FPGA coarse-fine heterogeneous fusion dual femtosecond laser ranging for high-precision dynamic ambiguity-free measurement

To address the inherent trade-off between measurement range and precision as well as the limitations posed by ambiguity range in large-scale high-precision distance measurements, in this paper, we propose a dual femtosecond laser time-of-flight (ToF) sensor based on equivalent time-stretching and an FPGA-enabled coarse-fine fusion architecture. By employing a nonlinear asynchronous optical sampling (ACSOPS) strategy and cross-correlation peak extraction, femtosecond pulses delay is mapped from the femtosecond domain to the microsecond electronic domain, achieving a time-stretch ratio exceeding 10⁴. The proposed system integrates dual-comb nonlinear ACSOPS with traditional pulse ToF measurement, reducing data redundancy, alleviating timing jitter-induced errors and enabling sub - micron ranging precision with low - bandwidth detectors<b>.</b> A time-to-digital converter (TDC) core is implemented on the programmable logic (PL) side to perform millisecond-level coarse measurements over kilometer range. Concurrently, a femtosecond-level fine ranging algorithm based on cross-correlation peak phase extraction is executed on the processor system (PS) side. Real-time data fusion across the two domains is achieved via an AXI-Stream bus. And experimental results demonstrate that the proposed sensor achieves a root-mean-square (RMS) precision of less than 6 µm over a long range, effectively eliminating ambiguity in distance measurements. The system's high level of integration represents a significant step toward transitioning femtosecond-level ranging technology from laboratory research to industrial applications, providing what we believe to be a novel solution for high-precision distance measurements in dynamic industrial environments.