The invention relates to an interferometer with a Schwarzschild objective, in particular for spectral interferometry for detecting distance, depth, profile, microprofile, shape, ripple and/or roughness of the optical path length in or on technical or biological objects, also in layer form, or an interferometer with a Schwarzschild objective for optical coherence tomography (OCT) and for the inspection of masks of semiconductor lithography in the EUV range by means of the phase shifting method. The interferometer comprises a source of electromagnetic radiation for illumination of the object, an object optical path and a reference optical path, and at least one measurement point in the object optical path, in which a surface or volume element of the object to be measured is at least approximately located. The interferometer comprises further a Schwarzschild objective with a convex primary mirror and a concave secondary mirror for illuminating and imaging at least one single object point of the object, and a detector for interferograms. A mirror surface, which is preferably a plane or concave surface, and assigned to a reference end reflector arranged in the reference optical path. The mirror surface is formed in the center region of the concave primary mirror of the Schwarzschild objective. Alternatively, a through-opening, to which a mirror below the primary mirror is assigned, is provided in the center region of the primary mirror and optionally reference end reflector is arranged downstream of said mirror. In a third configuration, in particular in case of Fizeau interferometer, the curvature of the at least one partially reflective splitter surface is such as to at least approximately correspond to the curvature of the wavefront impinging on the at least one partially reflective surface and forming a focus in the object space.