A single-exposure technique to extend the dynamic range of vision sensors is presented. It is particularly suitable for vision algorithms requiring region-of-interest (ROI) tracking under varying illumination conditions. The operation is supported by two intertwined photodiodes at pixel level and two digital registers at the periphery of the pixel matrix. These registers divide the focal plane into independent regions within which automatic concurrent adjustment of the integration time takes place for each frame. At pixel level, one of the photodiodes senses the pixel value itself, whereas the other, in collaboration with its counterparts in every prescribed ROI, senses the mean illumination of that specific ROI. An additional circuitry interconnecting both photodiodes asynchronously determines the integration period for each ROI according to its mean illumination. The experimental results for a quarter video graphics array prototype CMOS vision sensor are reported.Introduction: The most usual technique for imagers to deal with scenes featuring high dynamic range (HDR) consists in taking multiple captures per frame with different exposure periods and subsequently combining them [1]. Although this technique performs well for still images, it creates artefacts if motion occurs during multi-exposure. Specialised sensing architectures capable of extending the dynamic range through single exposure [2-4] are thus highly demanded at present [5]. This is also the case for vision sensors that, unlike imagers, are intended not to simply provide high-quality images but to support the automatic extraction of meaningful information from the activity, i.e. motion, taking place in a scene. Despite this fundamental difference between the targeted functionality of imagers and vision sensors, the latter commonly makes use of the HDR techniques devised for the former. The development of specific HDR techniques tailored for the requirements of vision algorithms has received little attention. In this Letter, we describe a sensing architecture particularly suitable for one of the basic tasks implemented by vision algorithms: region-of-interest (ROI) tracking. Once a certain ROI is spotted, a vision algorithm typically tracks it across the scene while carrying out the prescribed analytics. This tracking and the corresponding analytics must not be affected by variations in the illumination over the ROI. Indeed, the priority should be to adapt the capture for that ROI while ensuring that new ROIs can still be detected and adapted in case they enter the scene. This is exactly the functionality provided by the proposed architecture.