LIGHT IRRADIATION DEVICE

PROBLEM TO BE SOLVED: To provide a light irradiation device that includes an illuminance adjustment mechanism in which center illuminance of a surface to be irradiated is adjusted while an amount of light which an object to be processed receives is maintained to be constant in a light irradiation device including a pair of trough type mirrors surrounding a linear light source.SOLUTION: A pair of trough type mirrors are counter-arranged on a cross section M that is orthogonal to a central axis C of an illuminant to open to be V-shaped, and configured to be mutually symmetric to be rotatable relating to a mirror symmetry plane A that includes the central axis C and orthogonal to a surface to be irradiated centering a turning shaft R formed in a space between the illuminant and the trough type mirrors. In the pair of trough type mirrors, illuminance adjustment is performed by that the mirrors are rotated in an opening direction or a closing direction based on an angle α selected in an angular range between an angle α1 that corresponds to an open state in which center illuminance in the surface to be irradiated becomes the maximum is assumed to be a lower limit, and an angle α2 that corresponds to the maximum open state in which the mirror does not contact a structure component that composes a light irradiation device housing is assumed to be an upper limit.