Research On Focus Controlling System Based On Image Processing

With the development of pulse laser micro machining technology and increasingly higher requirement for machining accuracy, the laser processing system needs an improvement. Moreover, in order to achieve some special processing, flexible focus controlling technology becomes one of the topics of improving processing results. The purpose of this paper is to increase the focus control system in laser micro-processing system, so as to improve and expand the processing performance and capability of laser micro-machining system.In this dissertation a set of focus controlling system for laser micro machining is designed. The system mainly included lighting source, laser source, optical system, imaging & control unit and one dimensional moving platform, etc. The 355nm UV nanosecond laser is applied as laser source. The co-axial con-focal zoom lens and apochromatic objective lens from Navitar Company composed optical system which can solve the con-focal problem between laser focal plane and imaging focal plane. The imaging & control unit, which used CMOS as the imaging device, and used DSP with CPLD as controlling unit, drove the one dimensional platform moving in axis direction for focus controlling. The experiments show that this system could accomplish the focus controlling with certain accuracy.The main works of this dissertation as follows:1. Based on the principle of image optics and image processing, the focus controlling system is designed.2. The hardware system is designed and debugged, which based on CMOS, CPLD and DSP.3. The system software is programmed and debugged, including image unit and control unit.4. The focus controlling system is built, and some of experiments are done with the system. And then the focusing criterion of the control system is studied and the focus accuracy is tested.