中文摘要：

采用Nd：YAG激光器产生的脉冲激光诱导击穿铜片形成等离子体，研究了透镜到样品表面距离的不同对激光诱导击穿光谱（LIBS）测量的影响．实验选择合适的延迟时间和采样门宽，并选用元素谱线λ（Cu）为324．8nm和327．4nm，λ（Zn）为330．3nm和334．5nm进行分析．实验结果表明，透镜到样品表面的距离对LIBS测量确实有很大的影响，谱线强度以及其相对标准偏差均与透镜到样品表面距离密切相关．透镜到样品表面的距离大于焦距时，空气击穿现象严重，不宜用于LIBS测量．激光脉冲能量大，透镜到样品表面距离对LIBS测量的影响大，激光脉冲能量小则相反．

英文摘要：

The plasma was generated from copper by a pulsed Nd. YAG laser, and the influence of lens-to-sample distance（LTSD） on measurement by laser-induced breakdown spectroscopy was investigated. The proper delay time and gate width were chosen, and several spectral lines such as λ（Cu） 324.8 nm and 327.4 nm, λ（Zn）330.3 nm and 334.5 nm were chosen for analysis. The experiment result shows that large influence of lens-to-sample distance on measurement by laser-induced breakdown spectroscopy exists, and the intensities and its relative standard deviation （RSD） of spectral lines inflict direct impact on the lens-to-sample distance. When the lens-to-sample distance was longer than the focal distance of lens, the phenomenon of laser-induced air plasma was severe and it wasn＇t equivalent to the measurement by laser-induced breakdown spectroscopy. The influence of lens-to-sample distance on measurement was longer when the laser energy was large, and vice versa.