To provide an illuminating optical device which can change the conditions of illumination almost continuously without substantially losing the quantity of light in a wave front split optical integrator.
An illuminating optical device for illuminating a surface (M) to be irradiated on the basis of a luminous flux from a light source (1) is provided with a wave front split optical integrator (6), which is arranged in an optical path between the light source and the surface to be irradiated and has a multitude of two-dimensionally arranged microscopic lens elements, and a light-leading optical system (7) arranged in an optical path between the optical integrator and the surface to be irradiated. A prescribed shape of a secondary light source, which is used as a virtual image, is formed at the position of the incident surface of the optical integrator via a relay optical system (5).
KOMATSUDA HIDEKI
TANITSU OSAMU
