Thomson Licensing

Pierrick Martin

Philippe Le Roy

Christophe Prat

Dominique Gagnot

A video display device comprises a plurality of light emitting elements arranged in a matrix having rows and columns; a plurality of first current modulators each of which is associated to one of said light emitting elements for drawing a feed current of programmable intensity for the associated light emitting element from a circuit node associated to each of said columns; a current generator controlled by video data representative of desired luminosities of said light emitting elements for supplying a first current (I)to said circuit node, the intensity of which is representative of a desired luminosity of at least one of said light emitting elements; the circuit node having a specific voltage level when the intensity supplied by said current generator is drawn from the current node by the first current modulator associated to said at least one light emitting element; a second current modulator for supplying a second current (I) to said circuit node; a comparator having inputs connected to said circuit node and to a reference terminal which is constantly held at said specific voltage level and an output connected to a control input of said second current modulator, whereby the second current (I) from said second current modulator is controlled so as to yield said specific voltage level at the circuit node.

Video display device and operating method therefore

The display comprises an array of pixel circuits each comprising an emitterin series with a current modulation transistor, and at least one address circuit, which integrates, for each column, a differential amplifier and a passive element preferably a resistive element, which cooperate with the current modulation transistors so as to form, during address phases in which the emitters are switched 'out of the circuit', a voltage-programmable current generator. After the address phases, thanks to a suitable switch, the emitters are switched 'into the circuit' and supplied with the preprogrammed current. Such a display allows the image display quality to be inexpensively improved.

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Rennes, France

Pierrick Martin