Time-reversal and model-based imaging in a THz waveguide

Malakeh A Musheinesh,Jeffrey A Fessler,Charles J Divin,Theodore B Norris

doi:10.1364/oe.17.013663

Abstract

We investigate two approaches to improving the resolution of time-reversal based THz imaging systems. First, we show that a substantial improvement in the reconstruction of time-reversed THz fields is achieved by increasing the system's numerical aperture via a waveguide technique adapted from ultrasound imaging. Second, a model-based reconstruction algorithm is developed as an alternative to time-reversal THz imaging and its performance is demonstrated for cases with and without a waveguide.

Highlights

There are several ways of approaching THz imaging including raster scanning and tomographic reconstruction [1]
An image point is reconstructed by first computing the time delays for a THz pulse to propagate from that point to every detector position
Each image point requires a different set of time delays and a different summation of the scattered signals

Summary

Introduction

There are several ways of approaching THz imaging including raster scanning and tomographic reconstruction [1]. We implemented a model-based reconstruction technique that uses the actual impulse response of the THz system and is better suited for reconstructing the object and eliminating spurious signals than the a priori time-reversal algorithm [5]. We demonstrate these methods for improved time-reversal imaging using a single emitter and a scanning single detector (i.e. in a form of synthetic-aperture imaging); the extension of these methods to multiple emitter and detector implementations is expected to be straightforward, and indicates a promising route to real-time THz imaging

Experimental System

Waveguide-enhanced time-reversal imaging

Model-based image reconstruction

Conclusion