LCD减少背光如何保持亮度--加拿大Paper代写范文

加拿大Paper代写范文:“LCD减少背光如何保持亮度”，这篇论文主要描述的是目前市场上对于液晶显示器降低功耗的主要手段就是背光调光，然后提高显示器的图像处理，能够减少来自背光调光的影响，目前LCD的制造中提出了降低功耗让背光变暗，然后再通过增亮图像数据传送对BL进行调光，这样就能够通过图像缩放来补偿调光的系数，从而保证了在LCD背光减少的前提下，还能够帮吃LCD的亮度。

Backlight dimming is the predominant method for power reduction in LCD displays and image processing can compensate for such dimming. We propose a low complexity approach which replaces hard clipping with smooth roll-off.  A high quality approach preserves highlight detail.  Image quality is improved and power savings can be increases by more aggressive BL dimming capable with these methods.

Keywords: Low Power, LCD, brightness compensation

Introduction

The backlight is a significant source of power consumption in an LCD. In an effort to reduce power consumption an LCD can dim its backlight. Image dimming is an immediate consequence but can be compensated for by brightening the image data sent to the LCD. Since an LCD is a multiplicative system, dimming the BL can be compensated by scaling the LCD image by the inverse of the dimming factor. Several authors have proposed techniques which adapt the backlight to the brightness of the image and then use image processing to compensate for the BL reduction.  For typical content significant power savings have been reported based on this image adaptive back light scaling technique.  An important aspect of these works is selecting an appropriate BL level. 

The problem we address differs in that a fixed BL reduction is used and applied for all image content. The goal is to maintain high image quality with a fixed backlight reduction.  We examine the problem of preserving image quality when the desired image brightness exceeds the maximum brightness of the lower power display.  This can arise either due to system issues i.e. the ability to adapt the BL is unavailable or as part of an adaptive BL system with a more aggressive BL reduction strategy.  An important goal of our problem is preserving highlight detail when simple image scaling would result in clipping image data when compensating for BL dimming. We have developed two approaches to preserving image highlight detail while compensating for BL dimming.  Our goal is preserving image quality on a range of input imagery with a fixed backlight reduction in the range of 20%.

We provide a brief discussion of the ability to emulate full BL output on a reduced BL display.  The output of an sRGB calibrated LCD with two different BL levels is illustrated in Figure 1.  For a moderate output, as indicated by the dashed horizontal line, the low power display is capable of producing the same output luminance as the full power display if it is driven with different data.  Thus the backlight dimming can be compensated by image processing.

Figure 1 Photometric Matching

Compensation consists of multiplying the original data by the reciprocal of the relative illumination in the linear light domain before sending it to the low power display.  Analysis in Equation 1 shows this is equivalent to linear scaling in the digital code value domain by a factor dependant upon the relative power ratio and display gamma.

Compensation for BL dimming consists of a tone scale operator which is linear with a slope determined by the display gamma and the relative BL illumination.  Digital range limits on the tone scale generally impose some degree of clipping in the compensating tone scale.

Equation 1 BL compensation in Code Value Domain

Clipping arises when CV Reduced exceeds the code value range (e.g. 255).  

Previous work devoted to adaptive BL modulation has recognized this fact and selected an image dependant BL level which either avoids or minimizes the presence of clipping.  We do not have the luxury of increasing the BL for bright images and hence we consider other solutions to avoiding clipping artifacts.

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