– A flat part in which the temporal noise of the readout channel or the noise floor at 0 s exposure time, is dominant, in the example shown this noise is equal to 10 0.605 DN = 4.03 DN. Photon Transfer Curve : standard deviation versus effective output signal.įrom left to right, one can recognize three parts in this PTC graph : The obtained curve is shown in Figure 1.įigure 1. The standard deviation is representing the temporal noise of the pixels, the effective signal is equal to the average output signal minus the DC-offset of the output signal. The obtained measurement data/images can be used to create :ġ) Standard deviation versus average effective signal, both on a log-scale (“Mean-Standard Deviation”). S tot/ s tot = (S tot-S off)/( k 2 s R 2 + k(S tot – S off)) 0.5. The signal-to-noise ratio of the system under consideration can be written as : – s R : temporal noise associated with the readout channel, also the noise floor in dark at 0 s exposure time, – s tot : total temporal noise measured , – N o : number of optically generated electrons, While the measured temporal noise on pixel level can be written as : The measured signal of the sensor can be written as : For every exposure time applied, several images were grabbed, the average value of the obtained images as well as the temporal noise on pixel level was calculated. What was done to generate these images : the sensor under test was uniformly exposed to light, while varying the exposure time. So the same images (with light on the sensor) as used in the previous blogs are being re-used. In this blog, the application of the PTC on the data/images collected earlier will be described. The great advantage of this measuring method is the fact that no absolute measurements of any light input is needed. It was Jim who developed this wonderful technique in the ‘80s for CCDs, but the PTC is perfectly applicable to CMOS imagers as well. For those of you that are still hungry to get more information, please remember that Jim Janesick wrote a complete book about the PTC. The influence of many different sensor parameters on the PTC was studied and described. Over the last few years a lot of information about the Photon Transfer Curve (PTC) is being published in this blog.
0 kommentar(er)
