Necessary and Sufficient Conditions for Best L1 Estimates of Ordinates of Convex Functions

An article of manufacture is disclosed for use in a projection television system. The article comprises a cathode ray picture tube having a funnel and a circular face panel with a rearwardly extending skirt and a window for receiving a cathodoluminescent imaging screen. The panel skirt is conjoinable with the funnel by mating along interfacing edges. The seal edge of the panel skirt defines a plane whose normal makes a non-zero acute cant angle with respect to the axis of the window. The funnel seal edge defines a plane whose normal makes a non-zero acute cant angle with respect to the funnel axis. The tube according to the invention is characterized by having a first pair of embossments on the funnel azimuthally spaced 180 degrees apart adjacent to seal edge of the funnel, and a second pair of embossments on the face panel skirt azimuthally spaced 180 degrees apart and adjacent to the seal edge of the skirt. The azimuthal position of the first and second pairs of embossment are predetermined such that the alignment of said pairs is effective to indicate the relative rotational position of the face panel and funnel and the predetermined tilt of the electron optical axis with respect to the projection optical axis.