基于阈值判定法的白光干涉仪自动扫描技术研究

摘要

为了解决实际操作中人工寻找干涉条纹费时、不准确和干涉扫描范围难以精确确定等问题,提出了一种自动扫描技术,实现了白光干涉仪的自动对焦和干涉扫描范围的自动确定。该技术采用全新的基于图像灰度方差变化的方法。首先,计算图像灰度方差变化比值;然后,将该比值与预先设定的阈值进行比较,判断干涉条纹初始和结束位置;最后,根据这两个位置自动确定干涉扫描范围。实验证明：当阈值取0.5时,采用粗精双级结构的白光干涉仪能在3min内准确完成1.2μm被测高度的自动扫描过程,约是手动调节速度的两倍。该技术提高了白光干涉仪的自动化水平及使用效率。%In order to overcome the inefficiency and low precision of manual search for interference fringes and the difficulty of determining interference scanning range, a new kind of automatic scanning technology was put forwarded. It could realize auto--focus, and it can also determine the interference scanning range of the white--light interferometer. The technology, based on the image gray variance change included the following steps： first, computing the image gray variance change ratio; second, comparing this ratio with the predetermined threshold,then judging the initial and ending positions of the interference fringes; and finally, determining the interference scanning range according to the two positions. Experiments show that,when the threshold of the used method is set as 0.5, the interfer- ometer which has coarse and fine double level of driving structure can complete automatically scanning process of the height of 1.2μm in three minutes accurately, two times faster than manual adjustment. This technique can improve the efficiency and automation level of the white--light interferometer.