|dc.contributor.author||Nguyen, Krzysztof Quoc Khanh||en
|dc.description.abstract||This thesis describes work on a novel 3D imaging system that successfully implements
optical feedback and noise rejection mechanisms. The system is a combination of three
relatively new technologies, namely, holographic projection, Time of Flight (ToF) ranging
and Single Photon Avalanche Diode (SPAD) sensors.
Holographic projection is used to provide structured illumination with optical feedback
instead of more commonly used uniform illumination in similar imaging systems. It is
obtained using a Ferro-electric Liquid Crystal on Silicon Spatial Light Modulator (FLCoS
SLM). The structured illumination with optical feedback can be operated at up to 60 Hz with
the current device, and has been shown to provide an average gain of about 1.56 in useful
light levels. Alternatively, a gain over a limited area of up to a factor of 9 is possible with the
Time of Flight ranging is a method of choice for the system when depth estimation is
concerned. It works even at very low light levels and allows for sub-centimetre depth
resolution. ToF method was implemented using 20 MHz laser diode with 50 ps pulse
duration and 200 mW peak power, as well as a SPAD sensor. The SPAD sensor consisted of
a 32 32 array of 50 μm pixels, each with 10 bit Time to Digital Converter (TDC) with 50 ps
timing resolution. Sensor pixels feature 100 Hz mean Dark Count Rate (DCR).
The use of SPAD sensors with an adaptive sensing algorithm presented in this work has
been demonstrated to reduce effective noise levels as seen by the sensor by a factor of 16. As
a result, a significant gain in depth resolution can be achieved. The quantification of this gain
is explained in more detail within this work.
Furthermore, the work describes in detail system design, methodology of experimental
procedure as well as different algorithms essential to the correct operation of the system.
Significant amount of time is dedicated to diffraction pattern generation for the use in
holographic projection, as well as modelling of photon detection in SPAD sensors and
associated peak detection necessary to extract depth information from histograms of timed of
Moreover, the thesis discusses potential applications for the system based on the results
of system characterisation presented in this work. The current state of the system suggests
best suitability for gaming and machine vision applications.
Finally, the work offers potential solutions to the practical issues that remain unresolved
in the current system, alternatives for components used and paths for potential future
development of the system proposed.||en
|dc.contributor.sponsor||Engineering and Physical Sciences Research Council (EPSRC)||en
|dc.publisher||The University of Edinburgh||en
|dc.relation.hasversion||Automatic laser alignment for multifocal microscopy using a LCOS SLM and a 32×32 pixel CMOS SPAD array. D. Tyndall, R. Walker, K. Nguyen, R. Galland, J. Gao, I. Wang, M. Kloster, A. Delon and R. Henderson. 2011. Proc. SPIE 8086, Advanced Microscopy Techniques II.||en
|dc.relation.hasversion||An experimentally verified model for estimating the distance resolution capability of direct time of flight 3D optical imaging systems. K. Nguyen, E. M. D. Fisher, A. Walton and I. Underwood. 12, 2013, Measurement Science and Technology, Vol. 24, pp. 1-12.||en
|dc.relation.hasversion||Time of Flight Based 3D Image Sensing Using Holographically Projected Structured Illumination. K. Nguyen, D. Tyndall, R. Walker, R. Henderson, W. Hossack, I. Underwood, 1, 2012, SID Symposium Digest of Technical Papers, Vol. 43, pp 1151-4.||en
|dc.subject||Time of Flight||en
|dc.title||Characterisation of holographic projection as structured illumination in a Time-of-Flight based 3D imaging system||en
|dc.type||Thesis or Dissertation||en
|dc.type.qualificationname||PhD Doctor of Philosophy||en