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Laser printers theory

Laser printers as well as LED printers rely on one and the same technology used at first in photocopying machines. This process is known as electrophotography and was invented in 1938 and developed by Xerox and Canon in the later 1980s. Electrophotographic process in laser printers, involves six basic steps: A photosensitive surface (photoconductor) is uniformly charged with static electricity by a corona discharge. Then the charged photoconductor is exposed to an optical image through light to discharge it selectively and forms a latent or invisible image.
 
 

Development is done by spreading toner, a fine powder, over the surface, which adheres only to the charged areas, thereby making the latent image visible. At the next step an electrostatic field transfers the developed image from the photosensitive surface to a sheet of paper. Then the transferred image is fixed permanently to the paper, by fusing the toner with pressure and heat. The last step is cleaning of all excess toner and electrostatic charges from the photoconductor to make it ready for next cycle.
Laser printers as well as LED printers offer the best print quality i.e. the highest resolution. The unique difference is the method of exposition or formation of the latent image.
Laser printer scanning assembly:
Laser printers rely on a laser beam and scanner assembly to form a latent image on the photo-conductor bit by bit. The scanning process is similar to electron beam scanning used in CRT. The laser beam modulated by electrical signals from the printer's controller is directed through a collimator lens onto a rotating polygon mirror (scanner), which reflects the laser beam. Then reflected from the scanner laser beam pass through a scanning lens system, which makes a number of corrections to it and scans on the photoconductor.
 
 
 

 
 
This technology is the major key for ensuring high precision in laser spot at the focal plane, accurate dot generation at a uniform pitch and therefore better printer's resolution.
Laser printer scanning process: the latent image creation
 
 
 
 
Laser printers as well as LED printers are the right solutions for applications demanding high quality with high-speed output of images and text data, such as desktop publishing.
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