Basic Research on Rotary Liquid Lens for Laser Beam Shaping

• Main Authors: Chen, Hao-Jen, 陳顥仁
• Other Authors: Kuo, Chia-Lung
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/37797967061944769527

碩士 === 國立雲林科技大學 === 機械工程系 === 104 === In this research, we proposed the rotary liquid lens applied to generation of the bifocal laser mechanism. After getting focused, the Gaussian beams was input to the rotary liquid lens which shell was composed by aluminum with window on both the top and bottom for laser to penetrate through and package two types of liquids. Then, by means of the different densities, the two types of liquids, silicon oil and water that are incompatible with each other and have different refractive index, were centrifuged into the inner and outer layers. With input of the beams, optical path length difference was generated, forming two coaxial beams with divergent focal lengths; that is, Peripheral Rays, beam penetrable water with low intensity surrounding the Gaussian distribution; and Paraxial Rays, beam penetrable silicon oil with high intensity in the middle of the Gaussian distribution. With Peripheral Rays and Paraxial Rays, bifocal laser was generated and achieved the function of beam-shape. Before the experiment began, the software of COMSOL Multiphysics 5.0 was adopted to assist in this research. By simulating different refractive index and the positions to place the liquid lens of configurations, the beam's axial intensity distribution, the beam's radial intensity distribution, and the focal spot locations were extracted. Finally, on the basis of simulated allocation, we designed and processed the liquid lens and the revolving mechanism. According to the bifocal laser applied to AA5052 aluminum of the basic research results, bifocal laser processing range increase an average of 177-225 μm to the diameter in comparison with the traditional Gaussian laser. In addition, the spots vibration has caused expansion of the processing range and reduction of the depth. In comparison to the traditional Gaussian laser, the surface roughness has reduced Sa 3.33 μm to 5.33 μm. For surface heat treatment of the low carbon steel JIS G3141, Vickers hardness can achieve up to HV 364.04, about an average of 21.22% is raised compared with the traditional Gaussian Laser, and 95.02% is raised for untreated hardness. As for polishing the surface of TI6Al4V, the surface roughness can be reduced to a minimum of Sa 0.616 μm. In short, such research results can not only serve as the innovative application mechanism for the optical element, the lens can also be applied to surface Melted, surface polishing, or the periodic structure produced by the property of vibration. In the future, controlling different rotational speeds of the silicone oil will be able to demonstrate different curve profiles and the focal lengths.