Scanners

1
Scanners

• The Basics

2
Overview

• What is a scanner?
• CCD and CID scanners
• How they work
• Advantages of each
• Other types of scanners
• Terms
• Interpolation
• Basic Scanning tools
• Advanced Scanning tools
• Demo
• Assignment

3
What Is a Scanner?

• A scanner is a piece of computer hardware that
  converts a 2D image into a electronic image
• Focus What was done before scanners?

4
Main Scanner Types

• CCD Scanner
• CID Scanner

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What is a CCD scanner?

• A scanner that uses a CCD (charged coupled
  device) to capture the scanned image
• CCD array of tiny light sensitive diodes called
  photosites that convert light into an electrical
  charge.

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CCD Scanners How They Work

• Shines light on a document
• Light reflecting off the document is captured by
  a CCD through a system of mirrors and lenses
• Electrical charge is created in CCD is converted
  into an image

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What is a CID Scanner?

• A scanner that uses LEDs to create light that is
  reflected into image sensors

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CIS Scanners How They Work

• contact image sensor (CIS) Contains rows of red,
  green and blue LEDs and image sensors.
• The LEDs combine to make white light
• Light reflected off the image is captured by the
  row of sensors.
• The CIS is located very close to the glass plate

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Notes CID printers

• Smaller than CID scanners (dont need system of
  mirrors and lenses)
• Requires little power to use
• Can run of power from USB port

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Notes CCD Printers

• Produce a higher quality image than CID
• Older technology
• Hook up via printer jack

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Types of scanners

• Flatbed scanners (desktop scanners)
• Document to be scanned is placed on glass
  flatbed, scanning head moves to scan image
• Most common type of scanner
• Sheet-fed scanners
• Like flatbed scanners but the paper moves over
  the scanning head
• Handheld scanners
• use the same basic technology as a flatbed
  scanner, but rely on the user to move them
  instead of a motorized belt.
• Fast but produces poor image quality
• Drum scanners.
• They use a technology called a photomultiplier
  tube (PMT).
• Used in graphics industry

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Additional Info on Scanners

• http//computer.howstuffworks.com/scanner.htm
• http//www.extremetech.com/article2/02C16972C394
  7782C00.asp
• http//photography.about.com/library/weekly/aa0602
  03a.htm

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Scanner Technical Info

• Bit Unit of computer information. Is either 1
  or 0.
• Pixel The basic unit of the composition of an
  image. A pixel may contain may bits
• Resolution The degree of sharpness of a
  displayed or printed character or image.
  Resolution is expressed as a matrix of pixels.

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Resolution and dpi

• Most flatbed scanners have a true hardware
  resolution of 300x300 dots per inch (dpi).
• The scanner's dpi is determined by
• the number of sensors in a single row
  (x-direction sampling rate) of the CCD or CIS
  array by the precision of the stepper motor
  (y-direction sampling rate)

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But Scanners claim a higher resolution output

• Interpolation - process that increases the
  resolution of an image
• Increases the resolution by adding extra pixels
  and selecting their color based on an average
  colors of it neighboring pixels
• Can produce high quality images

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Scanning an image scan tools

• Cropping - Cutting off the areas of a picture
  that are not wanted
• Flipping and Rotating Rotating the image so
  that its oriented as needed
• Alter the sharpness, contrast, brightness of an
  image
• Scan in black and white, grayscale and color

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Advanced Scanning Tool
Did you know you can

• Scan a document into Microsoft Word so it can be
  edited?
• Get rid of or moiré that may occur when scanning
  a picture from a magazine?

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Descreening

• Scanning technique that minimizes moire
• Most scanning software has a descreen option
• Activated by selecting descreen before scanning

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Effects of descreen
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OCR

• Technology that converts text from a scanned
  raster image into a text file so that it can be
  edited

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Summary - Scanners

• What is a scanner?
• CCD and CID scanners
• How they work
• Advantages of each
• Other types of scanners
• Terms
• Interpolation
• Basic Scanning tools
• Advanced Scanning tools
• Demo
• Assignment

22
Refrences

• www.howstuffworks.com