Tomokazu Shiga

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.

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.

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.

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.

Xe-excitation efficiency and plasma saturation in plasma display microdischarges

Plasma display panel (PDP) efficiency data are correlated with panel emission measurements. A large visible/infrared (vis/IR) ratio of the phosphor emission in the visible to the Xe emission in the infrared indicates a high Xe-excitation efficiency. Monitoring the changes in the vis/IR ratio allows a decomposition of the discharge efficiency into Xe-excitation efficiency and electron heating efficiency contributions. For several different PDP efficiency dependencies on sustain voltage and frequency, consistent trends in Xe-excitation efficiency and electron heating efficiency are found. In addition, in order to follow the discharge development, the time dependence and the spatial distribution of the Xe emission are monitored. The combined results show that plasma saturation is significant to low Xe-content panels in default operation conditions and that plasma saturation decreases with the high voltage high frequency operation of high Xe-content panels. These driving conditions, which are especially suited for high Xe-content panels, govern a fast and spatially distributed discharge development with a lower effective electron temperature, increased Xe-excitation efficiency, and decreased plasma saturation.

14.3: Distinguished Student Paper: A 121 Contiguous‐Subfield Addressing of High Xe Content PDPs

As the Xe content of PDPs is increased, space charge priming becomes more effective, resulting in faster and lower voltage addressing. A 30% Xe PDP was driven with 121 contiguous subfields using an erase addressing and a grouped AWD scheme. Crosstalks were suppressed by driving the odd and even sustain electrodes separately.

19.2: A 100,000-cd/m2, Capacity Coupled Electrodeless Discharge Backlight with High Efficacy for LC TVs

A capacity coupled electrodeless Hg discharge lamp has been developed for LC-TV backlightings. By applying sinusoidal voltages which are 180 degrees out of phase to a pair of external electrodes, luminous uniformity of over 84 % was attained in two types of lamps whose lengths are 190mm and 390mm. Luminance, efficacy, and input power to the lamp were 114,000cd/m2, 35 lm/W, and 21.5W when the 390mm lamp was driven at 5MHz with an inverter.

The 121-contiguous-subfield addressing of high Xe-content PDPs

— As the Xe content of PDPs is increased, the space-charge priming becomes more effective. Also, the diffusion/drift of the space charges and accumulation of the wall charges becomes faster. These facts indicate that the use of an erase addressing is preferable for high-Xe-content PDPs. A 30%-Xe green test panel was driven with contiguous subfields using erase addressing and a grouped Address-While-Display scheme. Crosstalk was suppressed by driving the odd and even sustain electrodes separately. The fast addressing speed of 0.283 μsec allowed for 121 subfields and 122 gray levels, with a resultant luminance of 4200 cd/m2 and a dark-room contrast of 310:1. The scan and data pulse voltages were as low as 90 and 75 V, respectively. All the subfields had an identical length of 136 μsec, but the number of sustain pulses in these subfields could be varied between 2 and 20. By selecting an adequate number of sustain pulses in the subfields, arbitrary gamma characteristics could be realized. A gray-scale expression having a constant difference between the consecutive “perceived” luminance levels was verified throughout all the luminance levels.