Beam penetration CRT with internal automatic constant deflection factor and pattern correction

A method for compensating variations of deflection sensitivity in a split anode beam penetration CRT as trace color is changed, comprising the steps of:

• directing an electron beam deflected in orthogonal principal axes through an expansion mesh and toward a faceplate;
• applying a fixed acceleration voltage to a funnel coating located between the faceplate and the expansion mesh;
• operating the CRT at a first trace color and with first and second deflection sensitivities in the respective principal axes of deflection by the steps of:
• operating the faceplate at the fixed acceleration voltage;
• operating a shielding electrode between the expansion mesh and the funnel coating at the fixed acceleration voltage;
• and
• creating from the expansion mesh to the shielding electrode and to the funnel coating an electric field having uniform curvature in each radial direction about the path of an undeflected electron beam;
• and
• operating the CRT at a second trace color and with unchanged first and second deflection sensitivities by the steps of:
• reducing the voltage applied to the faceplate;
• applying the reduced voltage of the faceplate to the shielding electrode;
• and
• reducing in each radial direction the curvature of the electric field between the expansion mesh and the funnel coating in accordance with the shape of the shielding electrode and the voltage difference from the expansion mesh to the shielding electrode, the reduction being greatest in those radial directions corresponding to the principal axes of deflection and less for the radial directions corresponding to the diagonals inbetween.