A new local dimming algorithm based on the simplex method

Abstract

A recently arising important feature of mobile computing is power efficiency. Economical power management allows to increase the battery lifetime of tablets, mobile phones and so on. As the display of those devices yields the largest part of power consumption in the near future, it is necessary to reduce the power consumption of them. This can be achieved by dimming, especially by local dimming, i.e reducing the backlight of the display while the necessary brightness in all pixels has to be satisfied. Mathematically, this problem is modeled in this paper as a linear program, which will be solved by a tuned up version of the popular simplex algorithm. While there are other methods as the sorted sector covering algorithm or the General Dimming Algorithm for local dimming, they do not allow to integrate a-priori information for the solution. For example, restricting the maximum difference of the power of two neighboring LEDs is not possible due to the calculation, while it is a natural demand from the physical point of view. Furthermore, the simplex method allows to integrate smoothness conditions on the solution depending on the second order derivative. Additionally, a problem adapted pivot rule is proposed and the warmstart-strategy of the simplex is elaborated to speed up the proposed algorithm during watching movies. Furthermore, the new method does not only minimize the power consumption, it also aligns the backlight to the image leading to perfectly dimmed images. Numerical examples comparing the different methods substantiate the many advantages of the new method.