Power Reduction of OLED Displays by Tone Mapping Based on Helmholtz-Kohlrausch Effect

Tomokazu SHIGA  Soshi KITAHARA  

IEICE TRANSACTIONS on Electronics   Vol.E100-C   No.11   pp.1026-1030
Publication Date: 2017/11/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E100.C.1026
Type of Manuscript: Special Section PAPER (Special Section on Electronic Displays)
mobile display,  power reduction,  visual characteristic,  

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The Helmholtz-Kohlraush effect is a visual characteristic that humans perceive color having higher saturation as brighter. In the proposed method, the pixel value is reduced by increasing the saturation while maintaining the hue and value of HSV color space, resulting in power saving of OLED displays since the power consumption of OLED displays directly depends on the pixel value. Although the luminance decreases, brightness of image is maintained by the Helmholtz-Kohlraush effect. In order to suppress excessive increase of saturation, the increase factor of saturation is reduced with an increase in brightness. As maximum increase factor of saturation, kMAX, increases, more power is reduced but unpleasant color change takes place. From the subjective evaluation experiment with the 23 test images consisting of skin, natural and non-natural images, it is found that kMAX is less than 2.0 to suppress the unpleasant color change. When kMAX is 2.0, the power saving is 8.0%. The effectiveness of the proposed technique is confirmed by using a smart phone having 4.5 inches diagonal RGB AMOLED display.