| 摘要 |
PURPOSE:To eliminate the external noise by a method wherein the light resulting from the conversion of the discharge current of a gas laser tube by means of a light emitting diode is detected by a photo detector, and a feedback circuit which controls said current so that its value may become constant is provided. CONSTITUTION:One output end of a DC power source 1 is connected to the cathode 8 of the laser tube 4, and the other end is connected to the anode 9 of the tube 4 via a transistor 2 and a current detecting resistor 3, when the tube 4 discharges, and then a laser light 15 oscillates by photo resonators 5 and 5'. The discharge current between the anode and the cathode 8 is detected by the resistor 3, and the output voltage is supplied to the light emitting diode 11 via a resistor 10 and thus converted into a light proportional to said current. The light of the diode 11 is supplied to the photo detector 13 via an optical fiber cable 12. Here, the output voltage of the resistor 3 can be electrically connected directly to a comparator amplifier 6 via the cable 12, therefore the output noise does not mix in. |
