| 摘要 |
PURPOSE:To measure very weak light continuously and accurately, by controlling the amount of light of an LED at a constant value by the output of a photodiode, and guiding the light of the LED to a photoelectric multiplier tube through a chipper 5'. CONSTITUTION:A constant current having a specified period determined by a timer IC12 of a power source 8, resistors 13 and 14, and a capacitor 15 is supplied to the LED 1 in a reference light box 7, and the LED1 is intermittently flashed. The photodiode 2 receives said light. The output current of the photodiode 2 is smoothed by a capacitor 16 and inputted into an IC18. The output of the IC18 is fed back to a transistor 19, which controls the current of the LED1, and the amount of the light is kept at the constant value. The light of the LED1 is guided to the photoelectric multiplier tube 4 through an optical fiber 3. The output of the tube 4 is adjusted by a variable resistor and the sensitivity is calibrated. The light of the LED1 is guided to a spectroscope 5 through the optical fiber and a chopper 5'. Te emitted light from the spectroscope 5 is detected by the photoelectric multiplier tube 4 and the result is guided to a measuring circuit 11. In this constitution, the very weak light is measured continuously and accurately. |
