Electrostatic lens for cathode ray tubes

Claim 2

In a cathode ray tube, an electrostatic lens comprising: first and second terminal electrodes, spaced apart within the tube, means for applying the highest positive potential of potentials supplied to the lens to the terminal electrodes, said terminal electrodes shaped symmetrically around the axis of the tube, a center electrode disposed between the two terminal electrodes, means for applying a low potential which is lower than that applied to the terminal electrodes to said center electrode, said center electrode comprising two parts, and a correction electrode positioned between the two parts of the center electrode.

Claim 3

An electrostatic lens in accordance with claim 1 wherein the potential applied to said correction electrode is higher than that applied to said center electrode and substantially less than that applied to said terminal electrodes.

Claim 4

An electrostatic lens in accordance with claim 2 wherein all of said electrodes are formed of generally cylindrical sections, with the beam passing through the center thereof.

Claim 5

An electrostatic lens in accordance with claim 1 wherein, in combination as a main lens with a condenser lens for arrangement in a vidicon, the condenser lens located at the cathode side of the tube and the main lens located at the target side of the tube.

Claim 6

An electrostatic lens in accordance with claim 4 wherein the power of refraction of the main lens is at least as great as that of the condenser lens and wherein the distances of the main lens as from the target is at least as great as their respective focal lengths.

Claim 7

An electrostatic lens comprising: four electrodes formed of cylindrical sections, two of said electrodes constituting terminal electrodes spaced apart along a common axis for receiving the highest positive potential supplied to the lens applied thereto, a third, center electrode including two spaced apart sections for receiving a lower potential applied thereto, a fourth electrode, as a correction electrode, physically disposed between the two spaced apart sections of the center electrode for receiving a potential applied thereto which is higher than the level of the center electrode and lower than the level of said two terminal electrodes, and the third and fourth electrodes symmetrically arranged about the same common axis as that of said two terminal electrodes.

Claim 8

An electrostatic lens comprising: four electrodes formed of cylindrical sections, two of said electrodes constituting terminal electrodes spaced apart along a common axis for receiving the highest positive potential supplied to the lens applied thereto, a third, center electrode including two spaced apart sections for receiving a lower potential applied thereto, a fourth electrode, as a correction electrode, physically disposed between the two spaced apart sections of the center electrode for receiving a potential applied thereto which is higher than the level of the center electrode and lower than the level of said two terminal electrodes, and the third and fourth electrodes symmetrically arranged about the same common axis as that of said two terminal electrodes.

Claim 9

An electrostatic lens in accordance with claim 1 wherein the potential of said third, center electrode is negative.

Claim 10

An electrostatic lens in accordance with claim 7 wherein the potential of said fourth electrode as the correction electrode is in the order of 100 volts positive.