| 摘要 |
PURPOSE:To eliminate a background light noise by sending light from modulators which drive a couple of light emission source in mutually opposite-phase relation to a couple of photodetectors, and weighting and summing up photodetection outputs of the couple of photodetectors. CONSTITUTION:A transmit signal S to a terminal 101 is applied to a couple of modulators M1 and M2. The modulators M1 and M2 drive the couple of light sources L1 and L2 in mutually opposite-phase relation. Opposite-phase signals S and -S are emitted by the light sources L1 and L2 and noise light is radiated by the lighting almost uniformly from a wall 102, etc., at the circumference of the light sources L1 and L2. The directivity of the couple of photodetectors R1 and R2 is set to the light sources L1 and L2 respectively, and their photodetection outputs are weighted by K1 and K2 times through multipliers M10 and M20 and summed up by an adder 103. The wall 102, etc., are lighted normally by another light source 201 and its brightness varies uniformly over a wide area. The coefficients K1 and K2 are specified to remove the background noise component from the output of the adder 103, generating an output at a terminal 104. |
