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(11) | EP 1 863 008 A3 |
(12) | EUROPEAN PATENT APPLICATION |
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(54) | Method and circuit for controlling the backlighting system of a display apparatus |
(57) In a display device images are reproduced by controlling the amount of light provided
by a light source by means of light modulators for individual pixels. Subsequent images
are synchronised to each other by synchronisation signals (VB) regularly occurring
at intervals corresponding to first time periods. The backlight is controlled to emit
light during fractions of second time periods or whole second time periods which are
equal to or shorter than first time periods. Several of the second time periods may
be nested and evenly distributed within the first time period. The signals for driving
the backlight are preferably generated in synchronism with the horizontal pixel clock.
Each of the fractions of second time periods or whole second time periods during which
light is emitted is divided into a number of elementary steps, wherein each elementary
step corresponds to a number of pixel clock periods. The number of elementary steps
is chosen according to the desired ratio of control of the backlight or contrast ratio,
e.g. 100 elementary steps for a contrast ratio of 1:100. During each of the second
time periods the backlight is controlled to be on for a number of elementary steps
corresponding to the desired contrast ratio.
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