U.S. Philips Corporation

Alfred Ketting

Edwin A Montie

Rudolf Kemner

Ronald Van Der Wilk

Petrus N Vis

Adriaan J Hoeven

A phosphor screen in a display device is scanned by separate electron beams in order to generate images of different frequency content in one color in substantially the same part of the phosphor screen. The different images can be perceived as a composite image for some time. The individual electron beams can be modulated by means of a cathode modulator on the basis of a high frequency and a low frequency component of an electronic image signal or on the basis of an image component and a text component of an electronic image signal. The modulations of the individual electron beams may be slightly delayed relative to one another in order to avoid overloading of the phosphor material.

CRT display device comprising a filter in the cathode modulator

A picture display device comprises an evacuated envelope and is provided at a first side with an electroluminescent display screen and at an opposite side with an electron gun (6). Between the electron gun (6) and the display screen, the device comprises deflection means with which an electron beam generated by the electron gun (6) can be deflected during operation. The electron gun (6) has at least an electron beam-generating portion (20) and is provided with a main lens system (40) having a first electrode (41), a final electrode (45) and at least one intermediate electrode (42-44) across which a main lens voltage is gradually applied step-wise during operation so as to form an electron-optical main focusing lens. The gun is further provided with means for presenting a dynamic potential (V.sub.d) to at least an electrode (41) of the main lens system (40), which is the first electrode viewed in the direction of propagation of the electron beam (7-9). For an increased dynamic focusing, a coupling capacitor (50) is arranged at least between said first electrode (41) and the subsequent electrode (42) of the main lens system (40).

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Eindhoven, Netherlands

Alfred Ketting