Light beam scanning apparatus

摘要

A high-resolution light-beam scanning apparatus utilizing only mass-producible holograms instead of utilizing auxiliary optical systems such as optical lenses or a mirror having curvature, and capable of compensating for disadvantages including scanning beam thickening and variation, failure of a rotatable hologram to rotate at a constant velocity, displacement of a scanning beam position in the scanning direction and the cross scanning direction due to a mode hop of a wavelength of a semiconductor laser, and deviation of a base of rotatable hologram from a parallel state. These disadvantages are detrimental to efforts for increasing the resolution of a hologram scanner and lowering the cost thereof. The light beam scanning apparatus includes at least two holograms with one being fixed and the other rotatable, where a rate of variation of a direction cosine of an object wave recorded on the fixed plate and taken in a scanning direction of the light on the scanning surface is configured to be different from a rate of variation of a direction cosine of the object wave recorded on the fixed plate and taken in a cross scanning direction of the light on the scanning surface, and focal distances of a light incident on said rotatable hologram are configured to be different in the scanning direction and in the cross scanning direction.