Method and devices for optimizing the contrast and the angle of view of a liquid crystal display
AssigneeSextant Avionique
InventorPierre Fagard
Life of this patent
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Abstract
A method is provided for optimizing the contrast and the angle of view of a liquid crystal display, this method consisting in periodically energizing a given zone of the display, permanently measuring the luminance of this zone so as to obtain at all times a pair of values corresponding respectively to the luminance of the zone in the energized state and to the luminance of the zone in the de-energized state, determining the contrast from the values of each of said pairs each of the measured luminance values and adjusting the control voltage of the cell display as a function of the contrast thus defined.
Claims6
A method of optimizing the contrast of a liquid crystal display controlled by a control voltage, in a determined angle of view, said method comprising the following phases of:
- i) energizing periodically a given zone of the liquid crystal display so as to cause it to pass successively from an energized "ON" state to a de-energized "OFF" state, then again to the energized "ON" state and so on;
- ii) measuring the luminance of said zone in said determined angle of view in each successive "ON" state"OFF" state pair, so as to obtain successive pairs of "ON"-"OFF" luminance values;
- iii) calculating a contrast value from each of said pairs of "ON"-"OFF" luminance values;
- iv. calculating a difference value between the contrast value determined at a time t and that determined at time t-1 and adjusting the control voltage of the liquid crystal display as a function of said difference value.
A device for optimizing the contrast of a transmissive type liquid crystal display provided with a plurality of electrodes, each defining a pixel, said device comprising:
- a control circuit adapted for applying to a determined number of said electrodes included in a given test zone of the liquid crystal display, a voltage causing periodic energization and de-energization of said determined number of electrodes,
- a photoelectric cell placed opposite said test zone so as to deliver a luminance signal having successive pairs of ON-OFF values corresponding to successive energized, de-energized states of said test zone,
- means for collimating and orienting the cell along a give axis which may correspond to a preferential axis of vision,
- a computer which receives said luminance signal and which calculates a contrast value at all times from said ON-OFF values of said successive pairs, said computer further calculating a difference value between a contrast value determined at a time t and that determined at a time t-1,
- adjusting means which act on the liquid crystal display as a function of said difference value, so as to obtain mamximum contrast.
Dependencies are inferred from the claim text.