To simplify the circuit constitution of a processing circuit by reducing the number of light quantity detectors while maintaining the accuracy of the detection of a light quantity constant in an exposure device provided with the light quantity detectors for detecting the light quantity before starting exposure so as to make the light quantity of an exposure beam uniform at the time of performing scanning exposure with the exposure beam generated by using an optical modulation element.
The exposure device possesses a light transmissible sheet member 86 provided with a beam incident plane 82 extended in one direction in accordance with the extending direction of the exposure beam and a beam emitting surface 84 whose width in the extending direction of the beam incident plane 82 is narrowed because the shape of the beam incident plane 82 is deformed, and converges the exposure beams from the beam emitting surface 84 on the light receiving surface of the light quantity detector 90.
FUJII TAKESHI
NAKATANI DAISUKE
