Apparatus for determining the distance between two plates (1, 2; 11, 12) that are largely arranged in parallel by interferometry, comprising a light source (3.1; 13.1), at least one beam splitter element (1.2; 11.2), at least one reflector element (2.2, 3.5, 3.6; 12.1, 12.2, 13.5), a plurality of deflection elements, a plurality of retroreflectors and a detection unit (4; 14), wherein the light source, the at least one beam splitter element, the at least one reflector element, the plurality of deflection elements, the plurality of reflectors and the detector unit are arranged in such a way that: - a beam emitted by the light source (3.1; 13.1) strikes a beam splitter element (1.2; 11.2) on the first plate (1; 11) in inclined fashion and said beam experiences a split there into a reflected reference beam and a transmitted measurement beam and - the measurement beam strikes a reflector element (2.2; 12.2) on the second plate and said measurement beam experiences a first return reflection there in the direction of the first plate and - the reference beam passes through a first deflection element and the measurement beam passes through a second deflection element, the reference and the measurement beam (R, M) subsequently each pass through an assigned retroreflector and, subsequently, the measurement beam passes through a third deflection element and the reference beam passes through a fourth deflection element, wherein both the first and second deflection element and also the third and fourth deflection element each exert different deflection effects on the reference and measurement beams (R, M) passing therethrough and - the reference beam then experiences a reflection at the first plate (1; 11) and - the measurement beam then experiences a second return reflection at a reflector element (2.2; 12.3) of the second plate (2; 12) such that: - the measurement beam and the reference beam then propagate collinearly in the direction of the detection unit (4; 14), where a plurality of phase-shifted distance signals (S0, S120, S240) are producible from the interfering measurement and reference beams (M, R). - a beam emitted by the light source (3.1; 13.1) strikes a beam splitter element (1.2; 11.2) on the first plate (1; 11) in inclined fashion and said beam experiences a split there into a reflected reference beam and a transmitted measurement beam and - the measurement beam strikes a reflector element (2.2; 12.2) on the second plate and said measurement beam experiences a first return reflection there in the direction of the first plate and - the reference beam passes through a first deflection element and the measurement beam passes through a second deflection element, the reference and the measurement beam (R, M) subsequently each pass through an assigned retroreflector and, subsequently, the measurement beam passes through a third deflection element and the reference beam passes through a fourth deflection element, wherein both the first and second deflection element and also the third and fourth deflection element each exert different deflection effects on the reference and measurement beams (R, M) passing therethrough and - the reference beam then experiences a reflection at the first plate (1; 11) and - the measurement beam then experiences a second return reflection at a reflector element (2.2; 12.3) of the second plate (2; 12) such that: - the measurement beam and the reference beam then propagate collinearly in the direction of the detection unit (4; 14), where a plurality of phase-shifted distance signals (S0, S120, S240) are producible from the interfering measurement and reference beams (M, R).