Periodic aperture size measurement with submicron accuracy: application to nonuniform detection in color CRT shadow...

A novel periodic aperture size measurement optical system, which makes use of a coherent light beam/lens 2-D Fourier-transform property, is proposed. Measuring gain and errors is discussed. This optical system is able to produce aperture widths on a 3-D formed surface with the same accuracy as those on a flat surface and is well suited for measuring small aperture size variations in shadow masks for color TV tubes. These variations in shadow masks are considered to cause luminous and color nonuniformities and have been detected heretofore only by visual inspection. The minimum detectable size variation for this new measuring method is ~0.1 microm.