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Development of a system for controlling a terahertz time domain spectroscope and analyzing its performance characteristics

 
: Villar Corrales, Angel
: Stumm, Christopher

:
Volltext urn:nbn:de:0011-n-5070834 (9.6 MByte PDF)
MD5 Fingerprint: 2f17cf3c1104eb3229490ac4fc755854
Erstellt am: 6.9.2018


Saarbrücken, 2018, V, 64 S.
Saarbrücken, Hochschule für Technik und Wirtschaft des Saarlandes, Bachelor Thesis, 2018
Englisch
Bachelor Thesis, Elektronische Publikation
Fraunhofer IZFP ()
THz spectroscopy; Modular Measurement System (MMS)

Abstract
Within the scope of this work, a software used to carry out THz Spectroscopy has been implemented. This program, combined with the appropriate THz Spectroscope, allows a user to carryout Nondestructive Evaluation (NDE) over a wide range of materials. This software consist of three different modules that have been integrate into the Modular Measurement System (MMS) of Fraunhofer IZFP. This is a LabView architecture simplifes computer-aided measurements by allowing the separation of a complex software into simpler modules which perform different tasks. Furthermore, efficient LabView programming technique shave been used to make the program scalable and modular. The Scanner Module controls two servo motors used to move the sample, so different points and areas can be measured. The THz Modules carries out the THz Spectroscopy by opening a connection with the spectroscope, calibrating the hardware and making the corresponding measurements. Finally, the Scan Inspector Module displays the data and allows a user to process and analyze it. These three modules have been combined with the already implemented MMS Main Program, which calls the MMS Modules in the correct order, and the 4D Scan Controller, which allows the user to select the dimensions that will be measured and returns the two-dimensional coordinates. Three different measurement types have also been implemented. The Step by Step Mode measures every pixel with one THz Spectroscopy pulse and displays it at the moment; the Average Method measures every pixel a number of times that the user desires and averages the waveforms, also displaying the received data at the moment. Finally, the Line Scan Mode measures in vector form rows/columns without stop, thus increasing the measurement speed, and displays the whole vector once the row/column is completely measured. The results obtained with the different measurement methods were quite satisfying. Line ScanMode carried out quite fast measurements with an acceptable accuracy, whereas Spectroscopy with the Normal Mode provided really clear and precise measurements, although they took quite long time. Furthermore, the coordinates given to the Controller were applied with exact precision, and the processing carried out by the Scan Inspector responded accordingly to the specifcations. Not only the software was tested, but also some performance characteristics of the Hardware has been analyzed. Specifically, the optimal measuring distance of the THz Spectroscope has been studied both in transmission and reflection. The analysis has been carried out with the same concept in all cases. A small are of a sample was measured for several distances, the data recorded was run with a python script that calculated, processed and plotted it in order to know at which distance the obtained results are optimal. After having extensively analyzed the results, it was learned that the the THz Spectroscope should be turned on some time (around 3 hours) before the beginning of the measurements for the temperature to become constant, so it does not affect the recorded results. Finally, as long as the temperature remains constant, it has been obtained that the distance does not affect measurements carried out in transmission, whereas the optimal distance in reflection is around 21-22 mm as, at these distances, the measurements are successfully captured with their maximal amplitude.

: http://publica.fraunhofer.de/dokumente/N-507083.html