22
Chapter 3
A CS Fourier terahertz imaging system
This chapter describes the first example of compressive sensing (CS) applied to THz
imaging. We demonstrate successful reconstruction of a target’s image with a ran-
domly chosen subset of the samples from the Fourier plane. We also combine CS
with traditional phase retrieval (PR) algorithms [67] for image reconstruction with
only a random subset of the Fourier amplitude image. Incorporation of CS into THz
imaging system designs can significantly reduce the image acquisition time.
3.1 Imaging setup
Our imaging system consists of a pulsed THz transmitter and receiver, both based
on photoconductive antennas, and two lenses, one of which approximately collimates
the THz beam while the other focuses the beam (see Figure 3.1). The object mask,
placed in between the two lenses, scatters the THz waves. The focusing lens forms
the Fourier transform of the object mask at its focal plane. The receiver, mounted on
a translation stage, performs a raster scan in the focal plane, over an area of 64 × 64
mm, at 1 mm intervals. A circular aperture (1 mm in diameter) is placed in front of
the receiver antenna so that it only samples a small area of the Fourier pattern, rather
than relying on the ~6 mm receiver aperture [68]. The object mask is made of opaque
copper tape on a transparent plastic plate. The object mask used in the experiments
in this chapter is an R-shaped hole, 34mm by height and 31mm by width.