中文摘要：

本文将自动聚焦方法应用于激光诱导击穿光谱（LIBS）检测技术中，利用自动聚焦方法控制激光在样品表面的聚焦位置和焦斑大小，以克服激光诱导击穿光谱系统检测样品时光谱强度的起伏变化较大的缺点，提高LIBS系统重复测量的精密度。并采用灰度差分法评价函数和改进后的爬山法成功实现了激光诱导击穿光谱技术检测中焦点位置的自动搜寻和调节，为LIBS检测仪开发了一套自动聚焦系统和相应的软硬件，较好地减小了LIBS光谱强度多次重复测量的相对标准偏差。

英文摘要：

In order to overcome the shortage of the large variation of spectrum intensity in Laser Induced Breakdown Spectroscopy （LIBS） and to improve the measurement accuracy in term of the relative standard deviation of the line intensity from repeating measured spectrum, an auto-focusing system is integrated into the LIBS technique and used to control the size and position of the laser focus on the sample surface. Based on the gray level difference analysis method and a modified hill-climbing algorithm, an auto-focusing system, including hardware and software, is developed and used to automatically locate the laser focus point and then adjust the sample positions in LIBS measurements. The RSD of the repeating measurements is then improved.