{
  "patent_number": "US 3867571",
  "country": "US",
  "title": "How Laser Printers Use Rotating Mirrors to Write Information",
  "original_title": "Flying spot scanner",
  "summary": "A 1972 Xerox patent describing how to use a spinning mirror to scan a laser beam across a page, adjusting the speed of the data to keep the image sharp.",
  "what_it_does": "This system uses a laser to project a tiny, high-intensity spot of light onto a light-sensitive surface, like a drum in a printer. A multifaceted rotating polygon mirror reflects this beam, sweeping it across the surface to create a line of information. Because the beam moves faster in the middle of a scan than at the edges, the system uses a function generator to speed up or slow down the data transmission rate (the bit rate) to match the spot's velocity. This ensures the printed image remains uniform and does not look stretched or distorted.",
  "what_it_does_not_cover": [
    "Does not cover non-laser light sources that lack collimated, uniform intensity.",
    "Does not cover scanning systems that use a fixed data rate regardless of the spot's velocity.",
    "Does not cover systems that lack a multifaceted rotating polygon for beam deflection.",
    "Does not cover digital image processing or software-based image correction."
  ],
  "filed": "1972-11-27",
  "granted": "1975-02-18",
  "expires": "1992-11-27",
  "status": "expired",
  "holder": "Xerox Corp",
  "holder_url": "https://patentbrief.org/company/xerox-corp",
  "inventors": [
    {
      "name": "David E Damouth",
      "url": "https://patentbrief.org/inventor/david-e-damouth"
    },
    {
      "name": "Gary K Starkweather",
      "url": "https://patentbrief.org/inventor/gary-k-starkweather"
    }
  ],
  "times_cited": 22,
  "tags": [
    "consumer_electronics",
    "mechanical",
    "semiconductors"
  ],
  "abstract": "A flying spot scanning system is provided by utilizing reflected light from a multifaceted rotating polygon which is then directed to the scanned medium. A light source illuminates at least one of the facets of the polygon during each scanning cycle to provide the spot scan. In each scanning cycle, information is transmitted to scanned medium by modulating the light from the light source in accordance with a video signal. To assure a uniform spot size at the scanned medium, an optical convolution of elements is selected in combination with the light source such that an adequate depth of focus at the medium is assured. An imaging lens is provided in series with a lens, which expands an original light beam, to converge the expanded beam to illuminate the selected facet or contiguous facets that are to control the movement of a spot throughout a scan angle. In the preferred embodiment, the rotation of the polygon is synchronized in phased relation to the scan rate used to obtain the video signal.",
  "url": "https://patentbrief.org/patent/us/3867571/laser-printer-starkweather",
  "markdown_url": "https://patentbrief.org/patent/us/3867571/laser-printer-starkweather/md",
  "google_patents_url": "https://patents.google.com/patent/US3867571",
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}