为解决微小内轮廓尺寸为代表的微小尺寸的非接触式超精密测量问题,提出了将自聚焦透镜体积小的特点与共焦显微技术的高分辨率和绝对位置跟踪特性相结合的差动式自聚焦共焦微型显微技术的光探测技术,建立了相应的传感系统。介绍了系统的工作原理和构成,自聚焦透镜测头直径为1 mm,两个探测器差动设置,不但消除了光源的光强漂移和探测器的电子漂移产生的共模噪声,提高了测量信噪比,而且有效地提高了系统的轴向分辨率。初步实验表明,系统轴向分辨率在倾斜度小于20度的范围内可达5 nm。

For super high precision non-contact measurement of miniature cavities, an optical focus detection system is proposed based on a differential confocal microscopy. This system combines a high axial resolution and absolute position traceability of a confocal microscopy with a small gradient-index lens. The differential confocal principle and the system configuration are presented. In this system, the small detector with 1 mm diameter is obtained by a gradient-index lens, the noise produced by the light source intensity drift and the detector electronic drift is eliminated, and signal-to-noise ratio and axial resolution are increased by differential design of two detectors. Measurement made with 20° degree gauge block, with a detector of 1 mm diameter, axial resolution is up to 5 nm.