Abstract
A method is described for automatic inspection of black matrix-screens of color picture tubes with in-line mask construction, because the dimensions of these matrix-screens are closely connected with the white uniformity of the tubes. A converged laser beam scans the inner surface of the picture tube panel using a scanning mirror located at the center of the panel curvature. Then, the beam transmits the panel and illuminates a photomultiplier through a diffuser set at the back of the panel. The widths of the matrix openings and black guard bands are obtained by measuring the corresponding scanning times in the wave-forms of the photomultiplier outputs. The measurements on 14-inch panels are reproducible with a standard deviation of 1 μm in about five seconds per panel with the prototype apparatus.
