Effects of vibration frequency and velocity parameters on Doppler frequency shift in laser Doppler vibrometer systems

Abstract

In this article, the effects of maximum velocity, vibration frequency and vibration amplitude parameters of objects on Doppler frequency shift (DFS) in Laser Doppler Vibrometer (LDV) systems using lasers at 1064 nm and 1550 nm wavelengths have been examined. In this context, while the velocity change of the object has been obtained in the range of 0 – 1200 µm/s with the laser at 1064 nm wavelength, the DFS varied between 0 and 2255.64 Hz. On the other hand, for 1550 nm wavelength, DFS have taken the values in the range of 0 – 1548.39 Hz. Moreover, for the 1064 nm wavelength, the maximum DFS and sampling time have been obtained in the range of 295.26 – 2066.84 Hz and 6.77 – 0.96 ms, respectively, in response to the change of vibration frequency from 50 to 350 Hz. For the same values of the vibration frequency, at the wavelength of 1550 nm, the maximum DFS and sampling time have changed in the range of 202.68 – 1418.78 Hz and 9.86 – 1.41 ms, respectively. Therefore, it is observed that as the vibration frequency increases, the maximum velocity and DFS increase linearly, while the sampling time decreases logarithmically. The results show that laser systems at 1064 nm wavelength respond faster but produce higher DFS values. On the other hand, LDV systems employing lasers at 1550 nm wavelength offer lower DFS and longer sampling times. Additionally, lasers that emit light at a wavelength of 1064 nm are more sensitive to velocity changes, whereas lasers at a wavelength of 1550 nm provide more stable measurement opportunities.