Apparatus and method for providing a gray scale in liquid crystal flat panel displays

The method of implementing a gray scale for a pixel element in a liquid crystal display comprising the steps of:

• dividing said pixel element into a plurality of subpixel regions having substantially equal optical viewing areas, each of said subpixel regions including a region of liquid crystal material between optically transmitting conduction plates, said conducting plates forming a subpixel capacitor, all of said subpixel capacitors having substantially equal capacitances;
• fabricating a thin film transistor in each subpixel region, said thin film transistors having substantially equal threshold voltages;
• coupling an output terminal of each of said thin film transistors to a first conducting plate of a subpixel capacitor in a region including said thin film transistor;
• coupling input terminals of said thin film transistors of a pixel element to a one of a first multiplicity of conducting leads, said first multiplicity of conducting leads having signals related to a display image applied thereto;
• coupling control terminals of said thin film transistors of a pixel element to a one of a second multiplicity of conducting leads, said second multiplicity of conducting leads having signals related to pixel activation coupled thereto;
• and
• selecting parameters of each of said thin film transistors of each pixel element to provide differential charging of said coupled pixel element subpixel capacitor, each subpixel capacitor being charged during application of a control signal to said control terminals at a different rate determined by a magnitude of a voltage applied to said input terminals and said thin film transistor parameters, said equal area subpixel capacitor differential charging providing a subpixel gray scale determined by a different optical saturation voltage for each subpixel.

A liquid crystal display comprising:

• a first multiplicity of conducting leads;
• a second multiplicity of conducting leads;
• a multiplicity of display pixel elements, each of said pixel elements coupled to a one of said first multiplicity of conducting leads and to a one of said second multiplicity of conducting leads, each of said pixel elements including;
• a plurality of subpixel elements, each of said subpixel elements having,
• a liquid crystal material,
• a first and a second optically transmitting and electrically conducting plate on a first and second side of said liquid crystal material for providing a subpixel capacitor, each of said subpixel capacitors having substantially equal capacitances;
• and
• an active element having an output terminal coupled to said each subpixel capacitor, each active element of a pixel having an input lead coupled to said one of said first multiplicity of conducting leads, each active element of a pixel having a control terminal coupled to said one of said second multiplicity of conducting leads, each of said active elements having a substantially equal threshold voltage, wherein a control signal applied to said active element control terminal causes a charging of said coupled subpixel capacitor at a rate determined by a magnitude of an input voltage applied to said active element input lead and parameters of said active element, wherein each active element has different parameters, wherein a magnitude of an input signal applied to said pixel element along with a control signal and parameters of said pixel active elements result in a difference in charge stored on each subpixel capacitor, said difference in charge providing a gray scale for each pixel element by controlling a voltage across each subpixel capacitor, said gray scale determined by a saturation voltage for each subpixel capacitor.