Patent ID: 6507424
Filing Date: 2003-01-14
Classification: H04B

Abstract:
An optical space communication apparatus for use in a system for performing communication among a plurality of optical space communication apparatuses, said optical space communication apparatus comprising:a first photodetector for detecting a light signal transmitted from another optical space communication apparatus having a light emitting device generating the light signal; a second photodetector for detecting a spot position of an incoming light beam including the light signal and a background light; an optical system having an optical path for guiding the incoming light beam; light beam splitting means for splitting the incoming light beam into a first light beam directed to said first photodetector and a second light beam directed to said second photodetector; switching means provided in the optical path of said optical system between said light beam splitting means and said second photodetector and adapted for switching between a first state, where only the background light in the second light beam is detected by said second photodetector and the light signal is intercepted, and a second state, where the light signal and the background light are both detected by said second photodetector; a memory for storing an output of said second photodetector in either one of the first state and the second state; a subtracter for executing subtraction between the output of said second photodetector stored in said memory and an output of said second photodetector in the other one of the first state and the second state, and outputting a subtraction signal resulting from the subtraction; and tracking means for tracking the light signal based on the subtraction signal output from said subtracter while the light emitting device of the other optical space communication apparatus is maintained in an on state.