Patent ID: 7061517

Claim:
An image exposure method in which an exposure head is moved relative to an exposed surface in a direction orthogonal to a predetermined direction, comprising the steps of: (a) employing a laser device in which luminous points at output ends of optical-fibers of a plurality of fiber light sources are arranged, and emitting laser light incident from incident ends of the optical fibers, from output ends thereof; (b) employing a modulation means having pixels arranged thereon in a two dimensional manner, and changing a modulation state of laser light, in accordance with a control signal, for each of the pixels; and (c) imaging laser light of which modulation state has been thus changed onto the exposed surface by an optical system, wherein, in the steps (a) to (c), parameters defined as follows satisfy the following formula, D W ≤ α × M 2 × t - K × λ a θ λ: the wavelength of laser light θ: the angle of beam outputted from optical fiber that is derived by a numerical aperture (NA) of optical fiber according to the following formula θ=sin −1 (NA) D: the width of beam outputted from the laser device W: the beam width at the position of the modulation means (at the irradiated surface) a: the size of one pixel on the modulation means K: a coefficient determined by beam characteristics, K=1 M: the magnification of imaging optical system t: required focal depth α: acceptable increased amount of beam diameter.