Abstract

Laser range-gated imaging systems can obtain images of targets hidden around the corner, with an intermediary reflective surface with certain specular reflection characteristics. This imaging mode is called non-line-of-sight imaging. This paper describes a simulation of the target signal illuminance and disturbance radiation on the photosensitive surface of a non-line-of-sight imaging system based on modeling of an intermediary reflective surface. Meanwhile, an image contrast model of a non-line-of-sight imaging system is constructed. Simulation of the image contrast for a laser range-gated imaging system as a non-line-of-sight imaging equipment was carried out by analyzing the effects of varying the target signal illuminance and intermediary reflective surface reflection. Our simulation results show that the reflection characteristics of the intermediary reflective surface have a significant effect on the non-line-of-sight imaging. Although ordinary active laser imaging can realize non-line-of-sight imaging for an intermediary reflective surface with significant specular reflection characteristics, a laser range-gated imaging system is indispensable for non-line-of-sight imaging with commonly used intermediary reflective surfaces without significant specular reflection characteristics. The image contrast model of non-line-of-sight imaging constructed in this paper provides insights into the theoretical analysis and system design, as well as practical application of non-line-of-sight imaging.

Highlights

  • Laser range-gated imaging can penetrate a strong scattering medium and capture the image of an object at a certain distance by applying active laser illumination, changing the gate delay time, and varying the gate width

  • This paper describes the construction of an image contrast model of non-line-of-sight imaging with a laser rangegated imaging system on the basis of the modeling of an intermediary reflective surface

  • The simulation results show that (1) the first-order backscattering is the dominant disturbance to non-line-of-sight images and can be effectively filtered out by laser range-gated imaging and (2) the effect of the third-order forward-scattering on non-line-of-sight images is often negligible since the third-order forward-scattering is insignificant compared to the target signal illuminance in most cases

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Summary

Introduction

Laser range-gated imaging can penetrate a strong scattering medium and capture the image of an object at a certain distance by applying active laser illumination, changing the gate delay time, and varying the gate width. Construction of an optical imaging model of the non-lineof-sight imaging process, which is based on the parameters of the intermediary reflective surface, the parameters of the laser range-gated imaging system, and the properties of the target, is vital for the theoretical analysis and system design of non-line-of-sight imaging based on laser range-gated imaging. This model assumes that the imaging will occur at night or in low-light conditions to reduce the impact of environmental illuminance

Image Contrast Model of Non-Line-of-Sight Imaging
Pulsed Laser and Range-Gated Imaging System
Reflection Characteristics of the Intermediary Reflective Surface
Illuminance on the target plane S2
Target signal illuminance on the photosensitive surface
Signal and noise under pulsed laser illumination
Apparent contrast of the image on a photosensitive surface
Analysis and discussion
Findings
Imaging Characteristic Analysis of Non-Line-of-Sight Imaging
Conclusions

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