为了研究环境亮度、背景色度变化以及干扰(镜面反射、漫反射和眩光)对平视显示器可读性的影响,通过对最小可辨差异(PJND)理论的研究，结合平视显示器及应用环境特点，建立了基于PJND的平视显示器可读性评价模型。仿真及实验结果表明: 可用PJND值来评价平视显示器的可读性；为满足可读性，随着环境亮度变大，亮度对比度应该逐渐减小，低亮度环境下对亮度对比度的要求大于高亮度环境；背景色度与目标色度差异越大，可读性对亮度对比度的要求越低；环境亮度不变、干扰值变大时，可通过增大亮度对比度来满足可读性，干扰值超过一定范围，可通过物理遮挡来满足可读性。

To study the impacts of environment luminance, chromaticity of background and interferences (including specular reflection, diffuse reflection and glare) on the readability of Head-Up Display (HUD), a readability evaluation model was established based on Perceptible Just Noticeable Difference (PJND) theory by taking the characteristics of HUD and its environment into consideration.Simulations and experiments result shows that:1) The value of PJND can be used for evaluating the readability of HUD;2) Low-luminance environment has a higher luminance contrast requirement than high-luminance environment;To satisfy the readability, the HUD needs to lower the luminance contrast when the ambient luminance increases;3) The bigger the difference between background chromaticity and object chromaticity, the lower the requirement to luminance contrast;and 4)When the environment luminance is constant and the interferences increase, a higher luminance contrast can be used to satisfy the readability;when the interference luminance is beyond the maximum, physical occlusion is a way to satisfy the readability.