To provide an illuminating optical device, capable of forming an illuminating region, provided with illuminance distribution suitable for scan alignment, while satisfactorily suppressing light quantity loss.
This device is provided with many luminous flux superimposing means (5 and 7) for forming many light sources, based on luminous fluxes from a light source means (1) and forming an irradiation field, which is an area on a prescribed surface, where the luminous fluxes from many light sources are superimposed and a light guide optical system (10) for guiding the luminous fluxes from the irradiation field to a surface (11) to be irradiated. Then, a first diaphragm (8) is arranged on the prescribed surface, and a second diaphragm (9) for stipulating an illuminating area to be formed on the surface to be irradiated is arranged at a position, optically conjugate to the surface to be irradiated. The first diaphragm (8) and the second diaphragm (9) are substantially arranged with an interval along the optical axis.
TANITSU OSAMU
KUDO YUJI
