Color models and color processing for LCDs with RGB-LED backlight and/or quadruple color filter


Objective: For newer LCD display types, RGB-LEDs may be the light source allowing a colorful backlight. The color filters may consist of more than the RGB filter, for example RGBW or RGBY. The interaction between the backlight and the color filter will be modelled. Based on these specific models for the new LCD types, the RGB image data will be rendered for variable backlight and the quadruple subpixels. Through these color models and color processing, the power efficiency as well as the display brightness is to be increased. Also the color gamut may be extended. It is the base for a combination with 2D (gray) local dimming technology, also called as 3D (color) local dimming, which should increase the power efficiency additionally.

Digital drive of AMOLED


Objective: Instead of analog driving as with state of the art technology, the driving transistor of the pixel circuit is operated in switch mode. The variation and the drift of the TFT transistor parameters are no more an issue, so that high yield and simple process will be enabled. The voltage drop on the driving transistor is due to the switch mode very low, so that the power consumption of the AMOLED panel is reduced by 35%. The challenges are artifacts due to the non-uniform thermal distribution, trace resistance and so on. We work on method decomposing the image into binary subfarmes of which the generated light distribution are summed up to the image desired. 

Local Dimming of automotive displays implemented on FPGA


Objective: the automotive displays is a very demanding application for local dimming, while the advantages are also huge. Under sunlight, the display must be very bright so that beside the power consumption the heat dissipation is a serious problem requiring heavy and large heat sink. In the night operation, the ambient is dark so that the LCD panel appears rather grey. Such a grey appearance makes the interior design less convenient. Local dimming may drastically enhance the black level and make the interior deisgn much more classy. The major challenge is that the image is often of graphic content so that the uniformity requirement is high, especially for the night operation. Therefore few modes for diverse ambient conditions are to be considered. For the sunshine the power saving is the absolute priority, while compromise at image quality may be accepted. For the night operation, image quality like black level outperforms the power saving. For this purpose, the correlation between the image and the backlight distribution is a further metrics to be optimized. Since FPGA is chosen as the HW, the implementation may be easily modified. User tests and few iterations are planned to get the best trade-off for each mode. A user test is planned.

Local Dimming of tablet/notebook monitors based on GPU


Objective: the monitor consumes today 25% of the total power of a notebook. In the near future, this share will rise to 75%. The power saving feature of local dimming fits therefore ideally for increasing the battery operation time of a tablet/notebook and/or making the battery smaller, lighter and cheaper. Since a graphic processing unit is always available, a SW-based solution e.g. in Open CL, Cuda etc may be implemented without any HW-cost. We will work on an efficient and generic implementation which can quickly be adapted to a specific table/notebook model. The algorithm shall be able to run on a small GPU and allow high frame rate like 120 Hz. The visual reslts will be validated and demonstrated on a modified monitor with 16 LED strings. In addition, the processing of the image data will consider specific requirements derived from the diverse contents of mobile computing applications. The ambient light will also be considered.

Local Dimming of LED LCD TVs implemented on ASICs

Objective: The TV application consumes roughly 10% of electricity of private households. The power consumption will further increase, since the screen size, the display brightness and the number of TV sets will increase. In order to reduce/limit this power consumption, most governments of the world set regulation like energy label. This was the motivation of our research in the field of local dimming LCD backlight. Since TV is a high volume market, it is very cost-sensitive. The local dimming technology must therefore be a part of a System on a Chip for TV. There are three objectives: 1) high power saving; 2) high visual quality; 3) lower HW cost. High power saving may even improve the visual quality like static contrast. The clouding artifact, which is the most annoying disadvantage of the Edge-Lit/Side-Lit LCD, may disappear. However, high power saving rate may produce perceivable undesirable artifacts like clipping. The algorithm should suppress visible clipping and allow a better trade-off between power saving and clipping. In addition, the algorithm and the HW design must be higly efficient. This means that the logic complexity and the memory needed are low, while the processing speed is high allowing high frame rate. 

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