94-GHz Imager With Extended Depth of Field

Abstract

We describe a computational imaging technique to extend the depth-of-field of a 94-GHz imaging system. The technique uses a cubic phase element in the pupil plane of the system to render system operation relatively insensitive to object distance. However, the cubic phase element also introduces aberrations but, since these are fixed and known, we remove them using post-detection signal processing. We present experimental results that validate system performance and indicate a greater than four-fold increase in depth-of-field from 17" to greater than 68".Index Terms-Computational imaging, extended depth of field, millimeter wave imaging.

Passive millimeter-wave imaging with extended depth of field and sparse data

“…Over the past several years, imaging using millimeter wave (mmW) and terahertz technology has gained a lot of interest [1], [2], [3]. This interest is, in part, driven by the ability to penetrate poor weather and other obscurants such as clothes and polymers.…”

“…Recently, in [3], Mait et al presented a computational imaging method to extend the depth-of-field of a passive mmW imaging system. The method uses a cubic phase element in the pupil plane of the system to render system operation relatively insensitive to object distance.…”

“…The aberrations introduced by the cubic phase elements are then removed by post-detection signal processing. It was shown that, one can increase the depth-of-field of a 94GHz imager four times its normal depth-of-field [3].…”

“…One can model the 94-GHz imaging system as a linear, spatially incoherent, quasi-monochromatic system [3]. The intensity of the detected image can be represented as a convolution between the intensity of the image predicted by the geometrical optics with the system point spread function [12] ii(x, y) |i(x, y)…”

“…For a 94 GHz imager with an aperture diameter D = 24" and object distance do = 180", DoF ≈ 17.4" which ranges from 175.2" to 192.6" [3].…”