白光扫描干涉过程的自动对焦方法研究

Research on Autofocus Algorithm for White Light Scanning Interference

摘要:

针对白光扫描干涉系统由于物镜景深小、干涉区间短而导致的调焦不准确、查找条纹困难、耗时长等问题,提出一种适用于白光干涉仪的自动对焦方法,该方法包括一种结合穷举法与爬山法的复合式对焦搜索算法,以及一种基于四叉树分解的粗精分步对焦评价函数。所提的搜索算法不需预先设定搜索范围,步长迭代可变,在能够快速搜索的同时具有较高的搜索精度和稳定性。所提的评价函数灵敏度较高,单峰性较好。实验结果表明,所提的自动对焦方法具有较高的对焦精度和速度,且能够在快速准确找到干涉条纹位置的同时,有效地避免由条纹以及环境噪声引起的对焦曲线多峰值问题。

Abstract:

To solve the problems that the white light scanning interference technology has objective lens with short depth of field and short interference interval, an auto focus method used for white light interferometers is proposed. The method includes a focus search algorithm combining exhaustive method and hill climbing method, and a focus evaluation function based on quadtree decomposition. The proposed search algorithm does not need to set the search range in advance, the step size is iterative, and it has high search accuracy and stability while being able to search quickly. The proposed evaluation function has higher sensitivity and better unimodality. Experimental results show that the proposed algorithm has high focusing accuracy and speed, and can effectively solve the multi-peak problem of the focusing curve caused by the fringe and ambient noise.