METHOD FOR ADDRESSING EACH COLUMN OF A MATRIX TYPE LIQUID CRYSTAL DISPLAY PANEL.
The present invention relates to an addressing method for every column (cl) of a matrix LCD screen comprising production of a control pulse by a transistor (3) driving the said column, the said pulse having a duration determined by the value of the sample of a video input signal, the said pulse acting on the conduction state of the said transistor in order to connect the said column to a supply terminal where a voltage ramp (2) is developed. In accordance with the method, two pulse durations are alternated, whose sum is predetermined and so that a given value of the sample of a video signal produces the same optical effect from one period to the next, differentiated excitation voltages are employed on at least one of the framing electrodes of the liquid crystal layer, namely the said column (cl) and its counter-electrode (CE). Application especially to active matrix LCD screens. i method of addressing each column of a matrix type LCD comprising producing a control pulse of a transistor [...] of said column, said pulse having a duration determined by the value of the sample of input video signal, said pulse acting on the conduction state of said transistor for connecting said column to a power supply terminal which develops a voltage ramp, characterized in that the alternating between two pulse widths whose sum is predetermined and in order for a given value of the sample of video signal produces the same optical effect of one period to the next, are implemented the excitation voltages differentiated on at least one of the electrodes for frames of the liquid crystal layer, namely said column and its counter electrode. 2. the addressing method according to claim 1, characterized in that, before conversion, the is periodically reversed the video signal so as to obtain, after conversion, during a first time period a pulse duration (T-) for a second period and a pulse duration (T-T), (T-) represents the duration of the period. 3. method according to claim 1, characterized in that when an AC voltage is applied periodically over the counter electrode, the same ramp voltage is applied to each period. 4. method according to claim 1, characterized in that when a fixed voltage is applied to the counter electrode, the voltage ramp is offset symmetrically to each period with respect to the fixed voltage so as Way applying a ramp varying between V and V 'during a first period and a ramp varying between - the V' and - V during a second period. The method of any of claims 1 to 4 lG, characterized in that the period (T-) corresponds to a frame. 6. method according to any one of claims 1 to 5, characterized in that the LCD panel is an active matrix display. 7. method according to any one of claims 1 to 6, characterized in that the applied to the counter electrode DC offset voltage compensating for the offset means the threshold voltages of the switching transistors.