Menetelmä ja laite pinnan korkeustiedon määrittämiseksi pinnan tasomaisuuden mittauksessa

摘要

The invention concerns a method and arrangement for determining altitude data while measuring the evenness of a surface. A photograph of the surface is taken to form a video signal of the line picture type. From the video signal, phase information is detected for a carrier wave and the phase information is used to determine the [altitude?] data z. According to the invention, a phase- locked loop is used during the phase detection, in which a phase comparison is done. The momentary phase difference signals obtained from the phase comparisons are low-pass filtered to attenuate excessive phase alterations. For determination of the phase information, in addition to the momentary phase difference signals in the phase-locked loop 13, PLL, the method determines the absolute cumulative phase information φabs by determining the phase difference of each pixel in relation to the starting point S of the computation. IMAGE