Liquid crystal display systems

An alternating current drive circuit for a liquid crystal display unit, said display unit being adapted for connection to a source of image signals, one of said image signals being inverted, comprising:

• a plurality of liquid crystal picture elements, said picture elements being arranged in a fixed pattern, each picture element having a picture element electrode;
• a picture element selecting transistor and a capacitor associated with each of said picture elements, and connected to the associated picture element electrode, said capacitors having first electrodes coupled to one of a plurality of common capacitor electrodes, a plurality of said capacitors being connected to every common capacitor electrode;
• means for selecting picture elements for display of said image signals, each said picture element electrode being connected periodically to said means for selecting through said associated transistor;
• a reference voltage source outputting a reference voltage, said reference voltage source being connected to every picture element at the electrode opposite to said picture element electrode;
• voltage means, said voltage means being adapted to output a plurality of voltage levels said voltage changing periodically, each said common capacitor electrode being connected in turn to the output of said voltage means, said periodic level change of said voltage means produces an AC signal across said picture element relative to said reference voltage.