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在光镊系统中通常利用四象限位置探测器(QPD)进行位移测量,QPD的输出电压-粒子位移标定一直是影响位移测量精度的主要因素。论文研究了一种在光镊中基于QPD的输出电压-粒子位移标定方法,用QPD记录粒子移动时的电压信号,同时用CCD测量粒子的位移,比较电压峰峰值和位移峰峰值求得电压-位移转换系数。基于该标定的转换系数可快捷、实时的测量光镊系统中的粒子位移。搭建了光镊系统,并测量了放大倍数为120时的QPD输出电压-粒子位移转换系数,Y轴方向的转换系数平均值为0.1186v/μm,不稳定性低于1%,证明了该方法的有效性。进一步分析了影响转换系数标定精度的因素,包括系统放大倍数、粒子光斑大小、粒子纵向深度变化等。
In the optical tweezers system, the displacement measurement is usually performed by the QPD. The output voltage of the QPD - particle displacement calibration has always been the main factor affecting the accuracy of displacement measurement. In this paper, we study a QPD-based output voltage-particle displacement calibration method in optical tweezers. The voltage signal is recorded with QPD and the displacement of the particles is measured by CCD. The voltage peak-to- Displacement conversion factor. Based on the calibration conversion coefficient can be fast, real-time measurement of optical tweezers system particle displacement. The optical tweezers system was built and the QPD output voltage-particle displacement conversion coefficient at 120 magnification was measured. The average conversion coefficient of Y-axis was 0.1186v / μm, and the instability was less than 1% Effectiveness. Further analysis of factors affecting the conversion coefficient calibration accuracy, including the system magnification, particle spot size, particle depth changes and other vertical.