19 February 2013 Dynamic capability of sensors with nonlinear pixels utilized by security cameras
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We have previously proposed a framework containing a typical security camera use case and have discussed how well this is handled by linear image sensors with various characteristics. The findings were visualized graphically, using a simple camera simulator generating images under well-defined conditions. In order to successfully render low-contrast objects together with large intra-scene variations in illuminance, the sensor requirements must include a high dynamic range combined with a comparably high signal-to-noise ratio. In this paper we reuse the framework and extend the discussion by including also sensors with non-linear pixel responses. The obvious benefit of a non-linear pixel is that it generally can cope with a higher scene dynamic range and that in most cases the exposure control can be relaxed. Known drawbacks are, for example, that the noise level can be fairly high. More specifically, the spatial noise levels are high due to variable pixel-to-pixel characteristics and lack of on-chip corrections, like correlated double sampling. In this paper we ignore the spatial noise, since some of the related issues have been addressed recently. Instead we focus on the temporal noise and dynamic resolution issues involved in non-linear imaging on a system level. Since the requirements are defined by our selected use case, and since we have defined a visual framework for analysis, it is straightforward to compare our findings with the results for linear image sensors. As in the previous paper, the image simulations are based on sensor data obtained from our own measurements.
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Anders Johannesson, Anders Johannesson, Henrik Eliasson, Henrik Eliasson, Sebastian Fors, Sebastian Fors, "Dynamic capability of sensors with nonlinear pixels utilized by security cameras", Proc. SPIE 8659, Sensors, Cameras, and Systems for Industrial and Scientific Applications XIV, 86590B (19 February 2013); doi: 10.1117/12.2000539; https://doi.org/10.1117/12.2000539

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