Abstract: A device for spatially resolved measuring of a physical variable has a device for generating a first electrical signal with a first frequency and a device for generating a second electrical signal with a second frequency. The second frequency differs from the first frequency by a difference frequency. An optical radiation source generates an optical signal modulated by the first frequency. The optical signal can interact with a test object and be modified in the process. A mixer can mix an electrical signal emerging from the optical signal with the second signal. A device, particularly embodied as a DDS system, generates a third electrical signal with a third frequency that corresponds to the difference frequency or a multiple of the difference frequency. A digital/analog converter digitizes the at least one mixed signal by sampling the mixed signal at the third frequency in order to digitize it.

Abstract: A device for spatially resolved measuring of a physical variable has a device for generating a first electrical signal with a first frequency and a device for generating a second electrical signal with a second frequency. The second frequency differs from the first frequency by a difference frequency. An optical radiation source generates an optical signal modulated by the first frequency. The optical signal can interact with a test object and be modified in the process. A mixer can mix an electrical signal emerging from the optical signal with the second signal. A device, particularly embodied as a DDS system, generates a third electrical signal with a third frequency that corresponds to the difference frequency or a multiple of the difference frequency. A digital/analog converter digitizes the at least one mixed signal by sampling the mixed signal at the third frequency in order to digitize it.