| 摘要 |
A device for spatially resolved measuring of a physical variable, comprising means for generating a first electrical signal (6) with a first frequency and a second electrical signal (7) with a second frequency, which differs from the first frequency by a difference frequency, an optical radiation source for generating an optical signal modulated by the first frequency, which optical signal can interact with a test object and be modified in the process, a mixer (11), which can mix an electrical signal (10) emerging from the optical signal with the second signal (7), a D/A converter (13) for digitizing the at least one mixed signal (12), and furthermore means, more particularly embodied as a DDS system (3), for generating a third electrical signal (8) with a third frequency, wherein the third frequency corresponds to the difference frequency or a multiple of the difference frequency, and wherein the D/A converter (13) can sample the mixed signal (12) at the third frequency in order to digitize it. |
