1 / 27

EET 450 – Advanced Digital

EET 450 – Advanced Digital. Video Display Systems. Video Display - CRT. Video displays convert the digital information stored in memory to some form of visible display Originally, the Cathode Ray Tube was used

hani
Download Presentation

EET 450 – Advanced Digital

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. EET 450 – Advanced Digital Video Display Systems

  2. Video Display - CRT • Video displays convert the digital information stored in memory to some form of visible display • Originally, the Cathode Ray Tube was used • Electrons were ‘boiled’ off of a plate, then accelerated to strike a plate covered in an phosphor • The phosphor glows due to the energy of the electron

  3. CRT • By 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 electrodes • Contained in a vacuum • RASTOR display versus VECTOR display

  4. CRT

  5. CRT • The Electron gun is the cathode part of the display • Electrons are boiled off a beryllium plate • The electrons are accelerated by an electric potential with plates in the neck • The cloud of electrons is shaped into a beam • The electrons in the beam are accelerated by the attraction to the face (anode) of the CRT

  6. CRT • As the electron beam passes through the funnel on the way to the face, it is deflected • A raster display, sweeps from left to right/ top to bottom of the display • As 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 beam

  7. CRT • The color of the spot of phosphor depends on which rare earth element is used in the phosphor • Monochrome CRT’s use a single phosphor • Color 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 combinations

  8. CRT Face • The phosphor is applied to the face in a variety of patterns. aperture shadow slot grill mask mask

  9. CRT Face • The 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 another

  10. CRT Characteristics • The shape of the face has much to do with distortions • Screen curvature • Resolution • Vertical versus horizontal dots • Anti-glare treatment • Screen size • Aspect Ratio

  11. Image distortion • Distortion can be caused by maladjustment of the electronics

  12. Image distortion • The beam must be adjusted to correctly strike the groups of phosphors which make up a pixel • Purity • Linearity adjustment

  13. Display Characteristics • Interlacing • Each sweep of the face paints alternately even/odd lines • Keeps the required bandwidth down • Non-interlaced displays are standard now • Each line is painted, every sweep • See table 17.3 for bandwidths of standard video displays

  14. Display characteristics • The vertical sweep is dependent on ‘sync’ frequency • Most monitors are now ‘multi-sync’ or multi frequency • TV’s are at a rate of 30 frames per second • CRTs for computers range from 30 to 80+ per second.

  15. Other features • Energy Star • Low power requirements • Sleep mode • Monitor off (see the discussion from ‘power supply lecture on ‘green’ requirements.) • Plug and Play • CRT’s now comply with PNP standard

  16. Flat Panel Systems • LCD – Nematic technology • Supertwist, 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/dark

  17. LCD’s

  18. LCD’s • ‘Spots’ of screen are passed through colored filters to provide RGB components • The eye blends spots into single colors. • Alternative to Nematic technology LCD’s is Cholesteric Technology • Bi-stable – thus more energy efficient.

  19. LCD’s • Passive matrix • Control voltages are applied at edges of LCD panel • Heat dissipation and contrast are a problem • Active Matrix • Transistors are embedded in the display panel. • Power is applied to transistor, which amplifies contrast.

  20. Other Flat panel technologies • DSTN

  21. Other Flat panel technologies • Field Emission display

  22. Other Flat panel technologies • Electro-Luminescent display – LED

  23. Other Flat panel technologies • Gas Plasma (currently winning)

  24. Other Flat panel technologies • Thin CRT

  25. Other Display Units • Projection units • Overhead display panels • VR Goggles • 3D glasses

  26. Connectors • CRT connectors are now standard at 15 pin high-density D-shell connector • Replaces 9 pin D connector

  27. Other physical connections • BNC • Enhanced Video Connector

More Related