共焦拉曼技术结合了共焦显微技术和拉曼光谱技术, 具有高分辨率、 高灵敏度、 可层析成像的优势, 广泛应用于物理、 材料科学、 生物医学、 文物鉴定以及刑侦等领域。 由于拉曼光谱成像需要较长时间, 测量中系统易受环境等因素影响产生漂移, 造成离焦, 而现有商用共焦拉曼光谱仪并无定焦能力, 容易影响测量结果。 针对此问题, 研制了一种具有抗漂移能力的激光共焦拉曼光谱探测系统。 在不改变共焦拉曼探测基本原理的基础上, 利用拉曼轴向响应曲线最大值对应显微物镜焦面这一特性, 对每个探测点进行轴向扫描, 采集一定数量的轴向信号, 通过曲线拟合寻找光谱强度极值位置, 保证扫描过程中样品始终处于系统的焦点位置处, 抑制离焦影响, 改善拉曼光谱成像效果。 以单层石墨烯样品进行单点测试, 证明仪器在5 μm离焦范围内可以实现实时定焦, 定焦后采集到的拉曼光谱强度几乎不变, 具有良好的抗漂移能力; 对硅台阶样品进行成像测试, 结果表明成像过程中, 信号强度未发生明显变化, 且横向分辨率有一定改善, 效果明显优于普通共焦拉曼光谱探测系统。

Confocal Raman technique, which combines confocal microscopy and Raman spectroscopy techniques, plays an important role in the field of physical science, material science, biomedical and cultural relics identification, criminal investigation with high resolution, high sensitivity, and the advantages of tomography. The existing commercial confocal Raman spectrometers have no fixed focus ability so that the sample table drift caused by defocus often appears in the measurement, which affects the measurement results. In view of this problem, a laser confocal Raman spectroscopy detection system with anti-drift capability was developed in this paper. Based on the confocal Raman detection principle, this system could realize auto focus by using Raman axial response curve of the maximum confocal position of the corresponding samples. The spectral intensity extremum position was obtained by curve fitting, and it realized the real-time location of measured samples at the confocal position to improve the effect of Raman spectral imaging. In this paper, we used the single layer graphene samples for single point test and the auto focus could be realized in 5 μm, and the intensity we got has almost no changes. We can say the system has a better ability of anti-drift. We got Raman imaging of silicon step samples. We could find that it had stable single and better lateral resolution, which was obviously superior to the conventional confocal Raman spectrum detection system in long time measurement.