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- All Subjects: Imaging
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
Description
The detection and characterization of transients in signals is important in many wide-ranging applications from computer vision to audio processing. Edge detection on images is typically realized using small, local, discrete convolution kernels, but this is not possible when samples are measured directly in the frequency domain. The concentration factor edge detection method was therefore developed to realize an edge detector directly from spectral data. This thesis explores the possibilities of detecting edges from the phase of the spectral data, that is, without the magnitude of the sampled spectral data. Prior work has demonstrated that the spectral phase contains particularly important information about underlying features in a signal. Furthermore, the concentration factor method yields some insight into the detection of edges in spectral phase data. An iterative design approach was taken to realize an edge detector using only the spectral phase data, also allowing for the design of an edge detector when phase data are intermittent or corrupted. Problem formulations showing the power of the design approach are given throughout. A post-processing scheme relying on the difference of multiple edge approximations yields a strong edge detector which is shown to be resilient under noisy, intermittent phase data. Lastly, a thresholding technique is applied to give an explicit enhanced edge detector ready to be used. Examples throughout are demonstrate both on signals and images.
ContributorsReynolds, Alexander Bryce (Author) / Gelb, Anne (Thesis director) / Cochran, Douglas (Committee member) / Viswanathan, Adityavikram (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Imaging using electric fields could provide a cheaper, safer, and easier alternative to the standard methods used for imaging. The viability of electric field imaging at very low frequencies using D-dot sensors has already been investigated and proven. The new goal is to determine if imaging is viable at high frequencies. In order to accomplish this, the operational amplifiers used in the very low frequency imaging test set up must be replaced with ones that have higher bandwidth. The trade-off of using these amplifiers is that they have a typical higher input leakage current on the order of 100 compared to the standard. Using a modified circuit design technique that reduces input leakage current of the operational amplifiers used in the imaging test setup, a printed circuit board with D-dot sensors is fabricated to identify the frequency limitations of electric field imaging. Data is collected at both low and high frequencies as well as low peak voltage. The data is then analyzed to determine the range in intensity of electric field and frequency that this circuit low-leakage design can accurately detect a signal. Data is also collected using another printed circuit board that uses the standard circuit design technique. The data taken from the different boards is compared to identify if the modified circuit design technique allows for higher sensitivity imaging. In conclusion, this research supports that using low-leakage design techniques can allow for signal detection comparable to that of the standard circuit design. The low-leakage design allowed for sensitivity within a factor two to that of the standard design. Although testing at higher frequencies was limited, signal detection for the low-leakage design was reliable up until 97 kHz, but further experimentation is needed to determine the upper frequency limits.
ContributorsLin, Richard (Co-author) / Angell, Tyler (Co-author) / Allee, David (Thesis director) / Chung, Hugh (Committee member) / Electrical Engineering Program (Contributor) / W. P. Carey School of Business (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12