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17 January 2005 The direction discrimination of single-mode VCSEL self-mixing laser Doppler velocimeters using automatic tracking triangular wave modulation
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Abstract
SM-LDV (Self-Mixing Type Laser Doppler Velocimeter) using single mode VCSEL (Vertical Cavity Surface Emitting Lasers) has many characteristic such as high accuracy of velocity measurement, low power dissipation and low cost. The saw-tooth waveform of Doppler signal can be used to discriminate the motion direction. Because of low light power of single mode VCSEL, the backscattered light is so weak that the saw-tooth waveform is not good enough to discriminate the motion direction. SM-LDV direction discrimination using single mode VCSEL modulated by triangular wave is not obviously dependent on the light power of Laser and its reliability is better. The dynamic range is very narrow when the VCSEL is modulated by constant frequency triangular wave. We present a method that VCSEL is modulated by triangular wave whose frequency is tracking the divided frequency of Doppler frequency shift (fD) and it can expand the dynamic range more than one order of magnitude. The results show that the dynamic range of direction discrimination can reach 5-500mm/s when the wavelength of single mode VCSEL is 850nm and the operating current is 8.6mA, the frequency of triangular wave is fD/16,the modulation current of triangular wave is 0.042mA.
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Deyong He, Jun Xu, Huaqiao Gui, Liang Lv, Tianpeng Zhao, Hai Ming, and Jianping Xie "The direction discrimination of single-mode VCSEL self-mixing laser Doppler velocimeters using automatic tracking triangular wave modulation", Proc. SPIE 5644, Optoelectronic Devices and Integration, (17 January 2005); https://doi.org/10.1117/12.573267
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