Thales

Laurent Canal

Yves Sontag

Gérard Voisin

Dorian Santiago

Philippe Airault

Gerard Voisin

The general field of the invention is that of the display devices that comprise an active liquid crystal matrix of twisted nematic type. The matrix comprises a set of pixels, a set of rows and of columns and an electronic control device. Each pixel is controlled by a transistor. The voltage applied to each control row is either a switch-on voltage VG_on sufficient to switch on the transistors, or a switch-off voltage VG_off sufficient to switch off the transistors. The voltage applied GMA to each column is dependent on the predetermined optical transmission of the pixel. The display device comprises means for detecting the correct operation of the electronic control device. In case of detection of incorrect operation, the display device comprises cut-off means arranged to force to zero the switch-off voltages VG_off of the rows and the GMA voltages of the columns, so that the transmission of all the pixels of the first set is minimum.

Secure display device with twisted nematic liquid crystal matrix

The general field of the invention is that of display devices including a liquid-crystal matrix screen composed of elementary pixels, said screen including at least a first electrode used as voltage reference and called the 'backplane,' a second electrode in the form of a matrix electronic network delivering the drive voltages for controlling the pixels and control electronics for said electrodes, said screen being used in the so-called 'normally black' mode, that is to say that in the absence of applied voltages, the optical transmission of the pixels is substantially zero. In the device according to the invention, the &#x201c;backplane&#x201d; drive voltage is a variable periodic voltage, the amplitude of variation of this voltage being sufficient so that in the absence of voltage on the second electrode, the optical transmission of the pixels is sufficient to be detected by an observer.

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Merignac, France

Laurent Canal