A position measuring apparatus for measuring the position of an object having an integrated optical circuit on a substrate comprising a first grating for diffracting a light beam into a reference bundle and a measuring bundle. The first grating couples the reference bundle to an input of a coupler and decouples the measuring bundle from the substrate. The measuring bundle is directed to a reflecting element on the object wherein the measuring bundle is reflected from the object. The coupler has means for inputting signals and for outputting signals wherein the input signals are brought into interference. A second grating couples the reflected measuring bundle to another input of the coupler. Detection means detect the outputs of the coupler and generate phase displaced signals representative of the outputs.