Imaging through fog using quadrature lock-in discrimination

TL;DR

This paper demonstrates a novel imaging technique using quadrature lock-in detection that significantly improves visibility through fog, enabling better detection of distant beacons and obscured objects in poor visibility conditions.

Contribution

The study introduces a field-tested method combining intensity modulation and software-based lock-in detection to enhance imaging contrast in foggy environments.

Findings

Enhanced contrast-to-noise ratio in foggy conditions

Successful imaging of beacons over hectometric distances

Revealed obscured objects using modulated illumination

Abstract

We report experiments conducted in the field in the presence of fog, that were aimed at imaging under poor visibility. By means of intensity modulation at the source and two-dimensional quadrature lock-in detection by software at the receiver, a significant enhancement of the contrast-to-noise ratio was achieved in the imaging of beacons over hectometric distances. Further by illuminating the field of view with a modulated source, the technique helped reveal objects that were earlier obscured due to multiple scattering of light. This method, thus, holds promise of aiding in various forms of navigation under poor visibility due to fog.