laser printer
A laser printer belongs to the group of page printers and works according to the method of electrophotography. In the laser printer, the page to be printed is converted by a Raster Image Processor( RIP) into a raster image that can be printed by the laser printer. In electrophotography, the image to be printed is transferred by a laser beam or by a line oflight-emitting diodes to a light-sensitive image drum made of semiconductor material.
To expose the image drum, the laser beam is deflected line by line via rotating mirrors. In the case of LED lines, there is a light-emitting diode for each pixel. Before the charge image is applied to the image drum, the surface is electrically charged. Subsequent exposure to the laser beam causes the charge to flow off at the points exposed by the laser beam. These areas become electrically neutral. A charge image is formed on the image drum, which is coated with the electrically charged toner particles.
The toner is repelled from the electrically charged areas of the charge image and adheres only to the areas that are not electrically charged, i.e., the areas exposed by the laser beam. A toner charge image is thus formed on the reproduction device and transferred to the paper, which is also electrically charged; but with opposite polarity. The toner image is fixed to the paper by the fuser unit. This is located at the end of the paper pass and is designed to fuse the toner to the paper. The fuser unit consists of a heated pair of rollers that burn the toner powder into the paper at about 200 °C.
Laser printers cannot vary the intensity of the individual printing dots. In addition, color laser printers cannot mix the different colored toners well. Therefore, a pixel can only accept the paper color or one of the primary colorscyan, magenta and yellow as well as black. All other colors must be created via halftoning.
Laser printers are characterized by high resolution, which can reach up to 2,400 dpi, and a printing speed of over 100 pages per minute, pages per minute( PPM). Handling is relatively simple, and the devices work reliably.
Laser printers are available as high- performance printers and workstation printers, as black-and-white and as color laser printers.