We have developed 10-inch RGBW LCD with edge-lit 2D local dimming backlight system for automotive applications. This prototype system has power consumption reduction performance of 41.5% compared to a conventional RGB display without local dimming backlight. The performance and evaluation results are described in this paper.
Author KeywordsAutomotive display, RGBW, Local Dimming, LCD, Backlight, Edge-lit, CIE2000
BackgroundThe backlights for automotive displays require high power consumption to obtain high luminance more than 1,000 cd/m2. High-resolution displays, as well as the current mobile displays are expected to be used for automotive in the near future, resulting in increased power consumption. Furthermore, there has been concern about the cost of the heat sink systems to suppress the increase in the temperature of automotive displays. As such, the development of displays with reduced power consumption is becoming increasingly important. Moreover, high-contrast characteristics, especially deep black, are required to achieve unity of interior design. We previously reported the development of an RGBW mobile display with a local dimming system [1] based on the "Extended HSV" color space model [2, 3] to reduce power consumption and obtain a higher contrast ratio. In our previous study [1], LEDs were placed on one side of the LCD module. To obtain over 1,000 cd/m2 luminance for high-resolution automotive displays, LEDs are placed on both sides of the LCD module in this study. Furthermore, a 2D local dimming system can be adapted to suppress increased backlight power consumption, which can achieved by optimizing the previous 1D local dimming algorithm for 2D.
Method for Determining LED PWM in 2D
We have developed a prototype of a head‐up display system using transmissive LCD with direct‐lit backlight type 2D local dimming and RGBW technology. We confirmed that the postcard effect, which is a phenomenon where the entire projection area including the noninformation area is slightly illuminated, was virtually eliminated. We also achieved higher white luminance and lower backlightpower.
We have developed an error-diffusion dithering method for a reflective MIP LCD to provide a high-quality moving image. We have restricted error diffusing area within several segments defined on the image without deterioration of the image quality, and successfully resolved the fluttering problem in moving image.
We have developed four primary‐color reflective LCD and have improved yellow and red color saturation. The color gamut area of the developed LCD meets to the standard for printing (SNAP) which is defined for reproduction quality in newsprint production. The developed LCD has also a wide color gamut, wide operating‐temperature range and high‐quality moving images. It is suitable to realize future digital signage for outdoors.
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