  Recently, we introduced a Portable HAndheld Spectral Reflection (PHASR)
Scanner to allow THz Time-Domain Spectroscopic (THz-TDS) imaging in clinical
and industrial settings using a fiber-coupled and alignment-free telecentric
beam steering design. The key limitations of the version 1.0 of the PHASR
Scanner were its field-of-view and speed of time-domain trace acquisition. In
this paper, we address these limitations by introducing a heliostat geometry
for beam scanning to achieve an extended field-of-view, and by reconfiguring
the ASynchronous OPtical Sampling (ASOPS) system to perform Electronically
Controlled OPtical Sampling (ECOPS) measurements. The former change improved
the deflection range of the beam, while also drastically reducing the coupling
of the two scanning axes, the combination of which resulted in a larger than
four-fold increase in the FOV area. The latter change significantly improves
the acquisition speed and frequency domain performance simultaneously by
improving measurement efficiency. To accomplish this, we characterized the
non-linear time-axis sampling behavior of the electro-mechanical system in the
ECOPS mode. We proposed methods to model and correct the non-linear time-axis
distortions and tested the performance of the high-speed ECOPS trace
acquisition. Therefore, here we introduce the PHASR Scanner version 2.0, which
is capable of imaging a 40$\times$27 mm$^2$ FOV with 2000 traces per second
over a 100 picosecond TDS range. This new scanner represents a significant leap
towards translating the THz-TDS technology from the lab bench to the bedside
for real-time clinical imaging applications.
