Width measuring device

摘要

A width measuring device for measuring a width between first and second parallel edges of a track of a disk includes a video scanner for cross scanning the track within a predetermined area, and a sampling point detector for detecting crossing points between the edges of the track and a plurality of scanning lines. The number of occurrence of the sampled points are counted to provide distribution curves for the both side edges. Each distribution curve is divided into groups such that one group extends from one zero occurrence point to a next zero occurrence point with at least one peak point occurring between the two zero occurrence points. One dominant group is selected from each side, and an average point of the dominant group is defined as hypothetical centers. A valid region which expands a predetermined range from the hypothetical center is set for each side, and an average value of the valid region is calculated for each side. A width is obtained by calculating a distance between the average values for both sides.