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Mobile displays such as personal digital assistants and cellular phones encounter various illumination levels, different from the flat panel displays mainly used in indoor environment. In particular, in the daylight condition, the displayed images or text on a mobile display can be darkly perceived, which results in the degradation of sun readability in a mobile display. To overcome this problem, we proposed an illumination level adaptive color reproduction method with a lightness adaptation model and flare compensation. Lightness adaptation is a physiological mechanism to shift the photoreceptor response curve according to the illumination level. Thus, as a mobile phone is carried from an indoor to outdoor environment, the photoreceptor response curve automatically shifts toward a higher luminance to adapt to daylight intensity. Consequently, for a lower intensity emitted from the mobile display, the photoreceptor response curve becomes less sensitive, thereby decreasing the perceived brightness of the displayed image. Moreover, colors produced by mobile display can also be influenced by the flare, defined as ambient light reflected from the display panel, which reduces the maximum chroma of the mobile display gamut. Based on these physiological and physical phenomena, the lightness values of the input image are enhanced by making a linear relation between input luminance value estimated by device characterization and photoreceptor response value calculated from the lightness adaptation model. For the chroma component of the lightness-enhanced input image, chroma compensation is conducted by adding the chroma values of the flare multiplied by the enhancement parameter, depending on the hue plane of the gamut boundary. Throughout the experiment, the proposed algorithm not only reproduces bright and colorful images in the mobile display under daylight conditions, but also produces a solution to improve sunlight readability.

We developed a high-quality plasma enhanced atomic layer deposited (PEALD) aluminum oxynitride (AlO x N y ) process for the metal-oxide-semiconductor (MOS) gate insulator of fully-recessed-gate AlGaN/GaN-on-Si MOS-heterojunction field-effect transistors (MOS-HFETs). It was found that the cyclic nitrogen incorporation into aluminum oxide (Al 2 O 3 ) during PEALD process improved the conduction band offset at GaN interface resulting in higher forward breakdown field strength, which also contributed to suppressed trapping effects under forward gate bias stress. Improved interface characteristics, which resulted from suppressed surface oxidation, led to significant improvement of threshold voltage stability. A low threshold voltage hysteresis of 180 mV at maximum gate sweep voltage of 10 V was obtained with AlO x N y gate insulator. The MOS channel mobility was also improved to 235 cm 2 V −1 s −1 . The fabricated fully-recessed-gate AlGaN/GaN-on-Si MOS-HFET with PEALD AlO x N y gate insulator exhibited excellent overall performances such as a threshold voltage of 3.2 V, a maximum drain current density of 481 mA mm −1 , an on/off current ratio of ∼10 10 , an ON-resistance of 12 mΩ mm, and a breakdown voltage of 1050 V.

This paper proposes an improved six-color separation method that reduces the graininess in middle tone regions based on the standard deviation of lightness and chrominance in SCIELAB space. Graininess is regarded as the visual perception of the fluctuation of the lightness of light cyan and cyan or light magenta and magenta. In conventional methods, granularity is extremely heuristic and inaccurate due to the use of a visual examination score. Accordingly, this paper proposes an objective method for calculating granularity for six-color separation. First, the lightness, redness-greenness, and yellowness-blueness of SCIELAB space is calculated, reflecting the spatial-color sensitivity of the human eye and the sum of the three standard deviations normalized. Finally, after assigning the proposed granularity to a lookup table, the objective granularity is applied to six-color separation , thereby reducing the graininess in middle tone regions.

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