Patent ID: 6928198

Claim:
An exposure head which is moved relative to an exposed surface in a direction orthogonal to a predetermined direction, comprising: a laser device which has a plurality of fiber light sources for emitting laser light incident from optical-fiber incident ends thereof, from output ends thereof, and in which luminous points at the optical-fiber output ends of the plurality of fiber light sources are arranged; a modulation means which is capable of changing a modulation state of laser light, in accordance with a control signal, for each of pixels thereon which have been arranged in a two dimensional manner; and an optical system for imaging laser light outputted from the laser device and modulated at pixel portions of the modulation means onto the exposed surface, wherein parameters defined as follows satisfy the following formula, D A 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.