Patent ID: 8818762

Claim:
A method for spatially resolved measurement of a physical variable, the method which comprises the following method steps: generating a first electrical signal with first time-varying frequency; generating a second electrical signal with a second time-varying frequency, which differs from the first frequency by a difference frequency; generating a third electrical signal with a third frequency, the third frequency corresponding to the difference frequency or a multiple of the difference frequency; generating an optical signal and modulating the optical signal by the first frequency; modifying the optical signal by an interaction with a test object to generate a modified optical signal, with a modification containing information relating the physical variable to be measured; converting the modified optical signal into at least one electrical signal, and thereby either: modulating the modified optical signal by the second frequency prior to converting; or mixing the modified optical signal with a signal modulated by the second frequency prior to converting; or mixing the at least one electrical signal with the second signal; digitizing the resulting mixed signal by sampling the mixed signal at the third frequency to form digitized data; and determining the physical variable in a spatially resolved fashion from the digitized data.