1. An optical measuring device for acquiring differences in distance, in particular for acquiring in situ a stage height between a support and an edge region of an object, comprising: an optical measuring head with dual beam guide which is configured as a dual measuring head having a first measuring head and a second measuring head, a measuring head guide device in which the first measuring head and the second measuring head are positioned side by side and connected mechanically, at least one spectral broadband light source for producing light of a first measuring beam and a second measuring beam, wherein the first measuring head directs the first measuring beam towards a first measuring point located on a support, and the second measuring head directs the second measuring beam towards a second measuring point located on an edge region of the object; means positioned in the first measuring head and the second measuring head of acquiring and forming reflection spectra of the first measuring beam directed towards the first measuring point and reflection spectra of the second measuring beam directed towards the second measuring point, a first optical fibre for coupling the reflected light from the first measuring beam and a second optical fibre for coupling the reflected light from the second measuring beam into different measurement inputs of a multi-channel measuring apparatus with a plurality of measurement inputs, a spectrometer line positioned in the multi-channel measuring apparatus with which the reflection spectra of the first measuring beam and the reflection spectra of the second measuring beam can be measured, and an evaluation unit connected via a sensor line to the spectrometer line with which distance peaks can be formed from the reflection spectra of the first measuring beam and the second measuring beam measured by the spectrometer line and the distance peaks can be evaluated as a measure of a difference in distance.