60
pixel. The smaller each SLM pixel is, the more the signal detection is prone to noise
corruption. If either the THz source power or the detector sensitivity is too low, the
signal-to-noise (SNR) performance of the system goes down. One trivial solution is
to obtain more signal averages to increase the SNR, but the image acquistion time
also increases proportionally. Using a lock-in amplifier can significantly eliminates
system noise, but only works for amplitude measurements at a single time delay or
is otherwise slow in the long scan mode. The best solution is to operate the CS
imaging system with a high-power continuous-wave THz source, such as quantum
cascade lasers, tuned at the resonant frequency of the THz SLM and with a highly
sensitive single-point detector such as a Golay cell. Figure 6.1 qualitatively compares
the source power and receiver requirements, and the speed performance of various
imaging systems. The table assumes all imaging systems implementation with a
continuous-wave THz source. If a pulsed THz source is used, the recently published
electro-optic imaging technique using a time-of-flight demodulation detector array
may be the least costly solution for fast imaging [39]. However, the power limitation
in all pulsed THz sources is still a challenge to practical imaging. Alternatively, a
tunable continuous-wave source may provide enough power for the single-pixel CS
imaging system if hyperspectral information is desired. More research effort is still
required to build a practical CS imaging system with continuous-wave THz systems
and to compare its performance with the pulsed THz system used in this thesis.
More importantly, in order for this CS imaging scheme to have comparable per-
formance to imaging using a microbolometer array, the single-pixel THz detector
needs to have a dynamic range y times the dynamic range of a single element in the
detector array, where N is the number of image pixels [10]. If a single-pixel THz de-
tector can achieve this desirable dynamic range with better signal sensitivity, the CS
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