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Adaptive incremental sub-frame driving method for displays employing light recycling

IP.com Disclosure Number: IPCOM000032011D
Publication Date: 2004-Oct-19
Document File: 6 page(s) / 24K

Publishing Venue

The IP.com Prior Art Database

Abstract

ID697846

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Adaptive incremental sub-frame driving method for displays employing light recycling

The invention relates to a method for driving a light valve display. The method comprises a sub-frame modulation scheme for obtaining gray-values according to image information to be displayed. Examples of a display system wherein this method can be applied are a dynamic foil display or a digital mirror display. Light recycling in displays introduces a higher efficiency and an improved dynamic brightness range of the displays. Light recycling may be particularly interesting for mobile applications where low power consumption is a prerequisite.

    A problem in conventional light recycling methods is that the absolute brightness at a predetermined position on the display depe nds on the content of surrounding area in the displayed picture and more generally on the content on the displayed picture as a whole. In order to achieve a controllable predetermined brightness, an overall correction must be made, for instance by dimming the lamp or light source. If light recycling were to be applied to a conventional amplitude- modulated display like e.g. an LCD this would be a rather straightforward operation. However, for a driving method comprising a sub-frame modulation scheme the image content is different for the different sub-frames within one frame and a simple correction will not be sufficient.

    The invention proposes a robust adaptive incremental sub-frame driving method, which enables light recycling and which is robust against non-uniformities and contouring artifacts.

    In sub-frame driven displays the intensity modulation is achieved by a method comprising a step of splitting the frame time into different sub-frames and a step of switching the individual pixels either "on" or "off" during each sub-frame. The weight of each sub-frame is determined by its duration and/or by its intensity.

Some sub-frame addressed displays may potentially employ the concept of light recycling. Examples of such displays are the foil display and projection display comprising a DMD. Both displays are schematically shown in figure 1 and 2 respectively.

    Fig.1 shows a dynamic foil display 1 comprising a light guide 2, a membrane 3 and a second plate 4. Furthermore, the foil display comprises electrode systems 5 and 6 arranged, respectively, on the surface of the light guide 2 facing the membrane 3 and on the surface of the second plate 4 facing the membrane. Preferably, a common ITO electrode 7 is arranged on a surface of the membrane 3. The electrodes 5 and 6 form two sets of electrodes, which cross each other at an angle of preferably 90o; respectively a set of selection electrodes or row electrodes 6 and a set of data electrodes or column electrodes 5. The display device 1 further comprises a light source 9. Light guide 2 has a light input in which light generated by the light source 9 is coupled into the light guide 2. The light source may emit white light, or light of any...