Ryoichi KUWANO^1,2, Tsuyoshi TOKUNAGA³, Yukitoshi OTANI^1,4 and Norihiro UMEDA¹

¹Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan
²Mechanical Engineering Section, Fukuyama Polytechnic College, 4-8-48 Kitahonjo, Fukuyama, Hiroshima 720-0074, Japan
³Precision Engineering, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan
⁴College Optical Sciences, The University of Arizona, 1630E. University Blvd., Tucson, AZ 85721, U.S.A.

(Received August 24, 2005; Accepted August 31, 2005)

A method for a beam shaping optics is proposed to convert a laser beam profile into arbitrary required intensity distribution. Surface profile of the beam shaping optics is designed by using Snell's law to convert the required intensity distribution at the beam irradiation plane from the input intensity distribution. A computerized numerical control (CNC) lathe is employed to fabricate the beam shaping optics, and acrylic resin is used for the material. The acrylic resin plate is cut by a ball type of grinding wheel tool consisted on diamond powder and polished by a cone type felt buff with alumina ceramics powder. The CNC lathe is powerful tool to control the position of these tools. The fabricated beam shaping optics is aspheric shape with 4 mm of thickness and it works to convert the intensity distribution of multi-mode beam profile with 13 mm of diameter into a flat top cylinder with 1 mm of diameter. A working distance of the beam shaping optics is 60 mm, and its transmittance is over 98%. It succeeds to fabricate uniform melting mark of 0.6 mm diameter on a steel target by the YAG laser process.

Key words: beam shaping optics, aspheric lens, beam profile, CNC lathe, YAG laser