Sextant Avionique

Thomson-csf Sextant

Thomson-csf

Laurent Georges

Laurent Bignolles

Jean-Claude Lehureau

Bertrand Morbieu

Frederic De Lauzun

Fran&ccedil;ois Lopez

Jean-Jacques Laborie

Fr&eacute;d&eacute;ric De Lauzun

To obtain improved readability of a liquid crystal display screen under varied conditions of ambient luminosity, it is possible to increase the dynamic range of variation of the polarizing voltage. However, this leads to an increase in the electrical power consumption and to contrast reversal defects. To prevent this phenomenon, it is proposed not to modify the dynamic range of variation of polarizing voltage but to shift this range towards the lower voltages when the ambient luminosity increases or towards the higher voltages when the ambient luminosity diminishes. Thus, the white level is favored under high ambient luminosity and the black level is favored under low or normal luminosity.

Method and device for the polarizing of an LCD screen as a function of the ambient luminosity

A display device with a liquid crystal cell including a layer of twisted nematic liquid crystal placed between two polarizers and including, between the liquid crystal layer and each of the polarizers, a structure for compensating for cell contrast variations according to the observation angle which has an orientation in the plane of the cell. The pass directions of the polarizers are separated by an angle of 90&plus;A degrees, in which A is not zero, and the orientations of the two compensation structures are separated by an angle of 90&plus;B degrees, in which B is not zero. Such a structure may find particular application to a liquid crystal screen, especially for avionics.

Method and apparatus for improving the viewing angle of an LCD screen by twisting the polarizers and compensating structures

The present invention relates to a display device with a liquid-crystal cell comprising a twisted nematic liquid-crystal layer ( ) placed between two crossed polarizers ( ) and comprising, between the liquid-crystal layer and at least one of the polarizers, a structure for compensating for the variations in contrast of the cell according to the angle of observation. This structure comprises at least two superposed negative uniaxial media such that the extraordinary optical axis of one medium ( ) is parallel to the normal to the cell and that of the other medium ( ) is inclined with respect to this normal on the one hand and with respect to the plane of the cell on the other. This compensating structure includes an additional layer ( ) of a positive uniaxial birefringent material.

Angle of view of a LCD screen by a novel birefringent film stacking

Display panel with compensation by holographic birefringent films

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Bordeaux, France

Laurent Georges