The invention relates to an arrangement and a method for measurement on a resonant oscillator with a mirror surface (8), which is displaced about an oscillation axis (2) with a period of duration (T), a laser diode (4) which emits a measuring beam (3) onto the first mirror surface (8), whereby a beam axis (21) of the measuring beam (3) intersects the oscillation axis (2). A photo receiver (6) is arranged opposing the first mirror surface (8) at a separation (a) from the beam axis (21) and a separation (b) from the mirror surface (8). The deflected measuring beam (5) moves within a quarter of a period (0 .... T/4) of an oscillation and over the photo-receiver (6) within a following quarter (T/4 .... T/2) of the period. The photo-receiver (6) is connected to an analytical circuit (11) which calculates the timepoints (t1, t2) from the impulses from the photo-receiver (6) and calculates a time period within the one half-wave (Δt = t2 - t1) from the above. The analytical circuit (11) calculates an actual value of the maximum amplitude with the equation:(I). The time duration Δt corresponds to a line dead time on writing sequential lines of a video image.