The demand for high-accuracy measurement of micro-angle in modern industries is getting higher and higher, and its measurement methods and measurement technologies are also constantly improving. At present, The micro-angle measuring instrument with the highest accuracy in the world is the ELCOMAT HR photoelectric autocollimator produced by M?LLER-WEDEL in Germany, and its angle measurement uncertainty within the range of 300″ can reach 0.06″ (k=2). And the highest accuracy in China is the AUTOMAT 5 000 photoelectric autocollimator produced by Tianjin Automate Optoelectronics Co., which can achieve a measurement accuracy of ±0.25″ within the range of ±1 000". With the continuous improvement of the precision of micro-angle measurement, higher and higher requirements are put forward for the angle calibration, and some traditional angle calibration methods are difficult to meet the current needs. Therefore, using the self-calibration technology to realize micro-angle measurement has become a research hotspot in recent years. The current angle self-calibration technology mainly focuses on the measurement of the circumference angle with the characteristic of circle closure, and there are few studies on the self-calibration measurement of micro-angle. In the early stage, our research group proposed a micro-angle measurement system based on F-P etalon, which used the displacement of the concentric rings in the focal plane after F-P multi-beam interference ring imaging to achieve micro-angle measurement, and pointed out the possibility of using the system to realize the micro-angle self-calibration measurement. This paper provides a comprehensive review and summary of the self-calibration method for this micro-angle measurement. The key point of this self-calibration method is to use the exact fraction method to measure the exact value of the F-P etalon interval, and then accurately calculate the relative focal length of the imaging objective lens, and combine the relative displacement caused by the small angle, so as to realize the self-calibration of the micro-angle measurement. The main research work of this paper is as follows: 1) The principle and method of the self-calibration measurement of the micro-angle measurement system are systematically and detailedly sorted out, and the calculation method of exact fraction method is described in detail, and the complete micro-angle self-calibration measurement process is finally obtained. 2) Special consideration is given to the effect of the algorithm error of the exact fraction method, temperature and humidity on the measurement results of the F-P etalon. The interference image under the theoretical interval d0 is obtained through simulation by MATLAB, and the calculated interval d1 of the F-P etalon under this condition is obtained by using the exact fraction method, and compared with the theoretical interval d0, the algorithm error and the temperature and humidity error of the exact fraction method are obtained, and the correction of the calculation result of the F-P interval is realized. 3) The self-calibrated micro-angle measurement experiments are carried out, and the accurate interval of the F-P etalon in the current environmental conditions is measured. Combined with the simulation method in 1), the corrected value under the current environmental conditions is obtained, and finally the corrected etalon interval is obtained, which is d '=(2 014.986 5±0.000 3) μm. The focal lengths of the imaging objective and the micro-angle measurement results before and after self-calibration are obtained. The measurement results show that under the current experimental conditions, the relative expanded measurement uncertainty of the focal length after self-calibration has reduced from 0.014 to 0.007, while the angle measurement uncertainty in 600" has decreased from 0.132″ to 0.084″, which promotes the accuracy of micro-angle measurement greatly.
为了保证测量结果的可靠性,通常要对测量仪器的性能进行校准。然而随着高准确度微小角度测量技术的发展,对校准工作提出了越来越高的要求,一些传统的校准方法很难满足当前的需求。因此,采用自校准技术来实现高准确度微小角度测量同样成为了近年来的研究热点。2005年,俄罗斯AKSENENKO V D等[10]提出了一种基于双通道集成光谱误差的数字角度传感器的自校准系统,能将测角误差降低到6″。2010年,日本信州大学KOJIMA T等[11]研究了一种用于角度传感器的自校准技术,实现了0.2″的高精度测量。2011年,北京航天计量测试技术研究所[12]研究了一种差动式反光镜自校准系统,能够显著减小CCD自准直仪的示值误差,将其示值跳动量标准偏差降低至0.057 4″。2014年,德国GECKELER R D等[13]研究了一种角度编码器的自校准方法,用于在不依赖外部参考标准的情况下,对角度编码器快速精确校准,有望实现小于0.01″的测量不确定度。2016年,日本WATANABE T等[14]-15]研发出一种自校准角度编码器,能够实现刻度盘角度偏差和附件偏心误差的检测,其精度能达到约0.3″。2021年,中国计量科学研究院[16]提出了一种全圆连续角度标准装置,能够实现全周连续角度的实时测量和误差补偿,其全周范围内的测量不确定度逼近0.03″。
[10] AKSENENKOV D, MATVEYEVS I. Digital angle sensor self-calibration: two approaches to accuracy increasing[C]. IEEE Instrumentation & Measurement Technology Conference, IEEE, 2005.
[11] KOJIMA T, WAKIWAKA H. Study on high-precision angle sensor and angle measurement technology[J]. Electrical Engineering in Japan, 2010, 162(3): 68-77.
ZHANG Junjie, WANG Zheng, LI Zhengyang, et al. Self-calibration system for the value drifts of CCD autocollimator[J]. Acta Metrologica Sinica, 2011, 32(2): 123-125.
LI Gali, XUE Zi, HUANG Yao, et al. System error separation and compensation of the continuous full circle angle standard device[J]. Chinese Journal of Scientific Instrument, 2021, 42(3): 1-9.
LIU Yuan, SHEN Xiaoyan, ZHOU Shinan, et al. Micro-angle measurement method and its accuracy evaluation based on Fabry–Perot etalon[J]. Acta Photonica Sinica, 2021, 50(7): 0712004.
SHEN Xiaoyan, SUN Zhipeng, HU Jiacheng, et al. Method for measuring focal length of transmission objective lens based on F-P etalon[J]. Chinese Journal of Scientific Instrument, 2018, 39(5): 1-8.
LIU Songjiang, CHANG Ying, XIAO Zhigang, et al. Accurate calculation of the spacing of F-P etalon under the multi-wavelength weighted regression[J]. Infrared and Laser Engineering, 2011, 40(3): 529-532.
YU Jiayin, FAN Jing, LAN Xuhui, et al. Influence of reflection- induced retardance on the measurement of Fabry-Perot etalon interval[J]. Laser & Optoelectronics Progress, 2020, 57(9): 90-96.