To adjust a beam size in the long and short-axis directions for each direction, and also allow the beam to be irradiated at a uniform intensity.
A variable beam size illumination optical device has a beam size varying optical system. The system includes cylindrical array lens groups 10a, 20a arranged corresponding to each of the long and short axis directions and having variable intervals between the respective lenses, and a cylindrical telescope lens group 30a arranged corresponding to one of the long and short axis directions and having variable intervals between the respective lenses. The system changes the size in the two-axial directions perpendicular to each other with respect to parallel light entering from a light source 1. The lens interval of either one of the cylindrical array lens groups 10a, 20a and the cylindrical telescope lens group 30a is changed (Db) so as to change the beam size in the long-axis direction or in the short-axis direction on a projection surface 9 for each direction.
AOYAMA HIROSHI
MARUYAMA SHIGENOBU
YOSHITAKE YASUHIRO
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