Patent ID: 6844665
Filing Date: 2005-01-18
Classification: H01J

Abstract:
1. A display device comprising a cathode ray tube, a deflection unit and display screen, the cathode ray tube including an in-line electron gun comprising: a main lens portion for generating a main lens field; a pre-focusing lens portion which, viewed in the direction of travel of electron beams, comprises a first, a second and a third electrode for generating a pre-focusing lens field, wherein the first, second and third electrodes are provided with apertures for transmitting the electron beams, and the deflection unit is arranged to deflect the electron beams across the display screen; wherein the electron gun comprises means for generating an auxiliary lens field between the pre-focusing lens field and the main lens field such that the intensity of the auxiliary lens field causes the electron beams to leave the main lens field substantially parallel to the in-line plane, and such that the diameter of the electron beams past the anode side of the main lens field is smaller than or substantially equal to the diameter of an aperture of the second electrode throughout the deflection of the electron beams across the display screen, wherein the means for generating an auxiliary lens field are adapted to generate an astigmatic lens field in the main lens portion such that the intensity at the astigmatic lens field in the direction perpendicular to the in-line plane is stronger than the intensity of the astigmatic lens field in the in-line plane, and wherein in the direction of travel of the electron beams, the inline electron gun further comprises a fourth electrode, a fifth electrode a sixth electrode, and a seventh electrode, which electrodes have apertures for transmitting electron beams, and in that the display device comprises means for applying a grid voltage to the second and fourth electrode and a focus voltage to the third and fifth electrodes.