Abstract: A system which determines one or more properties of a lens includes a light source and a target pattern illuminated by the light source illuminates and substantially positioned at a first conjugate position of the lens. A detector, including an active surface, is positioned at a second conjugate position of the lens such that an image of the target pattern is formed on the active surface. The detector generates an analog electrical signal based on the image and the a generator converts the electrical signal to a representative digital signal for processing. In the system, the detector is movable relative to the lens to test the lens at plural focus positions, and plural detector output signals correspond to a feature of the target pattern at plural focus positions.