Terahertz Impulseimaging with Sparsearrays and Adaptive Reconstruction : Combination of Synthetic Aperture Focusing Technique, Coherence Factor & Interference Factor in Imaging Technology

Terahertz(THz) Impulse Imaging has many applications in security and nondestructive testing.Sparse THz arrays can dramatically reduce array complexity for imaging applications requiring a large field of view.Sparse arrays employing narrow band waves suffer from gratin lobe artifacts that severely degrade image quality.However,the short coherence length of single-cycle THz pulses provides an opportunity to overcome this limitation.Grating lobe artifacts can be suppressed with an adaptive weighting factor based on temporal coherence of signals from neighboring array elements.The spatial coherence of signals across the entire array can further improve image quality in adaptive manner .We experimentally demonstrate a 56*56 element 2d sparse array that adaptively suppresses grating lobe artifacts by 30db.The success of this adaptive processing relies on the single-cycle nature of the pulses employed in THz impulse imaging.