A light-projecting device comprises a superimpose-plate, which is put on a focusing
glass. A hollow pentagonal mirror has a roof reflecting plane, reflecting a light
beam passing through the focusing glass and the superimpose-plate, a third reflecting
plane, reflecting the light beam reflected on the roof reflecting plane, and an
emergent opening through which the light beam reflected on the third reflecting
plane passes. An illumination light beam output from a light source of a light-projecting
optical system is reflected on a light-projecting prism, and radiated from the
emergent opening to the third reflecting plane. The illumination light beam is
reflected on the third reflecting plane and the roof reflecting plane, and is approximately
perpendicularly radiated on the superimpose-plate.
