The invention comprises a process for pre-aligning a lens with an optical system, the process comprising: providing a lens and an optical system having an optical axis, wherein the lens is apt to be aligned with the optical system to form on an image plane an image of a source object, the image having top, bottom, left and right edges; coarsely positioning the lens with respect to the optical system; and in a plane normal to the optical axis of the optical system, correcting the position of the lens until the values of four Combination Modulation Transfer Functions (C-MTF) are in predetermined ranges, the C-MTF being calculated at four coarse measurement locations situated close to the edges of the image along two coarse positioning axes crossing the center of the image, each for a combination pattern comprising a combination of a Sagittal pattern and a Tangential pattern.