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LASER PRINTER

LASER PRINTER 

    Laser printers uses static electricity to make a pattern of letter /figures on a photosensitive drum(which is charged positive all over) and thereby makes a negative charged figure/image on the drum. The positive charged toner get slicked on the drum due to opposite charges as per patterns which
requires to be written on the paper and finally get dropped on the more strongly charged(positive)paper and then fused permanently by applying heat on the paper and that is how laser jet works. We will try to understand this basic concept with the help of diagram 
 
The image formation system consist of 6 stages in a laser printer 
1. Cleaning(by discharge lamp) 
2. Charging(by corona wire or roller) 
3. Writing (by laser light) 
4. Development( by toner getting glued with drum) 
5. Image transfer on paper 
6. Fusion (by fuser on paper by heating)

Working of Laser printer 
The drum is given a total positive charge by the charge corona wire, a wire with an electrical current running through it. (Some printers use a charged roller instead of a corona wire, but the principle is the same.) As the drum revolves, the printer shines a tiny laser beam across the surface to discharge certain points. In this way, the laser "draws" the letters and images to be printed as a pattern of electrical charges -- an electrostatic image. The system can also work with the charges reversed - that is, a positive electrostatic image on a negative background. 

    After the pattern is set, the printer coats the drum with positively charged toner- a fine, black powder. Since it has a positive charge, the toner clings to the negative discharged areas of the drum, but not to the positively charged "background." This is something like writing on a soda can with glue and then rolling it over some flour: The flour only sticks to the glue-coated part of the can, so you end up with a message written in powder. 

    With the powder pattern affixed, the drum rolls over a sheet of paper, which is moving along a belt below. Before the paper rolls under the drum, it is given a negative charge by the transfer corona wire (charged roller). This charge is stronger than the negative charge of the electrostatic image, so the paper can pull the toner powder away. Since it is moving at the same speed as the drum, the paper picks up the image pattern exactly. To keep the paper from clinging to the drum, it is discharged by the detac corona wire immediately after picking up the toner. 

    Finally, the printer passes the paper through the fuser, a pair of heated rollers. As the paper passes through these rollers, the loose toner powder melts, fusing with the fibers in the paper. The fuser rolls the paper to the output tray, and you have your finished page. The fuser also heats up the paper itself, of course, which is why pages are always hot when they come out of a laser printer or photocopier.

The main features of laser jet printer are as follows:- 
1. Memory-8 to 16 MB RAM 
2. Fast printing speed i.e. more number of pages per minute 
3. Network printing that is printer will not be connected with any computer but will be directly connected with the switch and will work for all computers in the network. 
4. Works as printer, photo copier and scanner



अन्य विषय 
अन्य जानकारी

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