Printers and scanners are important peripheral devices. Printers transfer data from a computer onto paper using various technologies like impact, non-impact, inkjet, and laser. Scanners convert images and documents into digital form using linear sensors. Common scanner types include drum, flatbed, handheld, and photo scanners. Proper interfacing between devices and applications is important for functionality.

1. Printers
&
Scanners
Presented By-
Er. Sanyam S. Saini
ME (I&CE) (Regular)
2012-14

2. Printer
• Printer is a mechanical device for applying pressure to an inked
surface resting upon a medium such as paper or cloth, thereby
transferring an image.
• A printer is used to transfer data from a computer onto paper. The
paper copy obtained from a printer is often referred as printout
• An external hardware device responsible for taking computer data
and generating a hard copy of that data.
• Printers are one of the most commonly used peripherals and they
print text and still images on the paper.

4. Impact Printer
• These printers have a
mechanism that touches the
paper to create an image.
• These printers work by
banging a print head
containing a number of metal
pins which strike an inked
ribbon placed between the
print head and the paper.

5. Non-Impact Printer
• These printers create an
image on the print medium
without the use of force.
• They don’t touch the paper
while creating an image.
• Non-impact printers are much
quieter than impact printers
as they don’t strike the paper.

6. Dot-Matrix Printer
• The term dot matrix refers to the
process of placing dots to form an
image.
• Its speed is usually 30 to 550
characters per second (cps).
• This is the cheapest and the most noisy
printer and has a low print quality.
• Dot Matrix were 1st introduced by
Centronics in 1970.
How it works:-
• The dot matrix forms images one character at a time as the print head moves
across the paper.
• Uses tiny pins to hit an ink ribbon and the paper much as a typewriter does.
• This printer arranges dots to form characters and all kinds of images.
• 9 to 24 vertical column pins are contained in a rectangular print head. When
print head moves across the paper, pins are activated to form a dotted
character image. These printers can produce carbon copies along with the
originals.

7. Advantages & Disadvantages
Advantages Dis-advantages
(1) In-expensive. (1) Noisy
(2) Low per page cost. (2) Low resolution
(3) Energy efficient. (3) Limited fonts flexibility
(4) Poor quality graphics output.

8. Daisy Wheel Printer
• A daisy wheel printer is basically
an impact printer consisting of a
wheel and attached extensions on
which molded metal characters
are mounted.
• A daisy wheel printer produces
letter quality print and it can’t
produce graphics output.
How it works:-
• In a daisy wheel printer, a hammer presses the wheel against a
ribbon which in turn makes an ink stain on the paper in the form of
a character mounted on the wheel extensions.
• These printers are very noisy as there occur great movement during
the printing. Its printing speed is also very slow ,i.e. less than 90cps.

9. Ink-Jet Printer
• It is a non-impact printer producing a
high quality print. A standard Inkjet
printer has a resolution of 300dpi.
• Newer models have further improved
dpi.
• Inkjet printers were introduced in the
later half of 1980s and are very popular
owing to their extra-ordinary
performance.
How it works:-
• Print head having four ink cartridges moves .
• Software instructs where to apply dots of ink, which color and what
quantity to use.
• Electrical pulses are sent to the resistors behind each nozzle.
• Vapor bubbles of ink are formed by resistors and the ink is forced to the
paper through nozzles.
• A matrix of dots forms characters and pictures.

10. Advantages & Disadvantages
Advantages Dis-advantages
(1) High resolution output. (1) Expensive.
(2) Energy efficient. (2) Special paper required for
(3) Many options to select. higher resolution output.
(3) Time consuming in case of
graphics printing.

11. Thermal Printer
• Thermal printers are in-
expensive printers mostly used in
fax machines. The Thermal
printers are further classified
into two types.
(1) Electro thermal printers:
(2) Thermal Wax printers:
How it works:-
• Thermal printers use heated pins and ribbons with different color
bands.
• These printers contain a stick of wax like ink. The ribbon passes in
front of a print head that has a series of tiny heated pins.
• The pins cause the wax to melt and adhere to the paper and when
temperature reaches to a certain level, it is hardened.

12. Laser Printer
• Laser printers use very advanced
technology and produce a high
quality output.
• Laser printers can also produce
high quality graphics images.
• Resolution is 600 to 1200dpi.
How it works:-
• The OPC first must be charged before it will accept the image. A special
roller called the “Charging roller” applies the electrostatic charge uniformly
across the OPC .
• After the full width of an area of the OPC gets it charged, it rotates in front
of the modulated light beam.
• To form a visible image, a “developing roller” then dusts the OPC drum with
particles of tonner.
• The printer rolls the paper between the OPC drum & transfer roller , which
has strong electrostatic charge that attract the tonner off the drum.

13. Laser Printer
• To make image permanent , the printer squeezee the paper between
fuser & backup roller.
• Cleaning blade scrapes any leftover toner from it.

14. Multi-function Printer
• A multi function printer
abbreviated as MFP is an all
purpose device that
prints, faxes, copies and scans.
• A single multi function printer
can replace several bulky
devices.
• A multi function printer is also
known as AIO.
• These printers use inkjet
technology and provide high
quality print but at slow
speed.

15. Plotter
• A large scale printer which is very
accurate in producing engineering
drawings and architectural
blueprints.
• Two types of plotters are flatbed
and drum.
• Flatbed plotters are horizontally
aligned while drum plotters are
vertically positioned.

16. Different Printer & their Speed
S.No Type Mode of Printing Speed
Dot- Prints the character in dotted 200/300 to
1. Matrix pattern through ribbon using 700 CPS
either 24 pin or 9 pin
2. Ink-jet Slow , 90
Works by spraying ionized ink
CPS
3. Also called page printer. Uses
Laser 6 to 12 PPM
laser beam to produce an image.
Produces drawing or graph
4. Plotter through pens which are filled -----
with different colours.
CPS = Characters per Second; PPM = Page per Minute

17. Features of Printers
(1) Near typeset quality:
• A Lower quality print similar to the output of a type-writer.
(2) Letter quality:
• Print made up by fully formed (solid line) characters.
(3) Near letter quality:
• A print of high quality formed by multiple passes of print head over
the same letter.
(4) Standard quality:
• A high quality print formed by a single pass of the print head.
(5) Draft quality:
• A print formed with minimum number of dots or lines and are
smaller than the standard quality characters.

18. Factors Affecting Printing Quality
DPI:
• It is a measurement of printer’s resolution indicating how many
ink dots can be placed by the printer in one square inch. The higher
the DPI, the sharper is image.
Type of printer:
• Each type of printer has its own capabilities of printing. Some
types of printers produce high quality print while other produce
low quality print.
Print Mode:
• The printing mode may also affect the quality. For example the
draft mode increases the print rate but quality is reduced.
Toner:
• The quality and amount of toner also affects print quality.

19. Scanners
• To convert an existing drawing or photograph into electronic form.
• Scanner has a linear array of sensors, charge-coupled devices
(CCD), squeezed together hundreds per inch in a narrow strip that
stretches across the full width
• This line of sensors registers a single, thin line of the image at a time.
• Circuitry inside the scanner reads each sensing element one by one in
order, and creates a string of serial data representing the brightness
of each point in each individual scan line.
• Once the scanner collects and arranges the data of one line, it
advances to read the next line.

20. Types of Scanners
Drum Scanner or Page Scanner
• The image sensor to move across a
fixed original
• Drum scanner uses a linear array
so that a single spin of the drum
covers the entire image
• Paper wraps around a rotating
drum that spins the image past a
sensor string that’s fixed in place
inside the machine.
• Moderate in price
• Compact in size, because their
mechanisms are relatively simple.
• Only certain sizes of paper may be
accepted

21. Types of Scanners
Flat Bed Scanners
• Moves its line-up of sensors down the sheet.
• Flat glass surface on which the item be
scanned mused be placed
• Flat bed scanners have precision
mechanisms that step the sensors or
image, a small increment at a time, each
increment representing a single scan line.
• Movement of the mechanism, which is
carefully controlled by the electronics of the
scanner, determines the width of each line.
• Books, magazines, sections of poster can be
scanned

22. Types of Scanners
• T shaped hand scanner dragged across the
image to be scanned
• A string of sensors peers through a plastic
window to register the image
• Speed at which the hand is moved makes a
whole lot of difference
• Most hand scanners have a roller that
presses down against the image to sense how
fast the scanner is dragged.
• Compact, easy to carry and quick in using
• Adapt to non-flat surfaces and three
dimensional objects

23. Types of Scanners
Video Scanner
• Electronic equivalent of a photographic copy stand
• Operates like a camera- captures the entire image in a single look.
• Uses a conventional video camera to capture an image.
• Fast in operation, but low quality
• Video scanners require a CCD element for every pixel they scan, and
affordable two-dimensional CCD arrays have only a few hundred
thousand pixels.
• Resolution- pixels across the entire the image.

24. Types of Scanners
Photo Scanners
• Special purpose devices aimed at capturing digital images from
photographic prints.
• A flat bed scanner can do this, but it will be quicker and easier with a
dedicated device.
• A transmissive scanner rather than reflective
Slide Scanners
• It registers the light that is
transmitted through an image
• Source of illumination is on one side
and the image sensor is on the other
• The image must be on a transparent
medium

25. Features of Scanners
Colour
• Gray scale scanner are able to see only levels of brightness.
• Innately simpler, often faster and lower in cost.
• Monochrome Scanners are sufficient for some applications
Scanning Speed
• Earliest color scanners were three-pass machines, one pass for each of
the primary colours.
• Modern scanners use one-pass designs. They have a single light source
and rely on filtering to sort out the colors
• Pre-scan, relatively quick, low resulting pass across the
image, establishing the brightness range and target a specific area for
scanning. Then the actual scan at the required resolution.
• The interface used by a scanner influences the speed of scans – a slow
interface constricts the flow of huge amount of data.

26. Features of Scanners
Dynamic Range
• The compass of colors a scanner can discern is the scanner’s
dynamic range.
• Bit-depth - Number of bits needed to digitally encode the total color
capacity.
• 256 (8-bit), 1024 (10-bit), 4096 (12-bit) brightness levels in each
primary color.
• Bit-depth specifies the range of A-D converters that convert the level
detected by the scanner’s CCD sensors into digital signals.
• 8 bit to 24 bit color means the computer can display 256 to 16.7
million different hues

27. Features of Scanners
D-max
• The maximum image density that the scanner can handle.
• D-max indicates how dense an image can be before the scanner can no
longer distinguish the light shining through it.
• Any part of an image that’s more dense than the scanner’s D-max
rating, blocks up as solid black.
D-max = log (incident light/transmitted light)
• D-max of best slide scanners is 4.2. That means they can detect light
that’s diminished by a factor of more than 10000.

28. Features of Scanners
Resolution
• Smallest step that the sensor can advance.
• Resolution of a minimal scanner is about 300 dots per inch -
600, 1200, 2400 dpi.
• Represents the limit of the quality the scanner hardware is able to
resolve - hardware resolution.
• Interpolated resolution – control software of the scanner computes
additional dots in between those that are actually scanned, and thus
pushes the claimed resolution to 4800 or 9600 dpi.
• Adds no more information to the scan
• The greater number of dots reduces the jaggedness or stair-stepping in
the scan and makes lines looks smoother.

29. Features of Scanners
Light Sources
• Drum and Flatbed scanners – one or three cold cathode tubes
• Hand held Scanners – Light emitting diodes
• Slide scanners – source of transmitted light built in – transparency
adapter

30. Optical Character Recognition
• OCR software can convert into word processor, data base or
spreadsheet files.
• Matrix matching – small parts of each bit image it scanned is compared
to a library of bit patterns.
• It must be tuned to the particular typeface and type size scanned.
• Depends on the regular spacing between characters to determine the size
and shape of the character matrix.
• A matrix-matching OCR system must have either an enormous library
of bit patterns or the system must be limited to matching a few
typestyles and fonts.

31. Features of Scanners
Feature matching – analyze each bit pattern that is scanned.
• It derives the essential features of the character from the pattern of
bits – an up slope, a peak, and a down slope. In that every letter has
the same characteristic features.
• No need to know the size or font of the characters it is to recognize.
• No need of elaborate library of bit patterns.
Sheet Feeders
• Primarily used for OCR applications
• Automatically runs each sheet of a multiple page document
through a scanner.

32. Interfacing
Electrical Interfacing
Six different interfaces designs:
1. Small Computer System Interface (SCSI),
2. General Purpose Interface Bus (GPIB),
3. Standard serial,
4. Parallel,
5. USB,
6. Proprietary.
• Almost all current products rely on parallel, SCSI, or USB connections.
• Parallel models plug into legacy printer ports.
• Easy to plug in and get work done.
• Inexpensive, but slow performance.
• SCSI Interface is the fastest and easy to work with.
• A SCSI port is required. SCSI based scanners have their own SCSI host
adapters and cables.

33. Interfacing
Application Interfacing
Twain, released in 1992, is a scanner software interface standard developed
by a consortium of scanner and software makers.
• Twain is not an acronym, it derives from making the twain (two) meet, i.e.
applications and scanners
• Twain stands for “Technology Without An Interesting Name”
• Interface which brings together two entities, applications and input devices.
• Twain links programs and scanner hardware, giving software writers a
standard set of function calls by which to control the features of any scanner.
• Twain defines its hardware interface as its Source.
• Source is hardware or firmware in a scanner that controls the information
that flows from the scanner into Twain.
• The software links to the Twain source through Source Manager, which is a
set of program calls.

34. Conclusion
Before scanning any image consider:
1. what format you want (black & white, grayscale or color)
2. the resolution
3. preliminary scan is made to define the image area and dynamic
range.
4. make the final scan
5. before scanning, how to adjust the image with the graphic software
you use
6. crop off unwanted areas
7. shaper or soften the details
8. fine tune.
9. save the image for later use.

35. Questions asked in Previous Examination
1. Enlist different types of Scanners & explain their characteristics
, advantages, & disadvantages. (M.Imp)
2. Enlist different types of printers and explain the working of Laser
printer . (M.Imp)
3. Write short notes on printers & scanners.

36. Thank You