Dissertation - FTP Directory Listing - University of Surrey

As can be seen the plot exhibits some non linearity, with 2 distinct gradients appearing the first inthe range of 2000-3500 DN gives a conversion gain of K = 0.178 DN/e- and the second gradient in therange 4000-7000 DN gives a conversion gain of K = 0.105 DN/e-. There is a large discrepancybetween these figures, it is unclear what has caused this effect but it could be due to a power supplyfault resulting in the pixels being reset to an incorrect voltage.LAS was then tested in Hard reset mode with the reset voltage set to 2.5V to see if the effect wasstill present.1200temp.var - dark.temp.var [DN]10008006004002000-2000 2000 4000 6000 8000 10000 12000 14000uy - uy. darkFigure 4.20 Photon transfer curve for hard reset operationFigure 4.20 shows the photon transfer curve for LAS when operating in hard reset mode, it can beseen there is still a slight nonlinearity but far less pronounced than for soft reset. The gradient givesa conversion factor of K = 0.177 DN/e- or 1/K = 5.65 e-/DN. There appear to be no anomalous pointsacross the range.Because of the non linearity seen in soft reset further tests were performed with LAS operating inhard reset. The next plot investigates the linearity response of the sensor shown in Figure 4.21.58