display devices - by sumithra
TRANSCRIPT
WELCOME
DISPLAY DEVICES
The display devices of the older times are called as vector displays.
The e important terms associated with display devices are:
Resolution: the maximum number of points the at can be displayed without
overlap is called resolution.Aspect ratio : this term gives the ratio of vertical pixel to the horizontal pixel.
CATHODE RAY TUBE (CRT)
A beam of electrons is emitted by the electron gun . the beam passes through the various focusing and deflection systems.
The aim of the systems is to direct the beam to specified points on the screen. The screen is phosphorous coated.
The phosphorous has the property a beam strikes on the screen it emits small spot of light.
Redirecting the electron beam at certain interval by redrawing the picture.
Heat is supplied to the electron gun which causes an electron beam to be accelerated towards the phosphorous
coated screen.Control grid controls the intensity of the
electron beam.Electro static deflections are normally
used in televisions & computers monitors.The beam passes through two pair of
metal plates.One pair of vertical plates & another pair
of horizontal plates.In the vertical plates bend the beam to the left or right & horizontal plates bend
the beam to the top or bottom.
COLOR CRT MONITORS•Two basic methods are used display in CRT which displays color images.
Beam penetration methodShadow mask method
Shadow mask method
•In the shadow mask method the screen has three phosphor color dots at each pixel point. •One phosphor emits red light, another emits green light and the third emits blue light.•Three electron guns
are used one for each dot.•A grid called shadow mask is placed just behind the phosphor screen.
•The three electron beams are deflected and focused on to the shadow mask.•They activate a dot triangle, which appears as a small color dot on the screen.•Activating only one of the electron guns produces the three colors on the screen.
PLASMA PANEL DISPLAY
•A plasma display panel(PDP) is a type of flat panel display now commonly used for large TV displays(32 inch)•In plasma display a gas in the cells is electrically turned into plasma then excites phosphorus to emit light •The two glass plates with neon and xenon gas. •A series of vertical and horizontal electrodes are placed on the front and rare glass plates. •These electrodes are used to light up the gas into small “bulb” with a centre glass plates containing a number of clearly spaced holes as shown in the figure.
Horizontal electrodes.
Dielectric glass.
Vertical electrodes.
Substrate glass
PLASMA PANEL DISPLAY.
Thank you!