Optimisation of a Near-Field Scanning System

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 outlined. 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