METHOD AND DEVICE TO MEASURE PHYSICAL VALUE OF LIGHT-SCATTERING MOVEMENT PARTICLE BY LASER DOPPLER FLUID SPEEDOMETER

摘要

PROBLEM TO BE SOLVED: To provide a method and a device for generating a moving superimposed signal whose brightness is modulated in a quantity to be measured of LDA on the basis of simple driving of a phase modulator. SOLUTION: A phase modulator is driven by two sine driving signals in different frequencies (ω1 andω2 ) jointed together so as to be fixed on a phase and a frequency, and one frequency (ω2 ) is an integral magnification of the other frequency (ω1 ), and a filter frequency (fF) being a common multiple of the two frequencies (ω1 andω2 ) is filtered from an output signal of a receiver 4 by a band filter 5. With this as a purpose, one among two sidebands generated in the output signal of the receiver 4 is suppressed by a proper amplitude adjustment of a driving signal in the phase modulator.