The name is absent

31

Chapter 4

A Single-pixel CS terahertz imaging system

Most existing THz imaging systems, including the CS Fourier imaging system in
Chapter 3, use a raster-scan to move an object in front of a single pixel detector.
This mechanical scanning significantly limits the acquisition speed [2,48,51,52]. With
state-of-the-art technology, it takes about 6 minutes to scan a IOOmm × IOOrnm area
at 0.25mm resolution [2]. Real-time THz imaging has been demonstrated using focal-
plane detector arrays [3,4]. However, these systems tend to have higher complexity
and operational cost. For example, available array detectors, such as microbolome-
ter arrays, are relatively insensitive to THz radiation, so a bright THz source is
needed [3]. Single-shot electro-optic sensing also allows video-rate THz imaging [4],
but this method requires a large and costly amplified femtosecond laser system. One
implementation of the electro-optic imaging system can use a non-amplified laser
source [39], but, just like other typical pulsed THz systems, this system will not
have enough source power to image objects with high THz attentuation or at a long
distance. Even though interferometric or tomographic approaches have significantly
reduced the number of required measurements by, for example, non-uniform sampling
in the Fourier domain, the acquisition speed of such systems are still limited by raster
scanning unless a full detector array is used [5-7]. THz reciprocal imaging can achieve
high-speed imaging with a single-pixel detector but requires an unconventional source
array, with each source element modulated at a different frequency [71].

For practical, time-critical applications, a THz imaging system should not require

<<   46   47   48   49   50   51   52   >>

More intriguing information