page_title: Laser printing
section_title: Cleaning and recharging
hierarchical_section_title: Laser printing / Printing process / Cleaning and recharging
caption_attribution_description: English: 1000x magnification of color laser printer output at 1200 DPI. 4 dots/pixels are in view, with the remaining blue toner particles contributing to the overall bluish hue of the portion of the image being magnified.
context_page_description: Laser printing is an electrostatic digital printing process. It produces high-quality text and graphics by repeatedly passing a laser beam back and forth over a negatively charged cylinder called a "drum" to define a differentially charged image. The drum then selectively collects electrically charged powdered ink, and transfers the image to paper, which is then heated in order to permanently fuse the text, imagery, or both, to the paper. As with digital photocopiers, laser printers employ a xerographic printing process. Laser printing differs from traditional xerography as implemented in analog photocopiers in that in the latter, the image is formed by reflecting light off an existing document onto the exposed drum.
  Invented at Xerox PARC in the 1970s, laser printers were introduced for the office and then home markets in subsequent years by IBM, Canon, Xerox, Apple, Hewlett-Packard and many others. Over the decades, quality and speed have increased as the price has fallen, and the once cutting-edge printing devices are now ubiquitous.
context_section_description: As the drum completes a revolution, it is exposed to an electrically neutral soft plastic blade that cleans any remaining toner from the photoreceptor drum and deposits it into a waste reservoir.  A charge roller then re-establishes a uniform negative charge on the surface of the now clean drum, readying it to be struck again by the laser.
caption: Magnification of color laser printer output, showing individual toner particles comprising 4 dots of an image with a bluish background
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