An optical measuring system for determining coordinates of points, more particularly for distance measurement, more particularly a geodetic surveying apparatus, coordinate measuring machine or scanning device, comprising • a radiation source (52,53,58) for emitting electromagnetic radiation having an emission wavelength (λ1,λ2,λ4,λLD,λLD1,λLD2), and • a receiving unit having □ a filter unit (51,57) for extracting electromagnetic radiation in a defined wavelength range according to the interference principle, and □ a detector (56,59) arranged in such a way that the radiation that can be extracted by means of the filter unit (51,57) is detectable by the detector (56,59), characterized in that the filter unit (51,57) comprises • at least two mirror elements (31a,31b) which are at least partly reflective and which are constructed in a multilayered fashion, wherein the mirror elements (31a,31b) are oriented substantially parallel to one another and two adjacent mirror elements (31a,31b) in each case enclose a cavity and are arranged at a specific distance with respect to one another, wherein the cavitiy is embodied as a an air gap or comprises a gaz, a liquid or an electroactive polymer as optically variable medium with a material refractive index and optical thickness is defined by a refractive index of the cavity and by the distance between the mirror elements (31a,31b), and • optical thickness varying means for varying the optical thickness, such that an extractable wavelength range of the filter unit (51,57) is varied, wherein the optical thickness varying means have actuating means for varying the position of the mirror elements (31a,31b) for varying the of the optical thickness by variation of the distance of the mirror elements (31a,31b) with respect to one another and/or refractive index adjusting means for varying the optical thickness by variation of the refractive index of the cavity, whereby the measuring system comprises a regulating unit, wherein the regulating unit interacts with the optical thickness varying means and the detector (56, 59) in such a way that the optical thickness is variable, in particular automatically, such that the emission wavelength (λ1,λ2,λ4,λLD,λLD1,λLD2) of the emitted radiation lies within the extractable wavelength range and the optical thickness is adjustable depending on a detection of the detector (56,59) and part of the electromagnetic radiation emitted by the radiation source (52,53,58) can be coupled out as reference beam by a beam coupling-out element and a reference wavelength is measurable by a sensor and the optical thickness is adjustable depending on the measured reference wavelength in such a way that the reference wavelength lies in the extracted wavelength range. • a radiation source (52,53,58) for emitting electromagnetic radiation having an emission wavelength (λ1,λ2,λ4,λLD,λLD1,λLD2), and • a receiving unit having □ a filter unit (51,57) for extracting electromagnetic radiation in a defined wavelength range according to the interference principle, and □ a detector (56,59) arranged in such a way that the radiation that can be extracted by means of the filter unit (51,57) is detectable by the detector (56,59), characterized in that the filter unit (51,57) comprises □ a filter unit (51,57) for extracting electromagnetic radiation in a defined wavelength range according to the interference principle, and □ a detector (56,59) arranged in such a way that the radiation that can be extracted by means of the filter unit (51,57) is detectable by the detector (56,59), • at least two mirror elements (31a,31b) which are at least partly reflective and which are constructed in a multilayered fashion, wherein the mirror elements (31a,31b) are oriented substantially parallel to one another and two adjacent mirror elements (31a,31b) in each case enclose a cavity and are arranged at a specific distance with respect to one another, wherein the cavitiy is embodied as a an air gap or comprises a gaz, a liquid or an electroactive polymer as optically variable medium with a material refractive index and optical thickness is defined by a refractive index of the cavity and by the distance between the mirror elements (31a,31b), and • optical thickness varying means for varying the optical thickness, such that an extractable wavelength range of the filter unit (51,57) is varied, wherein the optical thickness varying means have actuating means for varying the position of the mirror elements (31a,31b) for varying the of the optical thickness by variation of the distance of the mirror elements (31a,31b) with respect to one another and/or refractive index adjusting means for varying the optical thickness by variation of the refractive index of the cavity, whereby the measuring system comprises a regulating unit, wherein the regulating unit interacts with the optical thickness varying means and the detector (56, 59) in such a way that the optical thickness is variable, in particular automatically, such that the emission wavelength (λ1,λ2,λ4,λLD,λLD1,λLD2) of the emitted radiation lies within the extractable wavelength range and the optical thickness is adjustable depending on a detection of the detector (56,59) and part of the electromagnetic radiation emitted by the radiation source (52,53,58) can be coupled out as reference beam by a beam coupling-out element and a reference wavelength is measurable by a sensor and the optical thickness is adjustable depending on the measured reference wavelength in such a way that the reference wavelength lies in the extracted wavelength range.