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[Patent] Canon Patent For Improved Phase Detection Auto Focus

Phase Detection AF

Egami (machine translated) found a patent by Canon regarding an improved Phase Detection Auto Focus. Such a “hybrid” autofocusing system has been featured on the Rebel T4i/650D and the recently announced EOS M. The patented technology aims at improving speed and accuracy. Is this the AF system that Canon will implement on its next, more pro-oriented mirrorless camera, expected to be announced later this year?

  • Patent Publication No. 2010-60771
    • 2010.3.18 Release Date
    • 2008.9.3 filing date
  • Existing techniques
    • Patent Publication No. H11-281878
    • Different lengths of baseline using the AF sensor
      • F2.8 sensor: high focusing accuracy
      • Can detect a wide range of defocus amount (the amount of deviation of focus): F5.6 sensor
      • After roughly at F5.6 sensor is focused, making focus F2.8 sensor with high accuracy
    • Drawback
      • Depending on the timing F2.8 sensor is not used, focusing accuracy is not good
  • Canon’s patent
    • Different lengths of baseline using the AF sensor
      • Because of the defocus amount detection range is limited, must search as duplicate detection range
      • By using the F5.6 sensor, within a limit not exceeding the amount of defocus, it is possible to focus lens is driven at high speed
    • If the Live View
      • The image plane using phase difference AF
      • Focus lens is driven at high speed
        • Using the central pixel: When low-intensity
        • Using the neighboring pixels: When high-intensity
Imaging surface phase detection AF
[via Egami]
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