Hue-shift Model for DLP Projector with the White Peaking Function

摘要

Projectors have become common display devices, not only for office and school presentations, but also for home theater entertainment. Although a completely dark room is the ideal venue for watching a projected image, in most situations (including classrooms and conference rooms) the viewing conditions are not completely dark, and ambient light falling on the screen produces a background light level with the image projected on top. As the background light increases, it becomes more difficult to see the projected image, which becomes dull and may appear washed out. What is really happening is that the ambient light reduces the contrast of the image. While the amount of light contributing to the image remains the same, more light has been projected onto the screen by other light sources. This effect can be reduced by employing the white-peaking function of a digital light-processing (DLP) projector, which adjusts the white segment of the color wheel, resulting in more natural and vivid images. Although the chromaticity coordinates for an image projected with and without white peaking are the same, when white is added to the projected image, the perceived hue changes. This phenomenon is known as the Abney effect. This paper presents a model of this hue-shift phenomenon and proposes a hue-correction method. For evaluation purposes, an observer-preference test is conducted on several test images with and without hue shifts, and z-scores are utilized to compare the results.