弹流油膜光学测试系统的特性分析

Analysis of the Optical Characteristics of Optical EHL Film Measuring System

光干涉法是弹流润滑膜厚度测量的最有效的方法之一 .传统的理论认为光弹流干涉主要是双光束干涉 ,即光干涉强度是油膜厚度的余弦函数 ,通常应用该余弦关系分析弹流干涉图象 .然而 ,几个光弹流实验均表明干涉强度随油膜厚度的变化同余弦规律有明显的偏离 .应用薄膜光学理论对光弹流测试系统进行了分析 ,干涉强度的计算结果和实验数据吻合一致 。

Interferometry is one of the most efficient approaches for EHL film measurement. It is usually accepted that the optical EHL interference is a two beam one and the interference intensity changes with the film thickness according to a cosine wave, which has been used to reconstruct EHL film shapes. Nevertheless, several optical EHL experiments have demonstrated that the variation of intensity with film thickness can deviate from the cosine way obviously. The detailed analysis on the optical properties of the optical EHL measuring system has been given. The theoretical results and the experiments are in good correlation. It is shown that the deviation from the cosine wave mainly comes from the multi beam interference essence of the optical EHL system and the optical absorption of metallic medium.