Accurate calibration is crucial for using multiple cameras to triangulate the position of objects precisely. However, it is also a time-consuming process that needs to be repeated for every displacement of the cameras. The standard approach is to use a printed pattern with known geometry to estimate the intrinsic and extrinsic parameters of the cameras. The same idea can be applied to event-based cameras, though it requires extra work. By using frame reconstruction from events, a printed pattern can be detected. A blinking pattern can also be displayed on a screen. Then, the pattern can be directly detected from the events. Such calibration methods can provide accurate intrinsic calibration for both frame- and event-based cameras. However, using 2D patterns has several limitations for multi-camera extrinsic calibration, with cameras possessing highly different points of view and a wide baseline. The 2D pattern can only be detected from one direction and needs to be of significant size to compensate for its distance to the camera. This makes the extrinsic calibration time-consuming and cumbersome. To overcome these limitations, we propose eWand, a new method that uses blinking LEDs inside opaque spheres instead of a printed or displayed pattern. Our method provides a faster, easier-to-use extrinsic calibration approach that maintains high accuracy for both event- and frame-based cameras.

翻译：精确标定对于使用多个相机精确三角测量物体位置至关重要，但这也是一个耗时的过程，每次相机移动后都需要重复进行。标准方法是使用已知几何形状的打印图案来估计相机的内参和外参。同样的思路可应用于事件基相机，但需要额外工作：通过从事件中重建帧，可检测打印图案；或在屏幕上显示闪烁图案，直接从事件中检测该图案。此类标定方法可为帧基和事件基相机提供精确的内参标定。然而，对于具有差异极大的视角和宽基线的多相机外参标定，使用二维图案存在若干局限：二维图案仅能从单一方向检测，且需足够大的尺寸以补偿其与相机的距离。这导致外参标定耗时且繁琐。为克服这些局限，我们提出eWand——一种使用不透明球体内闪烁LED灯而非打印或显示图案的新方法。该方法提供了一种更快、更易用的外参标定方案，且能同时为事件基和帧基相机保持高精度。