Write short note on : i. Plasma panel ii. LCD

1. Plasma panel :-

• Plasma panels, also called gas discharge displays, are constructed by filling the region between two glass plates with a mixture of gases that usually includes neon.

• A series of vertical conducting ribbons is placed on one glass panel and a set of horizontal ribbons is built into the other glass panel.

• Firing voltages applied to a pair of horizontal and vertical conductors cause the gas at the intersection of the two conductors to break down into glowing plasma of electrons and ions.

• Picture definition is stored in a refresh buffer, and the firing voltages are applied to refresh the pixel positions (at the intersections of the conductors) 60 times per second.

• Alternating current methods are used to provide faster application of the firing voltages, and thus brighter displays. Separation between pixels is provided by the electric field of the conductors.

1. Liquid Crystal Displays (LCDs) :-

• LCDs are non-emissive devices which produce a picture by passing polarized light from the surroundings of an internal light source through a liquid crystal material.

• Liquid crystals are almost transparent substances, exhibiting the properties of both solid and liquid matter.

• Light passing through liquid crystals change their molecular alignment and consequently the way light passed through them.

• In LCDs, liquid crystals are sandwiched between thin polarized sheets that are used.

• Liquid crystal displays are used in miniature televisions and video cameras and monitors.