公路隧道进出口亮度的急剧变化会造成驾驶员视觉适应困难，严重时甚至导致交通事故。
The sharp variation of luminance at the entrance and exit of highway tunnel will cause the difficulty in visual adaptation of the driver, and even lead to traffic accidents.
目的评估3种背景环境下的中间视觉对比度阈值，并探讨暗适应时间、背景亮度和眩光对人眼对比度阈值的影响。
Object: to evaluate mesopic contrast threshold under 3 kinds of background and to explore the effect of adaptation time, adaptation luminance and glare on contrast threshold of humans eye.
分析人类视觉系统的亮度和对比度特性，提出了一种DCT域自适应可见水印算法。
By analyzing the characteristics of the brightness and contrast characteristic of the human visual system, an adaptive visible watermarking algorithm based on DCT was proposed in this paper.
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