Apparatus for measuring dimensional deviations

Claim 1

Apparatus for gauging the distance between two parallel edges present in a moving web, comprising means for moving the web along a generally predetermined path, a radiant energy source directing radiation towards such path, two groups of radiation responsive detectors for receiving radiation after transmission or reflection by said web, each said group comprising a plurality of discrete detectors having their radiation responsive areas arranged in a row extending generally normal to one of said edges and adapted to be intersected by said edge on movement of the web and means for reading out the number of detectors in both groups which receive radiation after transmission through or reflection by said web to give an indication of said distance, said readout means comprising a matrix of light-producing elements arranged in intersecting rows and columns with one such element at each intersection, trigger means associated with each detector of said groups for selecting those detectors receiving a quantity of radiation varying from a given threshold value, the trigger means for the detectors in one group having the outputs thereof connected to one side of the terminals of said light-producing elements in the corresponding columns of said matrix, and the trigger means for the detectors in the other group having the outputs thereof connected to the other side of the terminals of said light-producing elements in the corresponding rows of said matrix.