Printers &

Scanners Presented By-

Er. Sanyam S. SainiME (I&CE) (Regular)

2012-14

Printer

• Printer is a mechanical device for applying pressure to an inkedsurface resting upon a medium such as paper or cloth, therebytransferring an image.

• A printer is used to transfer data from a computer onto paper. Thepaper copy obtained from a printer is often referred as printout

• An external hardware device responsible for taking computer dataand generating a hard copy of that data.

• Printers are one of the most commonly used peripherals and theyprint text and still images on the paper.

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.

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.

Dot-Matrix Printer

• The term dot matrix refers to theprocess of placing dots to form animage.

• Its speed is usually 30 to 550characters per second (cps).

• This is the cheapest and the most noisyprinter and has a low print quality.

• Dot Matrix were 1st introduced byCentronics in 1970.

• The dot matrix forms images one character at a time as the print head movesacross 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. Whenprint head moves across the paper, pins are activated to form a dottedcharacter image. These printers can produce carbon copies along with theoriginals.

How it works:-

Advantages & Disadvantages

(1) In-expensive.

(2) Low per page cost.

(3) Energy efficient.

(1) Noisy

(2) Low resolution

(3) Limited fonts flexibility

(4) Poor quality graphics output.

Advantages Dis-advantages

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.

• 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.

How it works:-

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.

• 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.

How it works:-

Advantages & Disadvantages

(1) High resolution output.(2) Energy efficient.(3) Many options to select.

(1) Expensive.(2) Special paper required for higher resolution output.(3) Time consuming in case of graphics printing.

Advantages Dis-advantages

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:

• 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.

How it works:-

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.

• The OPC first must be charged before it will accept the image. A specialroller called the “Charging roller” applies the electrostatic charge uniformlyacross the OPC .

• After the full width of an area of the OPC gets it charged, it rotates in frontof the modulated light beam.

• To form a visible image, a “developing roller” then dusts the OPC drum withparticles of tonner.

• The printer rolls the paper between the OPC drum & transfer roller , whichhas strong electrostatic charge that attract the tonner off the drum.

How it works:-

Laser Printer

• To make image permanent , the printer squeezee the paper betweenfuser & backup roller.

• Cleaning blade scrapes any leftover toner from it.

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.

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.

Different Printer & their Speed

S.No Type Mode of Printing Speed

1.Dot-

Matrix

Prints the character in dotted pattern through ribbon using either 24 pin or 9 pin

200/300 to 700 CPS

2. Ink-jet Works by spraying ionized inkSlow , 90 CPS

3. Laser Also called page printer. Uses laser beam to produce an image. 6 to 12 PPM

4. Plotter

Produces drawing or graph through pens which are filled with different colours.

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CPS = Characters per Second; PPM = Page per Minute

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.

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.

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 thatstretches 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 inorder, and creates a string of serial data representing the brightnessof each point in each individual scan line.

• Once the scanner collects and arranges the data of one line, itadvances to read the next line.

Types of Scanners

• 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 rotatingdrum that spins the image past asensor string that’s fixed in placeinside the machine.

• Moderate in price

• Compact in size, because theirmechanisms are relatively simple.

• Only certain sizes of paper may beaccepted

Drum Scanner or Page Scanner

Types of Scanners

• Moves its line-up of sensors down the sheet.

• Flat glass surface on which the item bescanned mused be placed

• Flat bed scanners have precisionmechanisms that step the sensors orimage, a small increment at a time, eachincrement representing a single scan line.

• Movement of the mechanism, which iscarefully controlled by the electronics of thescanner, determines the width of each line.

• Books, magazines, sections of poster can bescanned

Flat Bed Scanners

• T shaped hand scanner dragged across theimage to be scanned

• A string of sensors peers through a plasticwindow to register the image

• Speed at which the hand is moved makes awhole lot of difference

• Most hand scanners have a roller thatpresses down against the image to sense howfast the scanner is dragged.

• Compact, easy to carry and quick in using

• Adapt to non-flat surfaces and threedimensional objects

Types of Scanners

• 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, andaffordable two-dimensional CCD arrays have only a few hundredthousand pixels.

• Resolution- pixels across the entire the image.

Types of Scanners

Video Scanner

• Special purpose devices aimed at capturing digital images fromphotographic prints.

• A flat bed scanner can do this, but it will be quicker and easier with adedicated device.

• A transmissive scanner rather than reflective

Types of Scanners

Photo Scanners

Slide Scanners

• It registers the light that istransmitted through an image

• Source of illumination is on one sideand the image sensor is on the other

• The image must be on a transparentmedium

Features of Scanners

• 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

Colour

Scanning Speed

• Earliest color scanners were three-pass machines, one pass for each ofthe primary colours.

• Modern scanners use one-pass designs. They have a single light sourceand rely on filtering to sort out the colors

• Pre-scan, relatively quick, low resulting pass across theimage, establishing the brightness range and target a specific area forscanning. Then the actual scan at the required resolution.

• The interface used by a scanner influences the speed of scans – a slowinterface constricts the flow of huge amount of data.

• The compass of colors a scanner can discern is the scanner’sdynamic range.

• Bit-depth - Number of bits needed to digitally encode the total colorcapacity.

• 256 (8-bit), 1024 (10-bit), 4096 (12-bit) brightness levels in eachprimary color.

• Bit-depth specifies the range of A-D converters that convert the leveldetected by the scanner’s CCD sensors into digital signals.

• 8 bit to 24 bit color means the computer can display 256 to 16.7million different hues

Features of Scanners

Dynamic Range

• The maximum image density that the scanner can handle.

• D-max indicates how dense an image can be before the scanner can nolonger distinguish the light shining through it.

• Any part of an image that’s more dense than the scanner’s D-maxrating, 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 lightthat’s diminished by a factor of more than 10000.

Features of Scanners

D-max

• 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 toresolve - hardware resolution.

• Interpolated resolution – control software of the scanner computesadditional dots in between those that are actually scanned, and thuspushes 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 inthe scan and makes lines looks smoother.

Features of Scanners

Resolution

• 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

Light Sources

Features of Scanners

Optical Character Recognition

• OCR software can convert into word processor, data base orspreadsheet files.

• Matrix matching – small parts of each bit image it scanned is comparedto 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 sizeand shape of the character matrix.

• A matrix-matching OCR system must have either an enormous libraryof bit patterns or the system must be limited to matching a fewtypestyles and fonts.

Feature matching – analyze each bit pattern that is scanned.

• It derives the essential features of the character from the pattern ofbits – an up slope, a peak, and a down slope. In that every letter hasthe 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.

Features of Scanners

• Primarily used for OCR applications• Automatically runs each sheet of a multiple page document

through a scanner.

Sheet Feeders

Interfacing

• 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.

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.

Electrical Interfacing

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.

Application Interfacing

Conclusion

1. what format you want (black & white, grayscale or color)

2. the resolution

3. preliminary scan is made to define the image area and dynamicrange.

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.

Before scanning any image consider:

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 Laserprinter . (M.Imp)

3. Write short notes on printers & scanners.

Thank You