Hard Copy Devices

Hard copy dvices

There are two major categories of hard copy devices.
i)Printers
ii)Plotters

PRINTERS

Printers produce output by either impact or non-impact methods.Impact printers press formedcharacter faces aginst an inked ribbon onto thg paper. A line printer is an exapmle of impact device. Non-impact device printers and plotters use laser tecniques, inkjet sprays, Xerographic process, electrostatic methods and electro thermal methods to get images onto the paper.

Types of printers

*Dot matrix printer
*laser printer
*Inkjet printer
*The electrostatic printer
*The electro thermal printer

Dot matrix printer

It has a print head containing a rectangular array of protruding wire pins,with the number of pins depending in the quality of the printer.Individual characters or graphics patterns are obtained by retracting certain pins so that the remaining pins form the pattern to the printed.

Laser printer

Alaser beam creates a charge distribution on a rotating drrum coated with a photo electric material, such as selenium.Toner is applied to the drum an then transfered to paper.

Inkjet printer

It produces output by squirting the ink in horizontal row across a roll of paper wrapper on a drum.The electrically charged ink stream is deflected by an electric field to produce dot matrix patterns.

The electrostatic device

It places a negative charge on the paper,one complete row at a time along the legth of the paper.Then the paper is exposed to a toner.The toner is positively charged and so is attracted to the negatively charged ares, Where it adheres to produce the specified output.

The Electrothermal Device

This method uses heat in a dotmatrix print head to output patterns on heat sensitive paper.The printer of the invention permits high rate printing at a relatively low cost of supplies. With the ink ribbon omitted, printing can be effected directly on thermo-sensitive paper.A thermoplastic ink is transferred from a ribbon to the base medium (usually paper or transparent film) by localized heating. The heating occurs as current is passed from discrete electrical contacts on the print head through a resistive layer in the ribbon to a common return layer.

Plotters

A graphic printer that images with ink pens.It actually draws point to point lines directly from vector graphics files.The plotter was the first computer output device that could print graphics as well as accommodate full size engineering and architectural drawings.Using different colored pens, it was able to print in color long before ink jet printers beacme an alternative.

Pen plotters are still the most affordable printing device for CAD and other resolution unlike any other printer.The lines are not made up of dots .They are actually drawn providing infinite resolution.

Types of plotters

*Drum plotter
*Flatbed plotter
*Electrostatic plotter

Drum and Flatbed plotter

Both types of plotters actually “draw” the images.The drum plotter wraps the paper around a drum with pin feeds.It moves the paper back and forth for one direction of the plot.The pens moves across the paper, creating other axis.The bed of the flatbed unit determines the maximum size of the total drawing.In drum plotters the pen is moved in a single axis track and the paper itself moves on a cylindrical drum to add the other axis or dimension.

Types of Drum Plotter

*Inkjet
*Thermal
*LED

Flatbed plotter

A graphics plotter that contains a flat surface that the paper is placed on. The size of this surface (bed) determines the maximum size of the drawing. A graphics output device that draws by moving a pen in both horizontal and vertical directions over a sheet of paper; the overall size of the drawing is limited by the height and width of this bed. Plotter that uses a drum revolver to move the paper during printing while the actual pen performs the printing.

Drawing pens

Pen plotter use drawing pens that provide infinite resolution because the line are actually drawn. All other panting devices print dots. Pen plotters print by moving a pen or other instrument across the surface of a piece of paper. This means that plotters are restricted to line art, rather than raster graphics as with other printers

Author: Deepak Chahar

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