10.6 μm CO2 레이저용 F-theta 렌즈의 설계 개발

Purpose: This study focuses on the design and development of an F-theta lens for a 10.6 μm CO2 laser. Methods: In order to design the F-theta lens satisfies the user's requirements that the diameter of the using laser beam is within 20 mm, the spot diameter of the imaging point is not more than 100 μm, the thickness of optical system is not more than 35 mm, the working distance is about 138.4 mm, and the effective imaging diameter is not less than 70.7 mm, we used eight variables that are four radii of curvatures, three distances between lens surfaces, and an effective focal length (EFL) to optimize the F-theta lens, after separating the two galvanomirror driving angles into eight states. Results: The optimized F-theta lens for CO2 lasers consists of two lenses in which the symbols of the refraction power are in the order of (−)(+). The characteristics of this system have the resolving line width of 5.0 lps/mm (@35% MTF value), the focal length of about 125.4 mm, the working distance of 138.4 mm, the effective imaging diameter of 70.7 mm, and the maximum galvanomirror driving angle of ± 5.73o. Conclusions: In this study, by the method of dividing the combination of two galvanomirror driving angles into eight states, and by using the eight variables consisting of four radii of curvatures, three distances which include the distance between lenses, the two thicknesses of lenses, and an EFL for optimization variables, we were able to develop the F-theta lens with the EFL of 125.4 mm for CO2 lasers, that could be used in laser marking machines or 3D printing equipments.