【作者】 叶瑞芳；

【导师】 黄元庆；

【作者基本信息】 厦门大学 ， 测试计量技术及仪器， 2009， 博士

【摘要】 随着精密加工和超精密加工技术的不断发展,激光与其他加工技术的复合逐渐成为加工制造领域的主流技术。在激光复合加工技术中,激光与水射流复合加工技术,即水导引激光加工技术是激光加工技术发展的一个新方向。与传统激光加工技术相比较,水导引激光加工技术具有加工距离长、热影响区小、无热熔渣和加工效率高等优势,已在微电子、航空制造、机械、医学等加工领域中得到应用。然而,现有的水导引激光加工技术采用传统聚焦透镜光学系统,不可避免地存在精密调焦、离焦发散角对耦合条件的影响以及聚焦光学系统的像差等问题。为了解决这些问题,基于轴棱锥镜产生的无衍射光束的中心光斑特性,本文首次将无衍射光束引入到水导引激光加工体系中,设计出了具有同轴监测功能的水射流导引激光加工系统的新方案。深入研究了水射流导引激光加工系统的光学特性、水光纤的流体力学特性及耦合系统的关键技术。利用水光纤波导导引无衍射光束,改变了激光束的能量高斯分布状况,实现了激光的能量近似平顶均匀分布,有效地改善工件加工质量,同时,利用本技术有效扩大了的加工范围,实现在二维平台对工件的三维加工。此外,设计了耦合装置,有效解决了无衍射光束与水光纤波导的耦合效率及传输损耗等关键技术问题。并提出一种新的无衍射光斑中心检测算法,提高了系统的监测精度。本文的主要创新点如下:1.首次把无衍射光应用于水导引激光加工系统。通过对轴棱锥镜产生无衍射光束的光学特性研究,利用无衍射光束具有中心光斑小,能量分布均匀,准直范围长的特点,采用轴棱锥镜替代现有水导引激光技术中的聚焦透镜的技术方案,彻底解决聚焦光学系统的调焦难题,降低了整个系统对设计、加工与调试精度要求;(专利受理号:200910111326.0)2.利用轴棱锥产生的无衍射光束在无衍射区域内光束发散角小,可把无衍射光近似于平行光的特性,有效地解决了激光与水光纤波导的耦合损耗关键技术。3.设计了加工、监测、指示定位三光轴同轴独特的光学系统(发明专利号:200710009244.7),简化了整机光学系统。本光学系统可实现了激光加工全过程的精确定位指示,并对激光与喷嘴耦合情况、水中气泡以及喷嘴的损坏等情况的实时监测;4.基于亚像素细分算法和边缘图像检测方法,提出了利用无衍射光束环栅的边缘信息对无衍射激光光斑中心的亚像素定位检测算法。实验结果表明,本算法实现了对无衍射光束光斑中心高精度定位,有效提高了系统的监测精度。更多还原

【Abstract】 With the development of precision machining and ultra-precision machining technologies, laser-hybrid processing technologies have gradually become the mainstream of manufacturing field. In terms of laser-hybrid processing technology, the combined processing technology of laser and water jet, namely the water jet guided laser processing technology, is a new direction of laser processing. Compared to traditional laser processing method, water jet guided laser processing technology, with its advantages of long working distance, small heat-affect zone, non-hot slag and high work efficiency, has been used in microelectronics, aviation machinery, medicine area, etc.However, owing to the utilization of traditional lens focus optical system in the existing water jet guided laser technology, the work of precision focusing, and the aberration of focusing optical system are unavoidable. To overcome these problems, based on the spot center characteristics of the non-diffracting beam generated by axicon, non-diffracting beam is introduced into water jet guided laser processing system for the first time, and a novel design of water jet guided laser processing system with coaxial monitoring function is proposed in this dissertation.The optical properties, and hydrodynamics characteristics, as well as the key coupling technologies between the non-diffracting beam and the water jet, have been deeply analyzed and researched. Using the transforming effect on non-diffracting beam through the water fiber, the Gaussian energy distribution of laser has been altered to a Flat-top energy distribution. This not only can improve the processing quality and satisfy the processing requirements, but also can enlarge the range of process and accomplish three-dimension process on a two-dimension platform. A coupling device is designed to solve the key technologies of coupling, such as the coupling efficiency and transmission loss between non-diffracting beam and water fiber. At the same time, a new algorithm for center location of non-diffracting beam is presented to improve the monitoring precision..The innovations of this dissertation are as follows:1. The non-diffracting beam is applied to water jet guided laser processing system for the first time. Through the research of the optical properties of the non-diffracting beam produced by axicon, a new method is proposed by use of the beam’s features, such as small spot, long scope of collimation and symmetry energy distribution, and so on. In this method, an axicon is used to replace the traditional lens. The focusing problem has been resolved and the accuracy requirements of overall system design, processing, and debugging have been reduced in this way. (Patent No. accepted: 200910111326.0)Due to small divergence angle for laser beam in non-diffracting region, the non -diffracting beam can be similar to the parallel light. With the advantage of the non -diffracting beam, the coupling loss between laser and water-fiber has been reduced.3. A special three-axis coaxial optical system of processing, positioning and monitoring is designed to simplify the whole system (Patent No.: 200710009244.7). The optical system can implement the precise positioning of the laser processing indicator and real-time monitoring for the coupling of laser and nozzle, the bubble in the water, as well as the damage of the nozzle.4. Based on the sub-pixel technologies and edge detection methods, by use of the edge information of ring beam, a sub-pixel locating algorithm to the centre spot of the non-diffracting beam has been established. The experimental results show that this algorithm can achieve a high-precision positioning detection on the non-diffracting beam centre spot, and improve the precision of the system monitoring更多还原