Title:
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Full field laser doppler blood flow camera
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Laser Doppler Blood Flowmetry is a non-invasive technique that has been
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developed and used for measuring microvascular blood flow in tissue. The
technique utilises the backscattering of the laser light from moving red
blood cells and static tissue in order to extract information such as the
concentration and flow. This thesis describes the early stages of the
development of an integrated optical sensor array to perform full field laser
Doppler blood flow imaging. This technique will eliminate the need for
mechanical scanning and the data bottleneck that exists between the
photodiode array and processing unit, so allowing the direct measurement
ofblood flow maps to be obtained in real time.
A single channel laser Doppler blood flowmetry device has been
implemented using a photodetector linked to a field programmable gate
array. Filters (low pass, band pass and frequency weighted) have been
developed for processing the Doppler signals to obtain flow and
concentration measurements. The responses of these filters are
demonstrated using measurements from modulated light signals, a rotating
diffusing disc and in vivo measurements of blood flow. Several types of a
linear array system and current to voltage converter are considered for the
first fabrication run of the project based on the cost of fabrication and
performance of the system such as operating frequency, gain, bandwidth
and signal to noise ratio. A 16x1 linear array of photodiodes is developed
and integrated on the same chip with the laser Doppler processing design, successfully implemented in the single channel laser Doppler system, using
the standard 0.35Jlm CMOS technology. The characterisation of each
individual part of the design was carried out and compared with the
Cadence simulation results. The performance of the system on a single
pixel is also evaluated using a modulated laser as a light source. The
knowledge gained from the characterisation and the overall performance of
the linear array system is then used to develop a full field laser Doppler blood flow camera.
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