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COMPACT LASER DOPPLER VIBROMETER FOR SIMULTANEOUS MEASUREMENT OF MULTIPOINTS UTILIZING SELF-MIXING LASER DIODE WITH OPTICAL FIBER

利用光纤自混合激光二极管进行多点同步测量的紧凑型激光多普勒测振仪

基本信息

批准号：
05650386
负责人：
SHINOHARA Shigenobu
金额：
$ 1.34万
依托单位：
SHIZUOKA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

(1)Principle : The Doppler beat signal obtained from a self-mixing laser diode (SM-LD) has a sawtooth waveform when the emitted light beam is directly illuminated onto a vibrating loudspeaker surface. Every one wave in the beat signal corresponds to a half wavelength displacement (0.93 mum). Therefore, the digital surface displacement has been successfully counted by adding or subtracting a successive counting pulse train produced from the sharp edge of the each sawtooth in accordance with the positive or negative sign of the velocity, respectively, which is detected by a direction discrimination circuit.(2) Accuracy : The measured digital displacement amplitude, 10mum-140mum at 200Hz sinusoidal vibration, agreed well with the theoretical value within a few percent erro, when the sawtooth-like waveform is clear and sharp, however, the measured displacement was reduced to 40% - 90% of the theorelical value in accordance with the decrease of the sharpness of the sawtooth.(3) Measurable Range : The measurable range for vibration frequency and velocity was 7.6Hz-40kHz and 6.7mm/s-163mm/s, respectively. The measurable upper limit of displacement amplitude was 1200mum at 10Hz and 40mum at 500Hz, and the lower limit was around 4mum. In case of an SM-LD with an optical fiber the measurable range was greatly reduced, and the measured displacement was reduced to around 50% of the theoretical value, because the sharpness of the sawtooth was low.(4) Simultaneous Measurement : Two vibration waveforms at two different points on the loudspeaker were simultaneously measured using two SM-LD's with each optical fiber, and the phase difference between the two vibration waveforms was obtained by an FFT method.(5) Vibration Measurement of Rain-Drop Repelling Mirror : The displacement amplitude 0.6mum-0.8mum at a resonance frequency 42.97kHz could be measured using an SM-LD without an optical fiber, but could not in case of an SM-LD with a fiber.

（1）原则：从自混合半导体激光器（SM-LD）获得的多普勒拍频信号，当发射的光束直接照射到振动的扬声器表面上时，具有锯齿波波形。拍频信号中的每一个波对应于半波长位移（0.93 μ m）。因此，数字表面位移已经成功地通过根据速度的正或负符号分别从每个方向检测器的尖锐边缘加上或减去连续的计数脉冲串而被计数，该速度由方向识别电路检测。(2)准确度：在200 Hz正弦振动下，测量的数字位移幅值为10 μ m-140 μ m，与理论值在百分之几的误差范围内吻合，但当锯齿波清晰尖锐时，随着锯齿波尖锐度的降低，测量的位移幅值减小到理论值的40% - 90%。(3)可测量范围：振动频率和速度的可测量范围分别为7.6Hz-40 kHz和6.7mm/s-163 mm/s。位移幅值的可测上限为1200 μ m（10 Hz）和40 μ m（500 Hz），下限约为4 μ m。在具有光纤的SM-LD的情况下，可测量的范围大大减小，并且测量的位移减小到理论值的约50%，这是因为反射镜的锐度低。(4)同时测量：在扬声器上的两个不同的点处的两个振动波形同时使用两个SM-LD与每根光纤测量，并且通过FFT方法获得两个振动波形之间的相位差。(5)雨滴反射镜的振动测量：在共振频率42.97kHz下，用无光纤的半导体激光器可以测量0.6 μ m-0.8 μ m的位移，而用有光纤的半导体激光器则不能测量。