| US 7,489,871 B2 | ||
| Light detection apparatus and free space optics communication apparatus | ||
| Yasuhiro Takahashi, Saitama-ken (Japan); Ryuji Ohmuro, Tochigi-ken (Japan); and Tetsuo Sakanaka, Kanagawa-ken (Japan) | ||
| Assigned to Canon Kabushiki Kaisha, Tokyo (Japan) | ||
| Filed on Dec. 08, 2004, as Appl. No. 11/7,364. | ||
| Claims priority of application No. 2003-412522 (JP), filed on Dec. 10, 2003. | ||
| Prior Publication US 2005/0141897 A1, Jun. 30, 2005 | ||
| Int. Cl. H04B 10/00 (2006.01) | ||
| U.S. Cl. 398—129 [398/131] | 5 Claims |
| 1. 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.
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