| 摘要 |
The present invention is aimed at providing a wavefront dividing type optical integrator which can yield a uniform illuminance distribution substantially over the whole illumination field formed thereby even when the size of each micro lens constituting the optical integrator is made smaller so as to set a large number of wavefront divisions. The optical integrator in accordance with the present invention is a wavefront dividing type optical integrator, having a number of micro lenses arranged two-dimensionally, for forming a number of light sources by dividing a wavefront of an incident beam; each micro lens having a rectangular entrance surface and a rectangular exit surface, and satisfying at least one of the following conditions:where f is the focal length of each micro lens, d1 is the length of one side of the entrance surface of each micro lens, d2 is the length of the other side of the entrance surface of each micro lens, D1 is the length of the side of exit surface in each micro lens corresponding to the one side of entrance surface, D2 is the length of the side of exit surface in each micro lens corresponding to the other side of entrance surface, and lambda is the wavelength of the incident beam.
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