PC Computer Hardwaee Output Devices Pt 3

Page Printer

These print complete page itself at a time as it done by Xerox like photocopying electrostatic process. These mat be
Laser Printer
Inkjet Printer

Electrostatic Printer

Photographic film Output

Laser Printer

Laser printer are non impact printer. They print one page at time . These printers use laser or other light to produce an image on a photo sensitive drum. The computer controls the laser beam to turn it on and off when it cut back and forth across the drum.
An image is produced on raster scan principal. The laser exposed area attract toner (an ink powder). Thereafter the drum transfer the toner to the paper . The paper then moves to a fusing station where toner is permanently fused on the paper with heat or pressure. After this the drum is discharged and cleaned. Now the drum is ready for processing the next information on the page.
Laser beam is the technology of transmitting powerful beam of light rays in a line without any reflection and refraction and loosing its power . The full form of laser is Light(frequency) Amplification of Stimulated Emission of Radiation.
The laser printers are quiet and they produce high quality output. These printer are expensive and require lots of maintenance. The low speed laser printer prints 10 page per minute or more these are used with microcomputer. High speed laser printers producing up to 300 page per minute are manufactured for mini and large computers . The laser printers have become popular for large printing work. They are used for desk top publishing work also.. the difference between Xerox machine and laser printer is that a Xerox machine the image of the original text is formed on the photosensitive drum with a camera lens whereas is laser printer image is formed by scanning laser beam using computer’ control. The computer sends the characters of a page of the text to be printed in the printer’s buffer memory.

Inkjet Printer

In inkjet printer system produces characters by spraying small ink droplets onto paper. A high frequency electrical generator causes a pyroelecttric crystal to vibrate and throws of tiny droplets supplied from a reservoir. T he droplets then charged by an electrode and guided by horizontal and vertical deflection plate in the precise manner to form the desired character on paper
The speed of the printers lies in the range of 40-300 pages. The average life of an inkjet printer head is about 10 million characters which is 5 times more than that of the print head of an impact type dot matrix printer. The inkjet printer uses ink cartridge containing a column of tiny separators . The print quality of these printer is very near to letter quality.

Electrostatic Printers
Printer of this type forms characters by impressing static charges of electricity on special paper. These charges attract a toner to the charged spots for coloration .The needles apply charges on the paper in a serial fashion.
These printers are capable of very fast speed , up to 20,000 lines per minute. A variety of alphabets , graphics and very large drawing can be produced in a very short times . These devices can draw better than a line plotter and even produced images similar to black and white photographs , with several hundred dots per square inch.

Photographic Film Outputs
These mean are used to store mass amount of data in a very small space . These are type
Micro film
Microfiche

Micro film
The output from computer instead being or pinted is displayed on high resolution CRT VDU. Then it is photographed on 16mm or 35 mm film. A camera is controlled to make films successive output pages on the screen of CRT. A special micro film reader is used to read the output. Some micro film readr also produce a hard copy using xerographic process. Another method is known as COM(Computer Output on Microfilm/ Microfiche). In this first computer’s output is recorded on to magnetic tape which is then fed into a machine called MICROFORM READER. It reads the magnetic tape and copies the data obn to microforms. The copied data can be inspected by using a viwer which projects the copied information on to a screen . Full size copies can be printed.

Microfiche is a sheet of film of size 100 mm x 75 mm on which information worth 80 pages can be recorded . The advantage of using microfiche is that it records information at the rate of 1 milion character per minute and that too in a small space Microfiche is generally used to record display catalogues, archieval documents.