Laser printers use the property of static electricity in an innovative way. The core part of a laser printer is a rotating photo receptor drum or cylinder, which is made of highly photo conductive material. The corona wire shown in the figure carries electricity which induces positive charge in the drum surface. When a laser beam is fired on the surface of the drum, the the point where the beam is fired, gets negatively changed. The laser beam is controlled by a print controller ( a processor inside the printer ) which determines how to move the laser so that it 'writes' an image of -ve changes on the +vely charged surface (this is called 'electro-static' image). Next step is to draw images on the cylinder with toner - Toner is a fine, black powder which is positively charged. As the drum surface comes under toner hopper, the toner glues to the negative charged 'electro static' image on the drum, but not to the positively charged "background."
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. Now the paper has the required image drawn with fine toner powder which is required to get etched permanently. The fuser ( see fig B ) heats the paper to melt the toner and make a permanent impression. As the paper moves fast, the paper does not get burnt.
The dischage lamp (fig A) neutralizes all the charges on the surface of the drum so that above steps can be repeated for the next scanline.
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. Now the paper has the required image drawn with fine toner powder which is required to get etched permanently. The fuser ( see fig B ) heats the paper to melt the toner and make a permanent impression. As the paper moves fast, the paper does not get burnt.
The dischage lamp (fig A) neutralizes all the charges on the surface of the drum so that above steps can be repeated for the next scanline.
1 comment:
Now that was cool... I just forgot about the toner when I asked that day about printer.. Hmm... so thats the guy who gives the color.. Thats cool.. the explanation was cool.. When is the Subprime write-up coming?
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