EET 450 – Advanced DigitalVideo Display - CRTCRTSlide 4Slide 5Slide 6Slide 7CRT FaceSlide 9CRT CharacteristicsImage distortionSlide 12Display CharacteristicsDisplay characteristicsOther featuresFlat Panel SystemsLCD’sSlide 18Slide 19Other Flat panel technologiesSlide 21Slide 22Slide 23Slide 24Other Display UnitsConnectorsOther physical connectionsEET 450 – Advanced DigitalVideo Display SystemsVideo Display - CRTVideo displays convert the digital information stored in memory to some form of visible displayOriginally, the Cathode Ray Tube was usedElectrons were ‘boiled’ off of a plate, then accelerated to strike a plate covered in an phosphorThe phosphor glows due to the energy of the electronCRTBy controlling the position on the screen, and the intensity of the dot, intelligible information can be displayed. The CRT is a glass encapsulated array of electrodesContained in a vacuumRASTOR display versus VECTOR displayCRTCRTThe Electron gun is the cathode part of the displayElectrons are boiled off a beryllium plateThe electrons are accelerated by an electric potential with plates in the neckThe cloud of electrons is shaped into a beamThe electrons in the beam are accelerated by the attraction to the face (anode) of the CRTCRTAs the electron beam passes through the funnel on the way to the face, it is deflectedA raster display, sweeps from left to right/ top to bottom of the displayAs the face is ‘painted’ by the electron beam, the intensity of the beam is varied by control plates in the neck.At the face, the phosphor is struck by the electron beamCRTThe color of the spot of phosphor depends on which rare earth element is used in the phosphorMonochrome CRT’s use a single phosphorColor CRT’s use 3 primary colors of phosphors to obtain the RED, GREEN and BLUE The additive color blending scheme allows any color to be made from RGB combinationsCRT FaceThe phosphor is applied to the face in a variety of patterns. aperture shadow slot grill mask maskCRT FaceThe electron beam is further shaped by a metal ‘mask’ that allows the beam to strike only specific areas of the face‘Dot Pitch’ is the distance (in mm) from one group of dots to anotherCRT CharacteristicsThe shape of the face has much to do with distortions Screen curvatureResolutionVertical versus horizontal dotsAnti-glare treatmentScreen sizeAspect RatioImage distortionDistortion can be caused by maladjustment of the electronicsImage distortionThe beam must be adjusted to correctly strike the groups of phosphors which make up a pixelPurityLinearity adjustmentDisplay CharacteristicsInterlacingEach sweep of the face paints alternately even/odd lines•Keeps the required bandwidth downNon-interlaced displays are standard nowEach line is painted, every sweepSee table 17.3 for bandwidths of standard video displaysDisplay characteristicsThe vertical sweep is dependent on ‘sync’ frequencyMost monitors are now ‘multi-sync’ or multi frequencyTV’s are at a rate of 30 frames per secondCRTs for computers range from 30 to 80+ per second.Other featuresEnergy StarLow power requirementsSleep modeMonitor off (see the discussion from ‘power supply lecture on ‘green’ requirements.)Plug and PlayCRT’s now comply with PNP standardFlat Panel SystemsLCD – Nematic technologySupertwist, double supertwist, etc.Light is passed through a ‘liquid crystal’•Polarization of light•Dependent on electrical field•Passing light through a static polarizing filter, then through ‘spot’ of varying polarization, gives light/darkLCD’sLCD’s‘Spots’ of screen are passed through colored filters to provide RGB componentsThe eye blends spots into single colors.Alternative to Nematic technology LCD’s is Cholesteric TechnologyBi-stable – thus more energy efficient.LCD’sPassive matrixControl voltages are applied at edges of LCD panelHeat dissipation and contrast are a problemActive MatrixTransistors are embedded in the display panel.Power is applied to transistor, which amplifies contrast.Other Flat panel technologiesDSTNOther Flat panel technologiesField Emission displayOther Flat panel technologiesElectro-Luminescent display – LEDOther Flat panel technologiesGas Plasma (currently winning)Other Flat panel technologiesThin CRTOther Display UnitsProjection unitsOverhead display panelsVR Goggles3D glassesConnectorsCRT connectors are now standard at 15 pin high-density D-shell connectorReplaces 9 pin D connectorOther physical connectionsBNCEnhanced Video