Circuit arrangement in a display device for avoiding geometrical distortions at the representation of texts, graphs and symbols

摘要

The invention relates to a circuit arrangement in a display device for avoiding geometrical distortions in the representation of texts, graphs and symbols on the video screen of a picture tube whose electron beam can be deflected row by row using at least two different frequencies by the horizontal deflection circuit and vertically using at least two different frequencies by a vertical deflection circuit, the vertical resolution of the information to be represented deviating from the maximum possible value prescribed by the row number in conjunction with a constant video screen format (4:3) and deflecting angle. In order to represent picture information in accordance with the FCC standard on a video screen according to the CCIR standard while avoiding geometrical distortions of the information content, it is provided that the switchable vertical oscillator is switched over to the corresponding frequency and synchronised by a switching signal as a function of the received vertical sync pulses, a second switching arrangement supplying control information for an electronic switch via which it is possible to switch on various further components in parallel or series with the component determining the amplitude of the vertical deflecting current, so that the vertical amplitude of the representation of a picture is amplified with a smaller number of rows than the maximum possible number in such a way that the picture area can also be completely written out in the vertical.