| 摘要 |
PROBLEM TO BE SOLVED: To avoid influence due to reflected light and the influence due to noise such as diffused external light, without using a large-scale device or an expensive device. SOLUTION: The optical transmission part 4 of a master unit 1 common-mode transmits transmission lights LPa and LPb of different light emission spectrums from LEDs 14 and 15, corresponding to signals P to be transmitted. In the optical reception part 6 of a slave unit 2, the transmission lights LPa and LPb are converted photoelectrically in a PD 37, and only the signals P are extracted by an operation in an operational amplifier 38. Also, a signal transmission part 5 of the slave unit 2 differentially transmits the transmission light beams (-LCb and LCa) of different light emission spectra from the LEDs 31 and 33, corresponding to the signals C to be transmitted. In the optical reception part 3 of the master unit 1, the transmission light beams (-LCb and LCa) are converted photoelectrically, corresponding to the light emission spectrums by the PDs 12 and 13, and only the signals C are extracted by the operation in the operational amplifier 11. |
