(19)
(11) EP 1 863 008 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
01.07.2009 Bulletin 2009/27

(43) Date of publication A2:
05.12.2007 Bulletin 2007/49

(21) Application number: 07108548.4

(22) Date of filing: 21.05.2007
(51) International Patent Classification (IPC): 
G09G 3/34(2006.01)
(84) Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC MT NL PL PT RO SE SI SK TR
Designated Extension States:
AL BA HR MK RS

(30) Priority: 02.06.2006 EP 06290910

(71) Applicant: Thomson Licensing
92100 Boulogne-Billancourt (FR)

(72) Inventors:
  • Ploquin, Didier
    38500 Parthenay de Bretagne (FR)
  • Machand, Philippe
    35500 Vitre (FR)
  • Morizot, GĂ©rard
    35500 Voiron (FR)

(74) Representative: Lindemann, Robert 
Deutsche Thomson OHG European Patent Operations Karl-Wiechert-Allee 74
30625 Hannover
30625 Hannover (DE)

   


(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.







Search report