Volume 629, September 2019
|Number of page(s)||15|
|Published online||02 September 2019|
The shape of the photon transfer curve of CCD sensors
LPNHE, (CNRS/IN2P3, Sorbonne Université, Paris Diderot), Laboratoire de Physique Nucléaire et de Hautes Énergies, 75005 Paris, France
2 Sorbonne Université, Paris Diderot, CNRS, IN2P3, Laboratoire de Physique Nucléaire et de Hautes Énergies, LPNHE, 75005 Paris, France
Accepted: 10 July 2019
The photon transfer curve (PTC) of a CCD depicts the variance of uniform images as a function of their average. It is now well established that the variance is not proportional to the average, as Poisson statistics would indicate, but rather flattens out at high flux. This “variance deficit”, related to the brighter-fatter effect, feeds correlations between nearby pixels that increase with flux, and decay with distance. We propose an analytical expression for the PTC shape, and for the dependence of correlations with intensity, and relate both to some more basic quantities related to the electrostatics of the sensor, which are commonly used to correct science images for the brighter-fatter effect. We derive electrostatic constraints from a large set of flat field images acquired with a CCD e2v 250, and eventually question the generally-admitted assumption that boundaries of CCD pixels shift by amounts proportional to the source charges. Our results show that the departure of flat field statistics from the Poisson law is entirely compatible with charge redistribution during the drift in the sensor.
Key words: instrumentation: detectors / methods: data analysis
© P. Astier et al. 2019
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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