Output devices

• Output device


  A peripheral that is used to output information
• Output device


  • A piece of hardware that takes data from within the computer and turns it into something that a human being can see and use e.g. showing an image on a screen, playing sound or printing a document
• Display


  An electronic device that outputs information via a screen or projection
• Types of screens


  • Screens / monitors
  • Projectors
  • LCD (Liquid Crystal Display)
  • LED (Light-Emitting Diodes)
  • LCD Projector
  • DLP (Digital Light Projector)
• Pixels


  Tiny illuminated dots that make up a display
• Resolution


  The amount of pixels the display contains
• Screen resolutions


  • Typical smartphone: 800 x 480
  • Typical tablet: 1280 x 800
  • Typical 13-inch laptop: 1280 x 800
  • Typical 19-inch desktop PC: 1440 x 900
  • 22-inch screen: 1920 x 1080
  • Typical Projector: 1024 x 768
  • Standard-definition TV: 1280 x 720
  • High-definition TV: 1920 x 1080
  • 4k TV: 3840 x 2160
• Monochrome


  Images with two colours: one foreground colour and one background colour, normally black and white
• Colour


  Images produced by mixing the three primary colours: red, green and blue (RGB)
• Colour depth


  • 1-bit monochrome: 2 colours
  • 8-bit grayscale: 256 shades
  • 8-bit colour: 256 colours
  • 16-bit colour (high colour): 65536 colours
  • 24-bit colour (true colour): 16777216 colours
  • 30, 36 or 48-bit colour (deep colour): Billions of colours
• Portrait display


  Squarer in nature, ratio of width to height of 4:3
• Landscape display


  Rectangular in nature, ratio of width to height of 16:9
• Portrait mode


  • Offers more height, best suited to viewing documents
• Landscape mode


  • Offers more width, best suited to viewing images and videos
• Display size


  Measured from one corner to the diagonally opposite corner, not height or width
• CRT (Cathode Ray Tube)


  • Former display screen, limited in resolution, bulky, uses a lot of energy, produces flickering images
• LCD (Liquid Crystal Display)


  • Produces sharp high resolution images, thin, low energy use, ideal for portable devices, do not damage eyes
• How LCD screens work

  Made up of liquid crystals that can be made transparent or solid by altering electric current, requiring backlighting as they don't produce light
• LED (Light Emitting Diode) display


  • More advanced than LCD, produces brighter and more direct light, smaller and thinner, wider viewing angle, less energy efficient
• How LED screens work

  Made up of tiny light emitting diodes that can be controlled to produce a vast range of colours
• In the past CCFLs (Cold Cathode Fluorescent lamps) were used as a backlight, but have been replaced by LEDs</b>
• OLED (Organic Light Emitting Diode)


  • Thinner, lighter and more flexible than LCD/LED, produce their own light so no backlight required, lower power consumption, wider viewing angle
• Advantages of OLED


  • Thinner and lighter layers
  • Brighter light
  • No backlight required
  • Lower power consumption
  • Can be made into large, thin sheets
  • Wide field of view
• Benefits of OLED


  • Produces own light so no backlight needed
  • Much lower power consumption
  • Greater field of view
  • Thinner and lighter than LCD
• Drawbacks of OLED


  • Higher production cost
  • Affected by water and contaminants
  • Shorter lifespan than LCD
• Uses of OLED


  Ideal for mobile devices due to mobility and battery life, ideal for modern TV screens due to brightness
• Advantages of flat-panel displays

  • High-resolution bright, flicker-free image
  • Can be made at ideal size for portable devices
  • Low energy requirements
• Disadvantages of flat-panel displays

  • Can be easily damaged if dropped
  • Can suffer from dead pixels
• Digital projector


  A display device connected to a computer that is used to project digital video output onto a flat area
• Digital projectors


  • Used to show output on a large scale, e.g. in business meetings, classrooms, conferences, but the greater the distance the dimmer the image
• Types of digital projectors

  • LCD (Liquid Crystal Display) projector
  • DLP (Digital Light Processing) projector
• How LCD projectors work

  1. Powerful white light beam generated

  2. Light beam sent to chromatic-coated mirrors that reflect different wavelengths

  3. Reflected light passes through 3 LCD screens to produce monochrome images

  4. Monochrome images recombined using a prism to produce full colour image

  5. Image projected through lens
• DLP (Digital Light Processing) projectors

  • Use millions of tiny mirrors to reflect light, create image with excellent colour reproduction but less contrast and brightness, smaller and more portable than LCD projectors
• Digital micromirror device (DMD) chip

  Contains several thousand microscopic mirrors that can tilt towards or away from light source to create light or dark pixels
• Advantages of DLP projectors

  • Higher contrast ratios
  • Higher reliability/longevity
  • Quieter running
  • No issues lining up images
• Disadvantages of DLP projectors

  • Image tends to suffer from 'shadows' when showing moving images
  • Colour definition not as good as LCD due to lower colour saturation
• Advantages of LCD projectors

  • Give a sharper image than DLP
  • Better colour saturation than DLP
  • More energy efficient than DLP
• Disadvantages of LCD projectors

  • Contrast ratios not as good as DLP
  • Limited lifespan, screens degrade over time
• Printers


  Produce hard copies (printouts) of information
• Printers


  • Printout can be taken away, shared or kept as a permanent record
  • Some produce monochrome (black and white) printouts, others produce colour using CMYK (cyan, magenta, yellow, black)