鉴于激光探针分辨率低的问题, 提出基于远场光学技术对激光探针仪的光学系统进行改进和设计, 实现了高分辨率激光探针仪的研制。研究了基于远场光学的激光探针仪的极限分辨率, 采用数值孔径为0.4的反射式聚焦物镜对波长为532 nm的脉冲激光束进行聚焦, 在合适能量条件下, 烧蚀Al和Fe纯样表面获得的极限分辨率分别为2.26 μm和1.87 μm, 在此极限分辨率下利用同轴光谱采集系统且能够采集到3倍于背景噪声强度的Al和Fe元素的光谱信号; 设计并实现了带同轴照明的同轴共焦成像系统, 视场放大率达24.7倍, 采用的同轴照明系统能够有效提高摄取图像的锐度和清晰度, 获得的图像分辨率不低于228 lines/mm; 发明了一种带指示光的同轴光谱采集系统, 能够将同轴光谱采集器与等离子体的对准误差控制在10 μm以内, 通过二维扫描装置, 实现对等离子体表面7×9的矩形点阵列进行精确光谱采集, 获得了等离子体原子光谱强度的空间分辨图像。

In order to improve the resolution further, the laser probe optical system was redesigned and optimized. The ultimate resolution of the laser probe based on far-field optics was studied. Using the reflex objective (N.A=0.4) to focus the incident 532 nm laser beam, under the condition of appropriate energy, the resolution of 2.26 μm and 1.87 μm on pure Al and Fe samples surface was obtained, respectively. Under this system, the effective Al and Fe atomic spectrum can be acquired with intensity three times of the background noise, respectively. A set of coaxial confocal imaging system with coaxial illumination was designed and realized, the field magnification is 24.7. The results showed that the coaxial illumination system can improve the sharpness and identification of the graphics with resolution not less than 228 lines per millimeter. A coaxial spectral collection system with indicator was invented, which can maintain the alignment error within 10 μm between the plasma and the coaxial collection system. In the coaxial monitoring area and combining with an X-Y axis scanning system, a spectra matrix with 63 points on the plasma surface can be acquired, which the images of plasma spatial resolution could be obtained.