BRUCE: a metrological system for characterizing the beam-intensity rotational uniformity of side-scanning optical miniature probes.

To successfully translate optical miniature probes, such as the endoscopic miniprobe, catheter probe, and capsular probe, into clinical practice, it is essential to accurately characterize their performance and thereby precisely define the final specifications of the related device outcomes in various aspects such as biochemical, electrical, physical, mechanical, and optical aspects. Although a variety of related device concepts have been introduced in the biophotonics field in the past three decades, all the previous studies, to the best of our knowledge, focused on showcasing their biomedical potential or applications rather than developing or solidifying related metrologies to objectively characterize their performances. In this study, we developed a metrological system that can measure the beam-intensity rotational uniformity of a side-scanning optical miniature probe, regardless of its beam firing angle to the probe axis. Moreover, by applying the developed system to our photoacoustic endoscopic probe prior to conducting in vivo imaging experiments, we were able to confirm the beam uniformity far more accurately than was previously possible by visual inspection. In this paper, we introduce the basic concept and operating principles of the developed system and discuss the importance of characterizing the relevant beam-intensity uniformity.