为了精确测量长焦距光学元件的焦距, 分析了基于 Talbot-Moiré技术测量长焦距光学元件焦距的基本理论。设计包括准直光源, Talbot干涉仪和图像采集系统的实验装置, 通过实验分析得到系统测量精度的影响因素。以焦距值达到几百米的光学元件的焦距测量为目标, 构建了系统测量不确定度的数学模型。利用合成不确定评定方法, 实验得出系统测量不确定度随着待测焦距的增加逐渐增大, 当待测系统焦距达到 500 m时, 相对测量不确定度为 5.23%(k=2)。实验测量参考焦距为 75 272.80 mm的光学系统, 测量相对偏差为 1.09%。

To achieve accurate measurement of focal length of lens and optical system, the measurement theory based on Talbot-Moiré is analyzed. The system includes a collimated light generator, two Ronchi gratings and an image acquisition system. The theoretical issues and deviation are analyzed. The measurement uncertainty also increases with the increase of the focal length under test. When the focal length of lens under test is 500 m, the measurement uncertainty is 5.23%. The optical system whose focal length is 75 272.80 mm is measured, and its measuring relative deviation is 1.09%.