Terahertz interferometric synthetic aperture tomography for confocal imaging systems

Abstract

Terahertz (THz) interferometric synthetic aperture tomography (TISAT) for confocal imaging within extended objects is demonstrated by combining attributes of synthetic aperture radar and optical coherence tomography. Algorithms recently devised for interferometric synthetic aperture microscopy are adapted to account for the diffraction-and defocusing-induced spatially varying THz beam width characteristic of narrow depth of focus, high-resolution confocal imaging. A frequency-swept two-dimensional TISAT confocal imaging instrument rapidly achieves in-focus, diffraction-limited resolution over a depth 12 times larger than the instrument's depth of focus in a manner that may be easily extended to three dimensions and greater depths.

Compressive sensing and adaptive sampling applied to millimeter wave inverse synthetic aperture imaging

“…Growing in popularity as the technology matures, millimeter wave (MMW) imaging techniques are increasingly attractive for non-destructive high-resolution imaging and radar applications such as through the wall imaging [13], concealed weapon detection [8,14,15], and foreign object detection [16,17]. High-resolution MMW imaging requires broad bandwidths [18] and large apertures [14].…”

“…Because of the unavailability of sensitive, low-cost detector arrays, MMW imaging relies heavily on synthesizing large apertures to acquire highresolution images. Synthetic aperture radar (SAR) and inverse synthetic aperture radar (ISAR) images are acquired by mechanically moving a single aperture [16,19] at the cost of slow acquisition speeds. Specifically, SAR images are formed by moving an aperture along a straight path and illuminating a stationary object, while ISAR images are either acquired by moving the aperture along a circular path around the target or by rotating the object in front of a fixed aperture.…”

Adaptive millimeter-wave synthetic aperture imaging for compressive sampling of sparse scenes

“…The impressive scans of obscured objects frequently reported in the MMW and THz literature are usually obtained through slow raster scanning of a source, object, or detector, often taking hours or days to complete [1][2][3]. Although source power and detector sensitivity are improving, the rate-limiting factor remains the desired signal-to-noise ratio (SNR) of the scattered signal coupled with the limited mechanical scanning speed and/or the associated mechanical settling time before an acquisition can begin.…”

“…The synthesized aperture can either use a diverging beam, as is typically done in synthetic aperture radar [3], or a quasi-optical system with a converging beam, as is done in optical coherence tomography (OCT) to increase penetration depth in scattering media [1,2], but the formalism is equivalent for both. The scanning time for synthetic aperture systems using classical processing techniques [e.g.…”

“…The scanning time for synthetic aperture systems using classical processing techniques [e.g. [1][2][3]] could be reduced if more powerful sources and more sensitive detectors were used, but that would greatly increase system cost. However, if the number of spatial samples could be reduced, it becomes more practical to use less expensive sources and detectors, especially if rapid mechanical scanning and efficient data processing are combined to reduce the time required to estimate a scene.…”