[Patent] Canon Patent For Improved Phase Detection Auto Focus

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

[via Egami]