| 摘要 |
PURPOSE:To improve magnetic characteristics without flawing the insulating film of a grain oriented electrical steel sheet by providing a cylindrical mirror or lens at the entrance side of a rotary polygon mirror so that its axial direction is parallel to the axis of rotation of said polygon mirror. CONSTITUTION:A laser beam 1 is reflected by the rotary polygon mirror 2 and converted as a fine circular beam by a parabolic mirror 3 on the surface 4 of the grain oriented electrical steel sheet at a distance of focal length (f). In this case, when the cylindrical mirror 10 is arranged at the entrance side of the polygon mirror 2 so that its axial direction 10-1 is parallel to the axis 2-1 of rotation of the polygon mirror 2, the mirror 10 only reflects the laser beam 1 by its yz plane and converges it by its zx plane. Therefore, the laser beam 1 have different convergence positions in its scanning direction and a direction perpendicular to it and has a cross section shape shown in 12 in a figure on the copper plate surface 4 and a shape shown by 12 at a position 5 close to the copper plate surface 4. Therefore, an elliptic beam having its long axis in the scanning direction is formed on the steel sheet surface 4, so that a magnetic domain is fractionized without flawing the steel sheet 4. |
