U.S. Philips Corporation

Hsien C Ou

Evert D Van Veldhuizen

Chi-Tien Chen

A first information (I) is displayed on a display screen of a display device (5). A vertical and horizontal position of a field of the first information (I) on the display screen is determined by a vertical start pulse (V) and by horizontal start pulses (H), both corresponding to or being extracted from the first information (I). The vertical position of a second information (Oi) on the display screen is determined by counting a certain number of the horizontal start pulses (H). To eliminate any remaining jitter, a time difference (Td) is determined between the active edge of the vertical start pulse (V) and that horizontal start pulse (H) which is nearest to the active edge of the vertical start pulse (V). If this time difference (Td) is smaller than a certain safe margin (Ni), the nearest horizontal start pulse (H) is so close to the active edge of the vertical start pulse (V), that an occurrence of vertical jitter is becoming likely. To avoid a dangerous vertical jitter situation, in a next field, the active edge of the vertical start pulse (V) is shifted in time over a shift period (Di), to obtain sufficient distance between the active edge of the vertical start pulse (V) and the nearest horizontal pulse (H).

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Taipei, Taiwan

Hsien C Ou