| 摘要 |
PURPOSE: To obtain a modulated-laser Doppler speedometer which can be miniaturized and whose application range is expanded by intensity-modulating a laser beam at a high frequency so as to be cast on a moving object and heterodyne-detecting reflected waves which have been returned and a reference signal. CONSTITUTION: A laser beam is intensity-modulated at a reference signal frequency (p) which is transmitted by an oscillator, and it is transmitted (an injection current is modulated by a semiconductor laser) so as to be cast on a target (a moving object). In reflected waves which has been returned, two Doppler frequency transitions are generated by the movement of the target with reference to the intensity-modulated laser beam. One is a Doppler frequency transitionΔωgenerated by the frequencyωof the laser itself (as a carrier), and the other is a Doppler frequency transitionΔp generated by a modulation signal (at a frequency (p)). Out of them, p+Δp is detected by a detector, a heterodyne detection is performed by a mixer between it and the reference signal (p), the frequency transitionΔp is detected, and the speed of the target is found.
|
