A Novel Signal Processing Strategy for Short-Range Laser Feedback Interferometry Sensors

TL;DR

This paper introduces a new signal processing method for short-range laser feedback sensors, enabling high-precision distance and velocity measurements at very close ranges with improved ambiguity resolution and robustness.

Contribution

It presents a novel four-ramp modulation scheme that resolves beat frequency ambiguities and spectral blind spots in compact laser feedback sensors.

Findings

Achieves reliable measurements at distances as low as 1 cm

Resolves spectral blind regions caused by hardware limitations

Demonstrates robust, low-noise performance with state-of-the-art hardware

Abstract

The rapid evolution of wearable technologies, such as AR glasses, demands compact, energy-efficient sensors capable of high-precision measurements in dynamic environments. Traditional Frequency-Modulated Continuous Wave (FMCW) Laser Feedback Interferometry (LFI) sensors, while promising, falter in applications that feature small distances, high velocities, shallow modulation, and low-power constraints. We propose a novel sensor-processing pipeline that reliably extracts distance and velocity measurements at distances as low as 1 cm. As a core contribution, we introduce a four-ramp modulation scheme that resolves persistent ambiguities in beat frequency signs and overcomes spectral blind regions caused by hardware limitations. Based on measurements of the implemented pipeline, a noise model is defined to evaluate its performance and sensitivity to several algorithmic and working point parameters. We show that the pipeline generally achieves robust and low-noise measurements using state-of-the-art hardware.