柴油机喷雾场数字图像测量的误差分析

Measurement Error Analysis for Digital Image of Diesel Fuel Spray

分析了柴油机喷雾场光学测量中关键参数的基本要求和取值范围与测量系统的主要误差来源及计算公式。分析认为CCD光电转换特性、像素当量值的舍入、照明光线的变化等引起的随机误差影响较小,并可采取多次采样取平均值的方法进一步减小其影响;实验台振动导致的摄像镜头在平行于焦平面上的微量偏移引入的测量误差很小,而摄像镜头在光轴方向上的偏移,即物距的变化将带来较大误差,应尽量避免;图像畸变引起的误差对测量系统的精度影响很大,采用定标校准的方法能对该项误差进行有效的修正。

The basic requirements and the practical value range of the key parameters in the optical measurement of diesel fuel spray are analyzed. The main error sources of measuring system and their calculating formulae are presented. It is held that the random errors caused by the photoelectric conversion characteristic of CCD, the caused by test bench oscillation produces a rather small error, while the fore-and-aft shake of camera lens along optical axis will introduce greater error and needs to be avoided. The image distortion will also cause unacceptable error, but can be effectively corrected by system calibration.