Patent ID: 8692981

Claim:
An evaluation device for path length measurement, configured to evaluate a measured signal which represents an intensity of a sequence of pulses of electromagnetic radiation, in particular of a sequence of light pulses, as a function of time after the sequence of pulses has covered a path length to be measured, the sequence of pulses having a repetition rate, the evaluation device being configured to determine a phase difference between a component of the measured signal, which component oscillates with a frequency, and a reference signal which oscillates with said frequency, said frequency corresponding to the repetition rate or a multiple of the repetition rate, and wherein the evaluation device is configured to generate, in order to determine the phase difference, a first signal and a second signal having another phase difference such that the first signal and the second signal each oscillates with another an other frequency which is different from said frequency, and that the other phase difference has a predetermined relation to said phase difference, the intensity of the sequence of pulses having harmonics, the harmonics having frequencies which are multiples of the repetition rate, the evaluation device being configured to respectively mix the component of the measured signal and the reference signal with a third oscillating signal to generate the first signal and the second signal by down-conversion, and the evaluation device being configured to generate the first signal and the second signal such that said other frequency at which the generated first signal and the generated second signal oscillate, less than the repetition rate.