基于印刷字体的单目距离估计用于高级驾驶辅助系统
Calibrated Multichannel Monocular Ranging From Standardized License Plates With Metrology-Exact Validation
- University of Michigan-Dearborn（密歇根大学迪尔伯恩分校）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
提出利用后车牌字符高度等标准尺寸，通过单目相机检测车牌并测量字符高度、笔画宽度等，结合状态识别和相机投影，实现低成本、高精度的前车距离估计，误差小于0.13米。
AI中文摘要：
估计与前车的距离是前向碰撞预警、自适应巡航控制和自动紧急制动的基本输入。生产系统通过雷达、激光扫描仪或立体相机对获得该距离，这增加了成本、功耗和封装约束。本文探讨是否可以通过使用一个尺寸标准化且每辆道路车辆上都存在的目标——后车牌，用单个普通相机恢复相同的距离。美国车牌具有固定的外部尺寸和法规规定的字符高度，各州之间差异很小，因此一旦相机几何参数已知，图像中车牌字符的高度就是距离的直接度量。所提出的方法（基于印刷字体的单目距离估计）检测车牌，测量其印刷字符的高度，识别发牌州以选择正确的物理字符高度，并通过相机投影恢复距离。从同一车牌获取三个测量值：字符高度、笔画宽度和字符间距。结合两个安装孔的间距和单图像深度网络，自动对弱或损坏的测量值赋予较低权重。距离、其变化率和碰撞时间估计在帧间平滑，并用于按照美国碰撞预警法规的时序发出警告。固定尺度的车牌还标识了车辆，因此该方法从一个被动传感器返回距离、方位和身份。它从印刷标准而非飞行时间或视差读取尺度，使其成为容错感知栈中这些传感器的低成本、低维护补充，实现了误差小于0.13米的低成本距离估计。
英文摘要：
Longitudinal driver assistance depends on the distance to the vehicle ahead, a quantity normally supplied by radar, laser scanner, or stereo pair. However, a low-cost camera can estimate the distance as well, taking the rear license plate as a metric reference, including standards fix both the plate envelope and the regulated character height, so the pinhole projection converts either one into a distance. This research presents a approach and validates it. Plate localization now withstands the low-contrast and cluttered frames that previously drew the detector onto the vehicle body, or onto the character cluster of a sparsely lettered plate. Character height, plate outline, and mounting-hole span form three distance channels, merged by a consensus gated inverse-variance fusion that discards a corrupted channel before it can bias the result, with each channel separately corrected for the foreshortening of the direction along which it is measured, the correction following from the plate's recovered attitude. Finally, an innovation gate protects the temporal filter, so that a single bad detection cannot become a false warning. Evaluation is carried out in a metrology-exact testbed in which the commanded distance is the true distance, through 51 USA registries with distances of 1 to 12 m and viewing angles to 30 degrees under five lighting conditions. The plate is located in every frame. Mean absolute percentage error is 4.32% for the outline channel, while the fusion returns 5.79% mean and 2.17% median, without any of its single-channel failure modes. Roll is recovered to within one degree; the two out-of-plane tilts only to within several. The algorithm can provide a solid foundation for low-cost distance estimation which can serve as an emergency backup for other sensors.
