An automatic real-time focus inspection system based on a combination of dynamic focusing and real-time focus detection is introduced for use in high-precision laser processing. The system allows for accurately and rapidly positioning the laser focus on the target surface, wherever it is located along the optical axis. The proposed method is superior to conventional methods because it not only offers accurate, versatile, and high-speed autofocusing, but also combines well with the fabrication laser to perform laser processing when the laser focus is located on the sample. In this system, the laser focus is flexibly and automatically shifted along the optical axis by a dynamic focusing device to rapidly meet the working surface, ensuring high quality and complexity of fabricated patterns. Thus, the laser focus is not restricted to the focal point of the objective lens of infinity corrected microscopes reported previously. Furthermore, the focal spot analytically maintains its size with a size deviation less than 0.1% while the focus is slightly shifted along the optical axis, guaranteeing the size and quality of fabricated patterns. The proposed method is expected to lead to a high-precision laser fabrication system that can be widely applied in both science and the industry.

We describe a new approach for locating the focal position in laser micromachining. This approach is based on a feedback system that uses a charge-coupled device (CCD) camera, a beam splitter, and a mirror to focus a laser beam on the surface of a work piece. We tested the proposed method for locating the focal position by using Zemax simulations, as well as physically carrying out drilling processes. Compared with conventional methods, this approach is advantageous because: the implementation is simple, the specimen can easily be positioned at the focal position, and the dynamically adjustable scan amplitude and the CCD camera can be used to monitor the laser beam’s profile. The proposed technique will be particularly useful for locating the focal position on any surface in laser micromachining.