Head-up displays (HUDs) can provide important driving information such as speed and navigation directly to a driver within their immediate field of view. Specifically, a dual-plane AR-HUD can provide drivers with larger images with richer information, more intuitive information presentation, and enhanced navigation features. To ensure driver comfort, proper presentation format of the text on the dual-plane HUD needs to be investigated. A human factors experiment was conducted to explore proper luminance contrast and font size of the text on a HUD. Twenty older and nine mid-age drivers were instructed to recognize letters in 14 levels of font size under each of eight levels of luminance contrast (ranging from 1.2:1, to 8:1) on each plane. The best test performance was observed at a luminance contrast of 7:1. We report the minimum and upper bound of 95% confidence interval of legible vertical visual angle for 99.5% of older drivers at each luminance contrast level. Although the typical legibility rule of thumb for font height versus distance on standard displays is 0.007 (known as the Bond rule), our experiment suggests that double that size (0.014) was needed to cover 99.5% of older drivers at a contrast ratio of 1.2:1 on a HUD.

中文翻译：

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亮度对比度和字体大小对双平面平视显示器清晰度的影响（“ HUD的Double 007规则”）

平视显示器（HUD）可以在其直接视野内直接向驾驶员提供重要的驾驶信息，例如速度和导航。具体来说，双平面AR-HUD可以为驾驶员提供更大的图像，其中包含更丰富的信息，更直观的信息表示以及增强的导航功能。为了确保驾驶员舒适，需要研究双平面HUD上文本的正确显示格式。进行了人为因素实验，以探索HUD上文本的适当亮度对比度和字体大小。指示二十名年龄较大的驾驶员和九名中年驾驶员在每个平面上的八个亮度对比度级别（从1.2：1到8：1）中的每个级别下，以14个字体大小的级别识别字母。在7：1的亮度对比下观察到最佳的测试性能。我们报告了99.5％的老年驾驶员在每个亮度对比度水平下，清晰的垂直视角95％置信区间的最小和上限。尽管标准显示器上字体高度与距离的典型易读性规则为0.007（称为Bond规则），但我们的实验表明，在对比度为1.2的情况下，要覆盖99.5％的老年驾驶员，则需要两倍的大小（0.014）。在HUD上为：1。