Portland State University. Department of Physics
Date of Award
Master of Science (M.S.) in Physics
1 online resource (xi, 70 pages)
Charge coupled devices, Image processing -- Digital techniques
Digital imagers including Charge-Coupled Devices (CCD) are essential to most forms of modern photographic technologies. The quality of the data produced by digital imagers have made them an invaluable scientific measurement tool. Despite the numerous advantages of digital imagers, there are still factors that limit their performance. One such factor is the stability of the camera's gain, the ratio that dictates the imager's ability to convert incident photons to a measurable output voltage. Variations in gain can affect the linearity of the device and produce inaccurate measurements.
One of the factors that determines the gain of the camera is the sensitivity of the output amplifier. The purpose of this study is to compare the performance of two different output amplifier structures: the traditional source follower (SF) and the charge feedback amplifier (CFA). In studies of other solid state detectors, the CFA has shown a greater stability against variations in certain system parameters and environmental conditions such as operating temperature. It is thought that the CFA shows a superior stability over the SF, because the gain of the SF is dependent on multiple capacitances associated with the reset and output transistors, whereas the CFA gain is only dependent on its feedback capacitance. Furthermore, the CFA is able to handle a larger amount of charge than the SF, which increases the dynamic range of the output amplifier.
In this research, output amplifier stability is measured using gain and linearity data collected from a CCD manufactured with both types of amplifiers. Preliminary data is presented that indicates the CFA exhibits a greater linearity, larger dynamic range, and a more stable gain than the SF. Despite this the CFA suffers from a significantly larger level of noise. Suggestions for future research are also given as to how to verify and expand upon the results presented here.
Mylott, Elliot Eckman, "Improved Gain Stability of a Digital Imager Using a Charge Feedback Amplifier" (2015). Dissertations and Theses. Paper 2374.