Optimisation of a Near-Field Scanning System.
Masters thesis, National University of Ireland Maynooth.
In this thesis, the optimisation of a near field scanning system is discussed. This
system, which consists of a stationary transmitter and a movable receiver, is in
use in the Experimental Physics Department at NUI Maynooth. The position of
the receiver is controlled by a two axis mechanical actuator.
The function of the near field scanning system is to characterise and verify
different optical components in the W-Band (75¡110 GHz). The measurements
are generally used as a comparison with optical set-ups that have been modelled
in commercial optical packages such as CST, GRASP and ZEEMAX.
Primarily this project is concerned with improving the overall efficiency of the
scanning system. At first the original set-up will be introduced along with the
reasoning behind subsequent upgrades. In Chapter 3 these upgrades to the
system will be outlined along with the problems that arose as a result. In particular,
a study of the mechanical vibration caused by the driving of the actuator is
discussed. This vibrational study is split into two parts; displacement analysis
and spectral analysis. Both methods are used in an attempt to understand the
source of these new excitations. The implications that these vibrations have on
the quality of measurements being made by the near field scanner will also be
Finally, the development of a new computational tool for alignment will be discussed.
The purpose behind this work is to develop a robust alignment tool that
will be the centrepiece of a standardised alignment method. The construction of
this tool along with its step by step testing will be outlined in Chapter 4.
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