A model for Image Generation in Optronic (electro-optical) Sensor Systems (IGOSS) has been developed at the Defence Research Establishment in Sweden. The aim of this model is to study and evaluate different optronic sensor systems, and to use it as a tool in technical duel simulations. The model can operate on any input image, or on a sequence of images, and the user can see the resulting image after it has been processed by the different components in the system. It is also possible to use the model for calculations of the probability of detection as a function of distance for a target with a given size. To describe the performance characteristics of an electro-optical sensor system, IGOSS models the effects of vibrations, the optics, the detector, the processing unit, the display, the eye, and transversal movement of the sensor platform and/or a separate target in the background image. The performance characteristics is as far as possible described by modulation transfer functions (MTF) that are either calculated or read from a file. However, several effects are included in the model where MTFs can not be used. Example of these effects are: vignetting, sampling and a non-ideal fill factor of detector elements in the detector, detector generated noise, non- uniformity of the detector elements, and automatic gain control. The user can at run time decide what components or processes to use when the system is modeled. It is also possible to describe a particular component using different parameter values or type of transfer function.