To form a light source distribution composed of an arbitrary light intensity distribution in an arbitrary area, by adjusting the reflecting angles of a plurality of two-dimensionally constituted small mirror surfaces in accordance with an external drive signal by adjusting the intensities of reflected light rays from arbitrary positions on the light reflecting surfaces to arbitrary values in a certain specific direction.

A deformable illumination filter 2 carries many small mirrors 2a on the flat surface of a substrate 2B, and reflected light rays from the mirrors 2a form an optically filtrated luminous flux when the reflecting angles of the mirrors 2a are adjusted in accordance with an external drive signal. The mirror surface of each small mirror 2a is constituted two-dimensionally and the reflecting angle of each mirror surface is adjusted in accordance with the external drive signal. In addition, each mirror 2a is journaled at both ends of a diagonal line dg on the substrate 2B and the reflecting angle of the mirror 2a is changed in accordance with a drive circuit 11a to output reflected light having an arbitrary light intensity distribution. Therefore, the reflected luminous flux from the light reflecting surfaces of the mirrors 2a is optically filtrated, and a desired light intensity distribution can be given to the luminous flux.