Optical head device of a self-propelled type

1. Field of the Invention A head module contains a head motor, a reduction mechanism, and an optical head. The optical head is disposed behind an opening through which printing light is emitted toward an instant film. Both sides of the head module are provided with pinion gears rotated by the head motor via the reduction mechanism. A chassis is provided with rack gears respectively meshing with the pinion gears. The head module is reciprocated in a sub-scanning direction by the head motor. During the reciprocation of the head module, the printing light is emitted from the opening in accordance with image data to expose the instant film. A driving mechanism for the head module does not exist outside a movement range of the head module so that it is possible to downsize an instant printer using this head module.