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Method and circuit for controlling the backlighting system of a display apparatus

A display device and circuit technology, applied to static indicators, instruments, etc., can solve problems such as PLL circuit function and stability problems, and achieve the effect of avoiding possible changes

Inactive Publication Date: 2007-12-05
THOMSON LICENSING SA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Typically, such PLL circuits with low frequency locked loops suffer from functionality and stability issues

Method used

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  • Method and circuit for controlling the backlighting system of a display apparatus
  • Method and circuit for controlling the backlighting system of a display apparatus
  • Method and circuit for controlling the backlighting system of a display apparatus

Examples

Experimental program
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Embodiment Construction

[0026] 1 and 3 have been described above and will not be described in detail.

[0027] Fig. 4 shows an example circuit for performing one embodiment of the inventive method, which uses the pixel clock PC and the vertical or frame sync signal VB to generate the control signal BLC for the backlight. The pixel clock PC is provided to the first counter 201 at the clock input terminal of the first counter 201 . The number PPS of pixel clock periods per basic step is supplied to the first counter 201 at the data input. A vertical or frame sync signal VB is supplied to the load input of the first counter 201 . The output of the first counter 201 is applied to the clock inputs of the second counter 202 and the third counter 203 . The number SPP of elementary steps per subcycle is supplied to the data input of the second counter 202 . A vertical or frame sync signal VB is also provided to the load input of the second counter 202 . The output of the second counter 202 and the vertic...

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PUM

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Abstract

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 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.

Description

technical field [0001] The present invention relates to a display device using a transmissive optical valve that modulates light emitted by a backlight to form an image. The invention also relates to display devices, such as projection displays, in which reflective light valves are used to modulate light. The light valve controls the amount of light that is visible on the screen. The term display will be used hereinafter without distinguishing between displays using reflective or transmissive light valves. Typically, each light valve represents a pixel of the image. In the case of color image reproduction, a triplet of light valves for the primary colors red, green, and blue can be used for one pixel, allowing multiple colors to be formed by mixing the primary colors accordingly. In this case, the backlight is typically a uniform white light. It is also possible to generate color images by sequentially generating monochrome images of primary colors. In this case, in the e...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G09G3/32G09G3/36G09G3/22
CPCG09G2320/0247G09G2320/064G09G3/3406
Inventor 迪迪尔·普洛奎因菲利普·马钱德杰勒德·莫里佐特
Owner THOMSON LICENSING SA