Second-order acceleration for optical power measurement using axial thermopile detectors

• Published in: Measurement : journal of the International Measurement Confederation 2023-08, Vol.217, p.113006, Article 113006
• Main Authors: Li, Chaochen, Deng, Yuqiang, Zhang, Yunpeng, Ma, Chong
• Format: Article
• Language: English
• Subjects: Acceleration; Heat conduction; Laser power; Latency compensation; Optical radiometry; Response prediction
• ISSN: 0263-2241; 1873-412X
• DOI: 10.1016/j.measurement.2023.113006

•A physical model is established for axial thermopile detectors, and the theoretical response of the detectors is derived. The theoretical response is not completely described by a single exponential function (as commonly regarded by rough approximation), but a summation of infinite exponentials over time. Explanation is given that the adiabatic mechanism existing in light absorbing process is one of the intrinsic cause of the non-ideal exponential response of thermopile detectors.•The responses of detectors demonstrate significant deviation from the conventional first-order latency compensation process.•Based on the established model, a new latency compensation method with second-order differential operations is proposed to accelerate the response of thermopile detectors. In simulations, the second-order method theoretically shows 67% improvement, in comparison with the conventional method under same deviation ranges. In addition, an infinite-order acceleration algorithm is further constructed and extended to a variable coefficient form, which is theoretically complete for a perfect acceleration with arbitrary thermopile detectors.•Experiments are conducted. The advantages of the second-order method over the first order method with 23–65% improvements are verified.•The method is based on the adiabatic mechanism that generally exists in the light absorbing process. Therefore, the new method is compatible with various types of calorimetric detectors, including thermopile and thermal resistance. Since the measurement of optical power and irradiance is one of the most fundamental and common requests in optics-related fields, the method can have wide applications. A method of accelerating the response of thermopile detectors is proposed for optical power measurements. The physical model of the detectors is established, and the theoretical response is derived. The response is not completely described by a single exponential function. The difference between the conventional latency compensation method assuming a single exponential leads to overshoot and deviation from the equilibrium state. A new method with second-order differential operations is proposed, which is more appropriate for the non-exponential responses. In simulations, the second-order method theoretically shows 67% improvement in the measuring time. Experiments based on fabricated copper-substrate detectors show 43%, 65%, and 56% reduction in the measurement time compared with the conventional met