When a Gaussian power distribution laser beam is converted into a uniform power
density beam by a converging homogenizing DOE and is divided into a plurality of
homogenized beams by a diverging DOE, the power of the separated beam spatially
fluctuates. For alleviating the power fluctuation of the beams, an aperture mask
having a window wider than a section of the homogenized beam but narrower than
a noise region at a focus of the converging homogenizer DOE. Since a homogenized
beam can pass the aperture mask as a whole, the power fluctuation, in particular,
near edges is reduced.
