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Canon patent to avoid AF hunting through improved detection of AF errors

AF hunting

Canon patent for a method to avoid Auto-Focus hunting by improving the detection of AF errors. If I got it right, this is achieved by using a linear polarizer between the optics and the imaging sensor (any help appreciated). This should improve the detection of inconsistent AF measurements and hence reduce if not drop the so called “AF hunting”. According to the machine-translated patent literature, this is…

a technology that can detect the displacement direction and amount of focus without having to drive the focus group.


  • Patent Publication No. 2016-24391
    • Published 2016.2.8
    • Filing date 2014.7.23
  • Example 1
    • Zoom ratio 1.00
    • Focal length 293.46
    • F-number 2.93
    • Half angle of view (degrees) 4.22
    • Image height 21.63
    • Overall length of the lens 274.0
    • BF 59.13
  • Canon patent
    • When placed near squeezed retarder phase difference changes toward the periphery from the center, and a linearly polarized light having a vertical plane of vibration, the focus position of the direct polarized light having a horizontal oscillation plane deviates
    • Place the linear polarizer between the optical system and the imaging device, and polarization selection means
[via Egami]


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