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Scanner. Computer Peripherals First Semester Second year Faculty of computers and information. Scanner Types. Flatbed scanners (desktop scanners) The most versatile and commonly used scanners. Sheet-fed scanners

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  1. Scanner Computer Peripherals First Semester Second year Faculty of computers and information

  2. Scanner Types • Flatbed scanners (desktop scanners) • The most versatile and commonly used scanners. • Sheet-fed scanners • similar to flatbed scanners except the document is moved and the scan head is immobile. • Handheld scanners • similar to flatbed scanner, but rely on the user to move them instead of a motorized belt. • Less quality. • Drum scanners • are used by the publishing industry to capture incredibly detailed images. They use a technology called a photomultiplier tube (PMT). In PMT, the document to be scanned is mounted on a glass cylinder. At the center of the cylinder is a sensor that splits light bounced from the document into three beams. Each beam is sent through a color filter into a photomultiplier tube where the light is changed into an electrical signal.

  3. Flatbed scanners Sheet-fed scanners

  4. Handheld scanners Drum scanners

  5. Scanner • Charge-coupled device (CCD) array • Mirrors (2 or 3) • Scan head • Glass plate • Lamp • Lens • Cover • Filters • Stepper motor • Stabilizer bar • Belt • Power supply • Interface port (s) • Control circuitry

  6. Charge-coupled device (CCD) array • CCD is a collection of tiny light-sensitivediodes, which convert photons (light) into electrons (electrical charge). • These diodes are calledphotosites. In a nutshell, each photosite is sensitive to light -- the brighter the light that hits a single photosite, the greater the electrical charge that will accumulate at that site. • The image of the document that you scan reaches the CCD array through a series of mirrors, filters and lenses.

  7. The Scanning Process • The document is placed on theglass plateand thecoveris closed (white or black) background that the scanner software can use as a reference point for determining the size of the document being scanned. • A fluorescentlamp is used to illuminate the document.

  8. The Scanning Process • The scan head (mirrors, lens, filter and CCD array) is moved slowly across the document by abeltthat is attached to a stepper motor. The scan head is attached to astabilizerbarto ensure that there is no wobble or deviation in thepass.

  9. The Scanning Process • The image of the document is reflected by an angledmirrorto another mirror (to focus the image it reflects onto a smaller surface). • The last mirror reflects the image onto alens. The lens focuses the image through afilteron the CCD array. • The filter and lens arrangement vary based on the scanner. • Three passscanning • Each pass uses a different color filter (red, green or blue) between the lens and CCD array. • Single pass scanning • The lens splits the image into three smaller versions of the original. Each smaller version passes through a color filter (either red, green or blue) onto a discrete section of the CCD array.

  10. The Scanning Process

  11. The Scanning Process • Contact image sensor (CIS) • CIS replaces the CCD array, mirrors, filters, lamp and lens with rows of red, green and blue light emitting diodes (LEDs). • When the image is scanned, the LEDs combine to provide white light. The illuminated image is then captured by the row of sensors. • cheaper, lighter and thinner • less quality and resolution

  12. Resolution and Interpolation • Resolution • x-direction sampling rate (number of sensors in a single row ( • y-direction sampling rate(precision of the stepper motor) • Sharpness • depends on the quality of the lens and the brightness of the light source. • Interpolation • a process that the scanning software uses to increase the resolution of an image. • It does this by creating extra pixels in between the ones actually scanned by the CCD array (300x300 to 600x300) • Bit depth (color depth) • The number of colors that the scanner is capable of reproducing

  13. Image Transfer • Parallel • (Universal Serial Bus (USB • (Small Computer System Interface (SCSI • FireWire

  14. Image Transfer • TWAIN is known as Technology Without An Interesting Name! • TWAIN , most scanners speak a common language • The TWAIN driver acts as an interpreter between any application that supports the TWAIN standard and the scanner. • OCR software allows you to scan in words from a document and convert them into computer-based text.

  15. That’s it! Thanks for your attention

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