{
  "patent_number": "US 5726435",
  "country": "US",
  "title": "How the QR Code Works",
  "original_title": "Optically readable two-dimensional code and method and apparatus using the same",
  "summary": "The 1995 patent by Toyota Central R&D Labs that invented the QR code, using three distinct corner squares with a unique 1:1:3:1:1 pixel ratio to let scanners instantly find and read the code from any angle.",
  "what_it_does": "The patent describes a square two-dimensional barcode containing data cells and three specific positioning symbols at its corners. These positioning symbols consist of concentric black and white squares. When a scanner draws a line through the center of any of these symbols at any angle, it always detects a specific pattern of dark and light widths in a 1:1:3:1:1 ratio. The scanner uses this unique ratio to locate the boundaries and rotational angle of the code. It then uses alternating light and dark timing cells to align its reading grid and decode the data stored in the remaining cells.",
  "what_it_does_not_cover": [
    "Does not cover standard one-dimensional barcodes that only store data along a single horizontal axis.",
    "Does not cover two-dimensional codes that use circular or hexagonal grid layouts instead of a square matrix.",
    "Does not cover codes that rely on color variations rather than binary dark and light cells to store data.",
    "Does not cover codes that lack the specific 1:1:3:1:1 ratio positioning symbols at three corners."
  ],
  "filed": "1995-03-14",
  "granted": "1998-03-10",
  "expires": "2015-03-14",
  "status": "expired",
  "holder": "Toyota Central R&D Labs Inc",
  "holder_url": "https://patentbrief.org/company/toyota-central-rd-labs-inc",
  "inventors": [
    {
      "name": "Masahiro Hara",
      "url": "https://patentbrief.org/inventor/masahiro-hara"
    },
    {
      "name": "Motoaki Watabe",
      "url": "https://patentbrief.org/inventor/motoaki-watabe"
    },
    {
      "name": "Tadao Nojiri",
      "url": "https://patentbrief.org/inventor/tadao-nojiri"
    },
    {
      "name": "Takayuki Nagaya",
      "url": "https://patentbrief.org/inventor/takayuki-nagaya"
    },
    {
      "name": "Yuji Uchiyama",
      "url": "https://patentbrief.org/inventor/yuji-uchiyama"
    }
  ],
  "times_cited": 250,
  "tags": [
    "consumer_electronics",
    "software",
    "automotive",
    "ecommerce"
  ],
  "abstract": "A two-dimensional code 1 consists of three positioning symbols 2, a data region 3, timing cells 4 and an apex detecting cell 5. The shape of the whole code 1 is a square having the same number of vertical and lateral cells. A scanning line passing through the center of each positioning symbols 2 always gives a constant frequency component ratio--dark:light:dark:light:dark=1:1:3:1:1, irrespective of the scanning direction. For this reason, even if a rotational angle of the two-dimensional code is not certain, the specific frequency component ratio of each positioning symbol 2 can be easily detected by executing only one scanning operation in a predetermined direction. Hence, the coordinates of the center of each positioning symbols 2 can be easily found. Thus, the position of the two-dimensional code 1 is quickly identified.",
  "url": "https://patentbrief.org/patent/us/5726435/qr-code-two-dimensional-barcode",
  "markdown_url": "https://patentbrief.org/patent/us/5726435/qr-code-two-dimensional-barcode/md",
  "google_patents_url": "https://patents.google.com/patent/US5726435",
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}