| 摘要 |
PROBLEM TO BE SOLVED: To obtain an illumination device that an illumination optical system can be small-sized in an optical axis direction without making the size of one frame of a lens array small by providing it with a first optical element where plural positive lenses are arranged, a second optical element where plural negative lenses are arranged and a third optical element where the plural positive lenses are arranged. SOLUTION: The firs lens array (first optical element) 2 is constituted by arranging the plural lenses 2a having positive refractive power on a plate. The second lens array (second optical element) 3 is constituted by arranging the plural lenses 3a having negative refractive power on the plate. The third lens array (third optical element) 4 is constituted by arranging the plural lenses 4a having the positive refractive power on the plate. By constituting the part of the lens arrays of three lens arrays 2-4 having the refractive power of the positive, the negative and the positive in turn from a light source 1 side in such a way, the part of the lens arrays can be small-sized in the optical axis direction. |
