temporal non-uniformity of the light-emission pattern, which is transformed into a spatial non-uniformity of the light emission due to an after-image effect of the eyes, which follow the image motion. The degradation becomes appreciable when the product of the speed of the viewing point on a screen and the light-emission period of a pixel is greater than the pixel pitch. The degree of degradation is also affected by the pixel arrangement; disturbances for the stripe arrangement are worse than those for the triangle arrangement. The temporal uniformity is degraded when the major light-emitting blocks of the pulse-number/width-modulation change. The uniformity can be improved by dividing the blocks of the major bits. It was analytically verified that the perceived luminance of periodic light emission is proportional to the emission duty factor (which coincides with Talbot-Plateaus law) and also to the integral of f(t)dt from zero to infinity, independent of decay shape, f(t), of the after-image.

37.3: Mercury‐Free, Simple‐Stuctured Flat Discharge LCD Backlights Ranging from 0.5 to 5.2‐in. Diagonals

Mercury-free flat discharge lamps with diagonal sizes ranging from 5.0 to 5.2 inches have been developed for LCD backlights. The lamps have simple structures with insulated electrodes. Uniform discharges are obtained by adjusting drive pulse voltage and waveforms. As lamp diagonal becomes larger, luminance and efficacy increa-se, and the dimming can be varied in wider range.

Power savings and enhancement of gray-scale capability of LCD TVs with an adaptive dimming technique

Abstract— The luminance of a backlight unit for an LCD TV is adaptively and locally dimmed along with the input video signal in order to reduce the power consumption and also to improve the picture quality. By adopting the zero-dimensional (0D), 1D, and 2D adaptive dimming techniques, a sample movie having 8.0% post-gamma average picture levels (APL) could be displayed using 83%, 71%, and 50% of the original backlight power, respectively. For an adoption of the 2D dimming, an LED backlight is preferable. The adaptive-dimming technique also allows the differential aging characteristics between the LED components and temperature dependence of color and luminance to be overcome. From simulations of a reduction in power consumption, it was found that 40 × 40 pixels is a unit of the local dimming, 30 frames for the sampling period, 24 dimming steps, and an equal-signal-step method for determining the dimming factor have been found to be appropriate. The gray-scale capability of low-luminance images can also be improved by dimming the backlight luminance and expanding the input signal. By using an LCD TV having an 8-bit capability, an 11-bit-equivalent gray-scale expression was experimentally proven.

19.1: Invited Paper: Xe Discharge Backlights for LCDs

Mercury-free, Xe fluorescent lamps are becoming more and more important for LCD backlights, not only from the environmental point of view but for attaining high picture quality. The paper explains underlying limitations assessed to the Xe glow discharges and introduces various Xe backlights with a stress on a flat discharge lamp.

High-frequency drive of high-Xe-content PDPs for high efficiency and low-voltage performance

— It has been well known that the luminous efficiency of PDPs can be improved by increasing the Xe content in the panel. For instance, the efficiency is improved by a factor 1.7 when the Xe content is increased from 3.5% to 30%. The sustain pulse voltage, however, increases from 180 to 230 V by a factor 1.3. It was found that the increase in the sustain pulse voltage can be suppressed by increasing the sustain pulse frequency. The high-frequency operation further increases the luminous efficiency. If the Xe content is increased from 3.5% to 30% and the drive pulse frequency is increased from 147 to 313 kHz, the luminous efficiency becomes 2.7 times higher and the luminance 4.5 times higher. Furthermore, the increase in the sustain pulse voltage is suppressed 1.1 times, from 180 to 200 V. A mechanism of attaining high efficiency and low-voltage performance can be considered as follows. A train of pulses is applied during a sustain period. As the sustain pulse frequency is increased, the pulse repetition rate becomes faster and a percentage of the space charge created by the previous pulse remains until the following pulse is applied. Due to the priming effect of these space charge, the discharge current build-up becomes faster, the width of the discharge current becomes narrower, ion-heating loss is reduced, and the effective electron temperature is optimized so that Xe atoms are excited more efficiently. The intensity of Xe 147-nm radiation, dominant in low-pressure Xe dis-charges, saturates with respect to electron density due to plasma saturation. This determines the high end of the sustain pulse frequency.

26.1: Invited Paper: Visual Artifacts Generated in Frame-Sequential Display Devices: An Overview

Many display devices including color PDPs, DMDs, ferroelectric LCDs, and ELs express gray levels by accumulating pictures of multiple sub-frames with the aid of retinal after-image effect. Additionally, some of these devices use frame-sequential color-multiplexed backlights. When the observers eye sweeps across the screen, unexpected visual artifacts, e.g. false contours and color breakup may be produced. These artifacts will be quantified, and methods of reducing them will be introduced.

Secondary electron emission and glow discharge properties of 12CaO·7Al2O3 electride for fluorescent lamp applications

Abstract 12CaO·7Al2O3 electride, a sub-nanoporous compound having a work function of 2.4 eV, was examined as a candidate cathode material in fluorescent lamps. The electron emission yield was higher and the discharge voltage was lower for 12CaO·7Al2O3 than for existing cathode materials such as Ni, Mo or W; therefore, the energy consumption of the fluorescent lamps can be improved using 12CaO·7Al2O3 cathodes. Prototype glow-discharge lamps using 12CaO·7Al2O3 were constructed and exhibited reasonable durability.

43.2: Driving of PDPs with 208 Sub-Fields Using a Grouped Address-While-Display Scheme

Driving of AC-PDPs with as many as 208 sub-fields has been realized by using a grouped Address-While-Display (AWD) scheme, which combines the AWD and low-voltage-addressing techniques. The drive scheme provides high picture quality with a wide choice of gamma characteristics. Also, dynamic false contours can be eliminated.

30.2: A Gray Scale Expression Technique Having Constant Increments of Perceived Luminance Using a Contiguous Subfield Scheme

A technique is introduced with which increments of perceived luminance at each jump of the gray level can be made constant. This improves the gray scale expression at low luminance levels. The technique also allows to compensate for the phosphor/VUV saturation, and can provide any of the I/O characteristics to enhance image expression.