Optical Center Alignment for High-speed High-precision Laser Tracking

Summary

The technology for continuously projecting a laser beam onto a predetermined position on a moving target is expected to be in demand in various applications, such as free-space optical communication and laser processing/fabrication. Generally, tracking a three-dimensionally moving target and projecting a laser beam requires three-dimensional calibration of multiple cameras and a laser scanning system. However, if the optical center of the high-speed camera used for tracking coincides with the rotational center of the laser scanning system, tracking projection becomes possible using only two-dimensional recognition processing, eliminating the need for three-dimensional calibration. This facilitates wide-area laser tracking projection, but precisely aligning these optical centers by visual inspection or manual adjustment alone is difficult.

This study proposes an interactive high-precision calibration method (Fig. 1) for the optical centers between a galvanometer mirror laser scanning system and a high-speed camera, aimed at achieving high-speed, high-precision laser tracking. Using circular pattern projection onto screens containing slits at different depths, image processing visualizes the deviation of circular parameters on each screen (Fig. 2), enabling high-precision translational alignment. Experimentally, this enables sub-pixel calibration accuracy (Fig. 3) and high-speed, high-precision laser tracking projection (Fig. 4). Compared with a laser tracking (information display and VibroTracker) using a 1-ms auto pan–tilt technology developed in our laboratory, the proposed system enables laser tracking using relatively inexpensive and compact modules, while offering high scalability to multiple units. Industrial applications are anticipated, such as free-space optical communication and laser processing, where predicting the target motion is challenging.

This content is based on the results of joint research with NEC Corporation.

Fig. 1 Alignment system.	Fig. 2 Circle detection image processing.
Fig. 3 Alignment results.	Fig. 4 High-speed high-precision laser tracking.

Movie

Reference

1. Tomohiro Sueishi, Keiko Yokoyama, and Masatoshi Ishikawa: Calibration of Optical Center Alignment between a High-Speed Camera and Galvanometer Mirrors for High-Precision Laser Tracking, 2026 IEEE/SICE International Symposium on System Integration (SII2026) (Cancun, 2026.1.13)/Proceedings, pp. 645-650