Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.662617
Title: Analogue VLSI for temporal frequency analysis of visual data
Author: Sutherland, Alasdair
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2003
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Abstract:
When viewed with an electronic imager, any variation in light intensity over time can provide valuable information regarding the nature of the object or light source causing the intensity change. By estimating the frequency of such light intensity variations, temporal frequencies can be extracted from the visual data, which may prove useful in a variety of applications. For instance, certain objects exhibit unique temporal frequencies, which could facilitate identification or classification. Other potential applications include remote, early failure detection for rotating machinery, as well as the possible detection of cancerous breasts using infra-red imaging techniques. The aim of the research reported in this thesis is the development of a CMOS image-processor, capable of extracting such temporal frequencies from any scene it is exposed to. In addition to finding the fundamental frequency, the sensor aims to extract the relative strength of up to the first four harmonics, performing a Fourier style decomposition of the incident light intensity into a temporal frequency signature. A heavy emphasis was placed on low power operation, leading to an investigation of analogue signal processing techniques with transistors biased in the subthreshold region of operation. The parallel processing advantages of combining light sensitive elements with signal processing elements in each pixel were also investigated, resulting in a system incorporating focal-plane computation. Software simulations of various novel system level algorithms are reported, with the successful approach used to create fundamental frequency maps of test data. The approach was also simulated to prove its robustness to noise commonly found in CMOS imager implementations. Circuits are presented which accurately extract the fundamental frequency of variations in light intensity, while benefiting from the low power consumption of subthreshold analogue circuitry. A novel algorithm which places a band pass filter onto the fundamental frequency of any incident light intensity with an accuracy of 3 % is also presented. The system can tune from 20 Hz to 10 kHz at a maximum rate of 9 kHz/s, and can be considered the first step in the creation of a single-chip pseudo-Fourier light intensity processing unit.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.662617  DOI: Not available
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