Browsing by Author "Spangenberg, Dirk-Mathys"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Investigation of a wool measurement device for determining the mean diameter of a sample consisting of multiple wool fibres
    (Stellenbosch : Stellenbosch University, 2012-03) Spangenberg, Dirk-Mathys; Perold, W. J.; Burger, A. J.; Von Bergmann, H.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: In the wool trade the mean diameter of wool is a primary indicator of wool quality. It is currently standard practice for a wool grower to send samples to a laboratory for classification before and after shearing. The devices used to make measurements on samples are often big and bulky and sensitive to the environment, thus they are not ideally suited for on site testing. A brief discussion of the industry is given with background information on existing devices as well as information about organic fibres in general. We test an experimental device which has the potential to be robust and compact based on the Fourier optical principle. Two initial designs are considered and the transmission design is further developed into a working system. The working system is evaluated in a sample measurement experiment. In our sample measurement experimentwe determine the mean diameter of a set of samples which has been analysed by an external testing body such that the measurements could be compared.
  • Thumbnail Image
    Item
    Time domain ptychography
    (Stellenbosch : Stellenbosch University, 2015-04) Spangenberg, Dirk-Mathys; Rohwer, Erich G.; Neethling, Pieter H.; Forbes, A.; Stellenbosch University. Faculty of Science. Dept. of Physics.
    ENGLISH ABSTRACT: In this work we investigate a new method to measure the electric field of ultrafast laser pulses by extending a known measurement technique, ptychography, in the spatial domain to the time domain which we call time domain ptychography. The technique requires the measurement of intensity spectra at different time delays of an unknown temporal object and a known probe pulse. We show for the first time by measurement and calculation that this technique can be applied with excellent results to recover both the amplitude and phase of a temporal object. This technique has several advantages, such as fast convergence, the resolution is limited by the usable measured spectral bandwidth and the recovered phase has no sign ambiguity. We then extend the technique to pulse characterization where the probe is derived form the temporal object by filtering meaning the probe pulse is also unknown, but the spectrum of the probe pulse must be the same as the spectrum of the temporal object before filtering. We modify the reconstruction algorithm, now called ptychographic iterative reconstruction algorithm for time domain pulses (PIRANA), in order to also reconstruct the probe and we show for the first time that temporal objects, a.k.a laser pulses, can be reconstructed with this new modality.