LIS508 lecture 6: output devices

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LIS508 lecture 6 output devices

• Thomas Krichel
• 2002-10-27

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Structure

• Fundamental concepts
• Printers
• Monitors
• only at the simplest level
• More detailed level not required

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Fundamental concepts I

• Pixel
• A very small element of a picture
• Inside the pixel color and brightness is fixed
• All the pixels are created by the computer
• Resolution
• Number of pixels per inch
• Or total number of pixels, confusion

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Fundamental concepts II

• Red-blue-green model.
• Add colors red blue and green to various degrees
  to get pixels of any color
• Additive model
• Cyan-Magenta-Yellow
• Uses basic color cyan, magenta, yellow, to absorb
  light on the surface
• Subtractive color model

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Output comes in two forms

• Tangible or hardcopy output
• Card puncher
• Printer
• Intangible or softcopy output
• Monitor display screens
• Loudspeaker output

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Hardcopy to printers

• Printer prints
• character symbols
• Graphics
• Output quality is measured in dpi dots per inch
• Printers vary from 60 to 1500 dpi
• 600 dpi seems common

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Types of printers impact

• Forms characters or images by mechanic strikes of
  a print hammer or wheel.
• One example is a typewriter.
• Most common form is the dot matrix printer
• Head with small pins (9, 18, 24)
• Strike ribbon against paper
• Do 72 to 144 dpi, 30 to 400 chars
• Noisy
• Image may smear

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Types of printers non-impact

• Form characters and images without physical
  contact
• Less moving parts, less noise
• Three forms
• Laser printer
• Inkjet printer
• Thermal printer (less frequent)

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Laser printer

• Images are produced on a drum
• A laser beam sets electrical charge on dots on
  the drum
• Magnetically charged powder called toner flies to
  the electrified dots on the drum
• The drum rolls the toner on the paper
• A second drum burns the toner on the paper

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Laser printer performance

• Can print 200 pages per minute provided that the
  computer can chunk out the data that fast
• Can print a lot of different fonts
• More fancy models can even do color
• Use a page description language to generate the
  images

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Inkjet printer

• Spray tiny, electrically charged drops of ink
  from 64 nozzles through holes in a matrix onto
  paper
• There are usually four cartages of colored ink
  (cyan, magenta, yellow, black)
• Head moves around and software says where to
  spray

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Inkjet printer performance

• Can print color at much less cost than laser
  printer
• Lower resolution than a color laser printer
• Slow, one page may take up to 10 minutes
• More expensive to operate than a color laser
  printer when you have to print a lot of color.

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Other printers

• Thermal printers
• use wax and heat to burn images on special paper
• Expensive to buy, and paper is expensive.
• Only for those who require top quality.
• Multifunction printer
• Device that can print, scan, copy and fax
• When one component is kaputt, you can not indulge
  in any of the activities

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Softcopy output monitor

• Size is measured diagonally from corner to corner
  in inches, not the size of the viewing area
• Common sizes are 13, 15, 17, 19, 21
• There are two types
• Cathode-ray tube CRT
• Flat panel displays
• All display an image through a number of pixels,
  individual dots that make it up

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Display quality

• Dot pitch is the amount of space between adjacent
  pixels, usually measure in millimeters
• Resolution is the number of pixels measured as
  horizontal pixel number vertical pixel number.
• Refresh rate is the number of times per second
  the pixels are recharged. gt 75 is ok
• Color dept, 8bit, 16bit and 32bit, true color. It
  is often not necessary to have true color. It is
  better to have higher resolution and less colors.

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Types of flat panel monitors

• Passive matrix display one transistor controls a
  whole row or column of pixels.
• good for monochrome
• but not for color.
• less expensive
• Lower energy consumption
• Active matrix display, aka thin film transmission
  TFT each pixel has its own transistor

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CRT monitors

• Have a three rays that paint red blue and green
• They emit beams that hit phosphate in the screen
  surface
• Light is emitted
• Analogue technology

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Moving from CRT to TFT

• Video card still emit analog beam signals to the
  monitor.
• They have to be converted to the flat panel
  signal that is digital
• Causes some performance losses.
• Slow conversion to flat panel technology
• Likely to be taken up outside IT, like in art for
  example

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• Thank you for your attention!