The influence of random vibrations on the performance of a dynamic phase-shifting speckle pattern interferometer is investigated by means of experiments and numerical simulations. Two aspects are evaluated: first, temporal unwrapping reliability, second, vibration-induced phase noise. The former is found to be a significant constraint, even for peak velocities well below the Nyquist velocity limit of the interferometer. Shorter sampling windows and higher framing rates are shown to increase the unwrapping success rate, but longer windows reduce the phase error. Three analytical criteria for determining the expected unwrapping success rate are proposed and compared.

We present what we believe to be a novel frequency scanning interferometry (FSI) system that integrates a passive Fabry–Pérot (FP) delay line to overcome bandwidth limitations in high-speed, long-range distance metrology. Unlike conventional FSI systems that require high acquisition rates or active switching mechanisms, this architecture utilizes the multiple optical delays within a single FP cavity to produce a comb of modulation frequencies, with a corresponding set of delay surfaces within the measurement volume. The target self-selects the delay surfaces with the lowest modulation frequencies, thus enabling range estimation with low-bandwidth detectors and low-throughput signal processing. Delay order ambiguity is resolved by means of a dual-cavity configuration. Using a swept VCSEL laser (100 kHz repetition rate, 100 nm bandwidth), we demonstrate absolute range measurements up to 1.4 m with sub-3 ppm precision. The maximum sampling rate is a factor of >67× lower than the 54 GS s ^-1 required by a conventional FSI system at this range and repetition rate, with a similar reduction in subsequent computational effort. The system is compatible with standard fiber components and scalable to high-speed, real-time metrology applications. It offers a cost-effective, compact solution for dynamic industrial environments where bandwidth, size, and power constraints typically limit FSI adoption.