Patent ID: 7239811

Claim:
An optical-axis directional indicating apparatus for optical communication comprising: a base rotatable about a first axis that vertically passes through the base; a photoreceptor mounted on the base, the photoreceptor having a light-receiving surface that is rotatable about a second axis orthogonal to the first axis and a first optical receiving element, a second optical receiving element, a third optical receiving element and a fourth optical receiving element, to receive a transmitted light beam, the first and third elements being aligned on the surface in a first direction and located opposite each other in the first direction and the second and fourth elements being aligned on the surface in a second direction parallel to the second axis and orthogonal to the first direction and located opposite each other in the second direction with the first and third elements interposed between the second and fourth elements; a detector to detect levels of the light beam received at the optical receiving elements; a plurality of display elements arranged in the first and second directions so as to correspond to the optical receiving elements of the photoreceptor; and a switch circuit to selectively turn on or off the display elements in accordance with the levels of the light beam detected by the detector, to indicate whether or not an optical axis of the light beam is deviated in the first and/or the second direction on the light-receiving surface of the photoreceptor.