DETECTOR OF NUMBER OF REVOLUTION, SPEED, OR THE LIKE

摘要

PURPOSE:To perform high-reliability measurement under an electromagnetic noise and make the optical axis alignment work unnecessary to eliminate the impossibility of measurement due to the deviation of optical axis, by leading an electromotive force, which is generated in a coil when a moving magnet passes it, to a light intensity modulating element. CONSTITUTION:A coil 30 is fixed near an optional point of the locus of a circularly moved magnet 11 so that this coil 30 is linked sufficiently to the magnetic flux generated from the magnet 11. The light intensity modulating element includes two optical waveguides 21 and 22 formed on a substrate 20 consisting of a crystal having the electrooptic effect, for example, an LiNbO3 crystal. A pair of electrodes 31 are provided on parts close to each other of optical waveguides 21 and 22, and a voltage induced in the coil 30 is applied to these electrodes 31. The optical signal led to the optical waveguide 21 through an optical fiber 41 has the intensity modulated and is led to an optical fiber 42 and is converted photoelectrically by a photoelectric transducer 43 and is inputted to a counter 46 through a low pass filter 44 and a level discriminating circuit 45 to obtain a detection signal indicating the number of revolution of a disc 10.