Disclosed is an optical system for measuring the topography of a test object, comprising a system for projecting an optically recognizable test pattern onto the surface of an object area that is to be measured, and an image-recording system and image-evaluation system for determining the parallactically displaced image coordinates of the test pattern in the object area that is to be measured, the distance of the centers of the aperture diaphragms of the projection system and the image-recording system forming a test basis. Said optical system is characterized in that the test pattern consists of a limited number of elements that are placed at regular intervals in at least one first axial direction, said axial direction being rotated by an angle a relative to the vertical projection of the test basis.