Optimized Design of Laser Vibration Measurement Transceiver Optical System for Applications with Rough Targets

Random scattering from a rough target surface causes a random phase distribution in the echo light field of a laser Doppler vibrometer (LDV), which in turn affects the interference between the echo light and the reference light. Based on related theories including Gaussian beam propagation and rough surface modeling, theoretical models for light field propagation, random target scattering, and interference intensity were established. Numerical simulation was conducted for a typical application scenario with a laser wavelength of 1550 nm, and a measurement distance of 1 m was used to investigate the effects of transceiver optical system parameters and wavefront aberrations on system performance. The results indicate that both the F-number of the transceiver lens and the wavefront aberrations have a significant impact on the average interference intensity. Under rough target conditions, to achieve a higher average interference intensity, the designed F-number of the transceiver lens should be approximately 70–85% of the F-number of the focusing lens. Regarding wavefront aberrations, defocus, 0∘ primary astigmatism, primary spherical aberration, and 0∘ secondary astigmatism have a more significant effect on the average interference intensity. For applications involving rough targets, the design tolerance values for the Zernike coefficients of these four aberrations are all higher than those for mirror-finished targets. For these four aberrations, the design tolerance values for ground surfaces are increased by 16.7–66.7%, while the design tolerance values for milled surfaces are increased by 11.1–66.7%, effectively reducing the difficulty of lens design. The results of this study provide a theoretical reference for the design of optical system parameters in LDV and other coherent detection systems.