Patent ID: 7927421

Claim:
A light irradiation apparatus which irradiates an irradiation target plane with light having a predetermined light intensity distribution, comprising: a light modulation element having a light modulation pattern of a periodic structure represented by primitive translation vectors (al, a 2 ); an illumination system which has an exit pupil and, illuminates the light modulation element with the light; and an image forming optical system disposed between the light modulation element and the irradiation target plane to form the predetermined light intensity distribution of the light obtained by the light modulation pattern on the irradiation target plane, wherein a shape of the exit pupil of the illumination system is analogous to the Wigner-Seitz cell of primitive reciprocal lattice vectors (bl, b 2 ) obtained from the primitive translation vectors (al, a 2 ) by the following equations: b 1=2π( a 2× a 3)/( a 1·( a 2× a 3)) and b 2=2π( a 3× a 1)/( a 1·( a 2× a 3)) in which a 3 is a vector having an arbitrary size in a normal direction of a flat surface of the light modulation pattern of the light modulation element, “·” is an inner product of the vector, and “×” is an outer product of the vector.