Reduction of speckle effect using galvanometer scanners in a laser-based uniform source for radiance responsivity measurement

• Published in: Measurement : journal of the International Measurement Confederation 2025-01, Vol.242, p.115873, Article 115873
• Main Authors: Liu, Zhiwei, Zhao, Weiqiang, Gan, Haiyong, Zuo, Hongzhi, Liu, Wende, Liu, Xiangliang, Fan, Qiming, Lin, Yandong, Xu, Nan
• Format: Article
• Language: English
• ISSN: 0263-2241
• DOI: 10.1016/j.measurement.2024.115873

•Speckle effect affects detector-based radiance calibration accuracy.•Reduction of speckle effect using galvanometer scanners greatly improved source nonuniformity.•Speckle patterns superposition reduces the source nonuniformity through both simulation and experiments.•Using galvanometer scanners can improve power stability of the uniform source. Narrow linewidth lasers play an important role in high-spectral and high-precision radiometric calibration. In this paper, a standard uniform light source for radiometric calibration of imaging detectors and devices is designed and realized based on narrow linewidth laser and intergrating sphere. Because the speckle effect caused by laser has a great influence on the radiance transfer, galvanometer scanners were employed to reduce the speckle effect. CCD method was used to measure the nonuniformity of the middle row/column of the integrating sphere exit, and nonuniformity reduced from 2.6 % to 0.72 % when the galvanometer scanners were turned on. By superimposing 9 different regions of static speckle image, the non-uniformity is greatly reduced, which is consistent with the experimental results. The output radiance stability of the source is measured with an improvement from 8.4 × 10-5 to 2.7 × 10-5. Finally, the nonuniformity of the source is measured to be 0.15 % by a spot luminance meter.