Abstract: A system for determining at least one optical property of a lens system, comprising: a position sensitive detector 25 for generating image data representing an image projected onto the detector, and a controller 41 configured to receive the image data, to perform a first analysis of the image data in order to determine an identifier of a partial pattern contained in the image represented by the image data, to perform a second analysis of the image data in order to determine at least one property based on the image of the partial pattern, and to generate data representing the at least one optical property of the lens system associated with an image position of the image based on the determined at least one property.