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, the device comprising: an optical measuring head with a dual beam guide, the optical measuring head 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, the first measuring head configured to acquire and form a reflection spectrum of a first measuring beam directed towards a first measuring point located on the support and the second measuring head configured to acquire and form a reflection spectrum of a second measuring beam directed towards a second measuring point located on the edge region of the object; at least two spectral broadband light sources for producing light of the first measuring beam and the second measuring beam; a first optical fibre for coupling reflected light from the first measuring beam and a second optical fibre for coupling reflected light from the second measuring beam into different measurement inputs of a multi-channel measuring apparatus with at least two measurement inputs; a first light guide, a second light guide, a third light guide, and a fourth light guide; and a common spectrometer line positioned in the multi-channel measuring apparatus on which both the reflected light from the first measuring beam and the reflected light from the second measuring beam are directed and with which the reflection spectrum of the first measuring beam and the reflection spectrum of the second measuring beam are measured, the multi-channel measuring apparatus comprising at least one Y-coupler for each of the at least two measurement inputs of the multi-channel measuring apparatus, the first light guide coupled to a first spectral broadband light source of the at least two spectral broadband light sources and the second light guide coupled to a second spectral broadband light source of the at least two spectral broadband light sources, the first light guide and the third light guide connected to an input of a first Y-coupler of the at least one Y-coupler, each of the second light guide and the fourth light guide connected to an input of a second Y-coupler of the at least one Y-coupler, each of the third light guide and the fourth light guide routed to and secured by a holder on an input side of a spectrometer of the multi-channel measuring apparatus, the third light guide and the fourth light guide being offset in relation to one another in a spectral direction via the holder along a lengthwise direction of the spectrometer line on the input side of the spectrometer, characteristic curves of the reflection spectra differing from one another and the reflection spectra of the measuring heads differing from one another, distance peaks that are formed from the reflection spectra of the first measuring beam and the second measuring beam being evaluated as a measure of a difference in distance.