| 摘要 |
PURPOSE:To improve the C/N by using two pairs of photodetectors consisting of two photodetectors of different polarizing directions respectively together with a light detector provided to each photodetector to detect the light transmitted through the photodetector, a differential amplifier and an arithmetic circuit. CONSTITUTION:Two pairs of photodetectors consisting of two photodetectors respectively are used to calculated two outputs delivered differentially. For a photodetector pair A, a photodetector 42 is set at an angle -theta to the polarizing direction 18 with a photodetector 43 set at an angle +theta to the polarizing direction 17 respectively. The difference between both photodetectors 42 and 43 is set at DELTAIA. For a photodetector pair B, a photodetector 44 is set at -theta' to the direction 17 with a photodetector 45 set at +theta' to the direction 18 respectively. Then the difference between both photodetectors 44 and 45 is set at DELTAIB. The difference between DELTAIA and DELTAIB is set at DELTAI. The output of a differential amplifier is shown in a chart, wheretheta=theta' is satisfied. The maximum value is shown in the parentheses when theta=theta'=45 deg. is satisfied. The difference between H and L levels is defined as 8LthetaK from a figure (d), which is equal to the double as much as conventional 4LthetaK. Therefore the C/N is increased. |
