Investigations of resolution limits for indirect microwave holographic imaging

Abstract

This work describes how indirect holography which has previously been applied to the determination of antenna radiation patterns can be adapted for the imaging of passive objects. It provides details of how complex scattered field values can be obtained in a simple and inexpensive manner from sampled scalar intensity measurements taken over a single scanning aperture. This work uses indirect holographic techniques to image a number of simple objects including a rectangular metallic plate, a small metal plate covered by a dielectric sheet and a small metallic circular annulus. This work demonstrates that good quality images can be reconstructed from simple scalar intensity patterns. It demonstrates that clear outlines can be obtained in particular from reconstructed phase patterns and that good images can be obtained from objects with dimensions of the order of a half wavelength.

Indirect microwave holography and Through-Wall imaging

“…For applications where linear phase shift and sample spacing selections do not provide enough separation between the PWS components to achieve a proper component filtering due to an overlap, two solutions can be applied. One way to overcome this challenge is to decrease the sample spacing to increase the offset wave vector kr as given in (5) which would also result in an increase in the number of the sampling points required for the imaging. Therefore, this solution would increase the required total measurement and computational time.…”

“…Previous work on the use of indirect microwave holography was successfully demonstrated for the measurement of complex antenna near-field and far-field radiation patterns [2][3][4]. Recently, this technique has been extended to the inverse scattering problem and the imaging of metallic objects has successfully been demonstrated [5][6][7][8]. Indirect microwave holography differs from conventional microwave imaging techniques in that it does not require the direct measurement of the complex field but "indirectly" recovers it from intensity-only measurements performed using a low-cost scalar microwave power meter.…”

Early Stage Breast Cancer Detection Using Indirect Microwave Holography

“…This approach was originally developed for determining the complex aperture fields of antennas without using vector measurement equipment [20] and subsequently extended for imaging of metallic objects [21]. For the detection of metal objects, it was shown that the image can be reconstructed from amplitude measurements taken with a low-cost power meter.…”

Indirect Microwave Holographic Imaging of Concealed Ordnance for Airport Security Imaging Systems

“…In the literature, indirect microwave holography was proved to have a significant potential to be employed in the measurement of complex antenna near-field and far-field radiation patterns [12,13]. Recently, this technique has been extended to the imaging of early-stage breast cancer tumors [14] and unconcealed metallic objects [15]. Although promising results have been achieved in [14,15], the reconstruction of the original scattered field in these works was limited to the measurement plane.…”

“…Recently, this technique has been extended to the imaging of early-stage breast cancer tumors [14] and unconcealed metallic objects [15]. Although promising results have been achieved in [14,15], the reconstruction of the original scattered field in these works was limited to the measurement plane. This brings a significant challenge for the imaging of concealed objects, which requires the reconstruction of the scattered field at the object plane under the concealed medium to achieve optimum imaging response.…”