Thales

Gérard Voisin

Hugues Lebrun

Thierry Kretz

Laurent Canal

Philippe Airault

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.

Display device including a liquid crystal screen with secured display

An integrated method of detecting an image defect in an LCD screen consists in verifying the consumption of current on a power supply bus of the image display means (row driver, column driver, counter electrode CE), during capacitive charges or discharges of the selection lines Land/or columns Col. The method comprises the integration of a current measurement chain comprising a measurement resistor Rm on the power supply bus and measurementand comparisoncircuits providing outside the screen a detection signal Sd which is processed by an external circuit for safety management.

Integrated method of detecting an image defect in a liquid crystal screen

A shift register driven by two complementary clock signals is integrated on an active-matrix substrate of a flat screen for controlling selection of rows of image points of the flat screen is disclosed. The shift register includes a control transistor driven by one of the clock signals, and connected between this clock signal and an output node connected to a corresponding row. The shift register also includes a capacitor connected between an internal node connected to the gate of the control transistor. The output node is discharged each time the flat screen starts.

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Saint Medard en Jalles, France

Gérard Voisin