METHOD AND DEVICE FOR DETERMINING THE AMPLITUDE AND/OR PHASE OF A SELECTED FREQUENCY COMPONENT IN A DETECTED MEASUREMENT SIGNAL

The invention relates to a method and a computer unit for determining the amplitude and/or phase of a selected frequency component in a detected measurement signal, wherein an object is illuminated with light that is power-modulated according to a modulation signal having at least one frequency component, wherein a measurement signal is sampled with a sampling rate corresponding to at least four times the frequency of the selected frequency component, wherein each measurement value is multiplied by a value of a first and a second reference signal available at the respective measuring time in order to obtain a respective first and second product value for each measurement value, wherein the first reference signal has the selected frequency component and the second reference signal is phase-shifted by 90° relative to the first reference signal, wherein the first and the second product values are added up in order to obtain a first and a second product total value, from which the amplitude and/or the phase of the measurement signal are determined.