Rhee Hyug-Gyo, Kim Dong-Ik, Lee Yun-Woo
Space Optics Research Center, Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea.
Rev Sci Instrum. 2009 Jul;80(7):073103. doi: 10.1063/1.3176468.
The autofocusing is one of the important parts in the automated vision inspection or measurement using optical microscopes. Moreover, laser micromachining or laser lithography requires a high speed and precision autofocusing. In this paper, we propose and realize an autofocusing system using two cylindrical lenses, which is the enhanced version of the previous astigmatism method. It shows very good performances, especially very high speed and the largest range in comparison with the previous astigmatic methods. The performance of our autofocusing system was evaluated by tracing the linear stage whose position was monitored by a commercial laser interferometer. Then we applied the autofocusing to the direct laser lithographic system, and successfully fabricated circular symmetry patterns on a 300 mm diameter surface with the resolution of less than 1 microm within the defocusing range of +/-50 microm. The speed of the autofocusing was 150 Hz.
自动聚焦是使用光学显微镜进行自动视觉检测或测量的重要组成部分之一。此外，激光微加工或激光光刻需要高速且精确的自动聚焦。在本文中，我们提出并实现了一种使用两个柱面透镜的自动聚焦系统，它是先前像散法的增强版本。与先前的像散法相比，它表现出非常好的性能，特别是非常高的速度和最大的范围。我们的自动聚焦系统的性能通过跟踪线性平台来评估，该线性平台的位置由商用激光干涉仪监测。然后我们将自动聚焦应用于直接激光光刻系统，并在直径300毫米的表面上成功制造出圆形对称图案，在+/-50微米的离焦范围内分辨率小于1微米。自动聚焦的速度为150赫兹。
