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What is Laser Printer ? A high quality no impact printer that produces sharp, dark images Uses a rotating drum principle similar to that of a photocopier.

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Presentation on theme: "What is Laser Printer ? A high quality no impact printer that produces sharp, dark images Uses a rotating drum principle similar to that of a photocopier."— Presentation transcript:


2 What is Laser Printer ? A high quality no impact printer that produces sharp, dark images Uses a rotating drum principle similar to that of a photocopier Charging the corotron by the high-voltage power supply The major manufacturers: Canon, Hewlett Packard, NEC, Okidata, and Panasonic. History 1975 -- A demonstration unit by Canon 1984 -- introduced by Hewlett-Packard 1980s -- dot-matrix and laser printer were pre-dominant 1990s -- quickly became popular Advantages High printing quality Low toner consumption High printing speed Relatively low running costs Quietness Disadvantages High energy consumption

3 How laser printer work ? The same printing process as photocopiers Laser beam discharge the photoreceptor areas to create an electrostatic image (the page to be printed) Two different methods: “ Write-white “ -- the background areas are not to be printed “ Write-black “ -- the areas which will be printed Most printers are now write-black printers which are generally better at printing very fine lines Two MAIN components: Printer Controller Print Engine

4 The structural chat of Laser Printer

5 Printer Controller Dedicated computer Creates an image from commands Several tasks: Communication, Interpretation, Formatting, Rasterising Finally passing the image to the Print Engine

6 preparing an image for printing Communications Sending the document to be printed Receives data through a communications port Tells the computer when to stop or start sending data Job Spool Passes the data directly to the interpreter Store the data in a queue Reduces time in printing multiple copies of a document Interpretation Examines the data sent from the computer Identifies the command embedded in the data Implementing the printer control commands (perform generic operations) Translate the commands into a shorthand form -the formatter can process more efficiently Passes the structured print data to the formatter

7 Formatting Takes the structured print data Arranges the page Determined how much can be fitted on the line Converting vector graphics command to bitmaps Checking the validity of any bitmap graphics send to the printer Fonts Bitmap — store each letter as a pattern of dot Outline -- store each letter as a set of equations -- make the boundary of each letter Rasterising Receives and Converts the commands into an array of dots to be used Takes the bitmap for each character of text Places the text at the specified position in the array Overlays the array with any bitmap graphics

8 Print Engine Incorporates a small computer Control the motors and electrical circuits, Nothing on the scale of the printer controller Main Components : Laser Scanning Assembly, Photoreceptor, Toner Hopper, Developer Unit, Corotrons, Discharge Lamp, Fuser, Paper Transport, Paper Input Feeders and Paper Output Trays

9 The process to fix the toner onto the paper Laser Scanning Assembly It can be called Raster Output Scanner(ROS) Comprises the laser,a rotating mirror,and a lens Laser emits a very brief pulse of light for each dot to be printed No pulse for blank area The mirror deflect the laser beam in the horizontal axis to position the dot along the line The lens positioning of the beam to counteract the divergent effect The mirror deflect the laser in one axis,movement in the other axis is achieved by moving the photoreceptor Photoreceptor Normally a cylinder,or drum Having a very smooth surface - accept in electrostatic charge and is discharged by light Before exposure to the laser beam,it is charged evenly on the charger coroton A spot of discharged laser beam places on it A pattern of discharged dots was created

10 Toner Hopper Exist into hold toner Fine powder (black or colored) made of plastic granules -- attracted to electrostatic charged Forms image to paper Feeds toner into the developer unit Developer Unit A process of image generation on the photoreceptor by toner Magnetic roller covered in fine magnetic particles The magnetic particles act as a very fine "brush" As the roller rotates, it passes the toner hopper and the brush effect of the developer gathers a smooth coating of toner particles. The roller passes the photoreceptor The toner particles are attracted to the electrostatic charge on the photoreceptor They jump on to the charged areas of the photoreceptor surface Create a pattern in the image of the electrostatic charge produced by the laser.

11 Corotrons A wire Between corotron and photoreceptor there is the voltage in several kV shock air ionization (corona discharge) Ions are stored on the surface of a photoreceptor The high voltage intense electric field Result in the application of electrostatic charge Not friendly to the environment !! Can be divided into there type: Charger Corotron, Transfer Corotron, Detac Corotron Charger Corotron Charges the photoreceptor surface before it reaches the laser beam Ensure a smooth, even charge over all the photoreceptor surface Transfer Corotron Electrostatically charges the paper Attracts the toner on to the surface of the paper Detac Corotron Cancels the charge on the paper Prevent it from sticking to the photoreceptor or other papers

12 Discharge Lamp Exposes the whole width of the photoreceptor to light Remove the pattern of the image (written by the laser) Actually a line of L.E.Ds Fuser Fix the toner onto the paper WHY? The toner is a very fine plastic powder The plastic powder lies on the paper in a very thin coating Nothing to hold the toner in place The plastic powder can easily be brushed off, or even blown off, the paper Destroy the image that has been created. How to fix the toner to the paper permanently ? 1.heated 2.passing between a pair of very hot rollers (mechanism pressing) 3.the plastic melts around the fibers of the paper and is "fused" into place *smaller warming period & smaller energy consumption The printing process has been completed

13 Paper Transport Feeding the paper through the printer between motorized rollers For the movement of the photoreceptor and developer roller Paper Input Feeders Trays of paper(cassettes) is used The printer will obey commands from the computer Clearing deleting toner remainder from the photoreceptor after transference on paper



16 Typical Desktop Printer Paper Output Trays Receive the printed paper Two type of output trays: Face up tray Receives paper delivered printed side up Used for the manual feed facility e.g.card, transparencies Face down tray Receives paper face down Delivers the multi-page document in correct order The main output tray for normal printing Hold a large amount of printed output Paper Path Not a physical component of a printer Gives a straight paper path for feeding difficult materials

17 Manual Feed Facility Allows the user to insert difficult material e.g.card,label,transparencies…… Normally bypasses any band between the paper input feeder and the photoreceptor Sources Cheng Mei Yi (2) Lee Choi Lin (10) Lo Ka Ki (19)

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