Generating high dynamic range images using a sky imager

One way to optimize their operation of Concentrated Solar Power (CSP) plants is to obtain accurate short-term forecasts of Direct Normal Irradiance (DNI). To do so, the use of sky imagers is developing. They should provide high-quality images, especially in the circumsolar area, where pixels are usually saturated. To reduce the saturated area around the Sun, High Dynamic Range (HDR) imaging is needed. This paper describes the steps required to obtain HDR images from a sequence of low dynamic range images acquired using a sky imager. Since the HDR image will be used to study the sky radiance and the circumsolar area, a particular care is taken to maintain a linear sensor's response throughout the process.