Patent ID: 7489871

Claim:
A free space optics communication apparatus which performs communication with a target apparatus through a light flux propagating in space, comprising: an optical system which includes a light receiving element; a light converging optical system which guides the light flux incident from the target apparatus to a light receiving surface of the light receiving element; a drive mechanism which drives the optical system; and a drive circuit which controls the drive mechanism based on output from the light receiving element, wherein the light converging optical system converges the light flux incident from the target apparatus on each of a first light convergent point and a second light convergent point on substantially a same optical axis, the light receiving surface of the light receiving element is placed between the first and second light convergent points in a direction of the optical axis such that a spot formed on the light receiving surface by the light flux passing through the first light convergent point and a spot formed on the light receiving surface by the light flux directed toward the second light convergent point have substantially the same sizes, and the drive circuit controls the drive mechanism based on information on position of the spot on the light receiving surface.