Process of analysis of the convergence of a cathode-ray tube with three ganged guns and a device forming a pick-up allowing implementation of this process

Process for analysis of the convergence of the three beams of a color cathode-ray tube with three ganged guns and shadow mask perforated with holes, preferably oblong, equipped with a deviator having horizontal and vertical deflection coilings, characterized by the fact that, for determining the projection of the convergence gaps between the three beams along at least one reference axis in a deviation direction preferably perpendicular to this reference axis, it consists of turning on only one of the three guns and applying a slowly variable signal to at least one of the deflection coilings and a scanning signal to at least the other deflection coiling so as to produce on the screen a luminous line moving slowly parallel to said reference axis, of measuring the light intensity through an analysis slit located parallel to the direction of the luminous line formed on the screen at the point where it is wished to determine the convergence characteristics, of fixing the values of the current in said coilings when the light intensity perceived through said slit is maximum, of repeating the same operations for the other two guns, and of calculating said projections of the convergence gaps according to said reference axis, knowing at least the three values of the aforementioned current and the deflection sensitivities of the cathode-ray tube in said area of the screen.