Canon Patent To Reduce Ghosting And Flaring (14mm f/2.8)

14mm f/2.8

Once more great Japanese site Egami (translated) spotted an important Canon patent. It is about the reduction of ghosting through anti-reflective coating on both sides of the lens, the coating consisting of fine uneven structures. Ghosting happens for instance when you point your lens at a bright light source, like the sun, and are the result of an acute angle of light bouncing (reflecting) between the individual glass elements of the lens. The technology is filed using a 14mm f/2.8 lens as engineering example. Should work well on other wide angle lenses too.

Surface coating

  • Patent Publication No. 2012-159720
    • 2012.8.23 Release Date
    • 2011.2.1 filing date
  • Example 1
    • F = 14.3mm focal length
    • Fno. = 2.89
    • Half angle of view ω = 56.5deg.
    • 14 images in 10 groups lens configuration
    • 1 UD glass sheet
  • Canon patent
    • Suppress the occurrence of the ghost
    • Having two surface anti-reflection surface of fine uneven structure
      • Non-periodic pitch
      • 400nm 300nm pitch less than average
    • Incident light for various interference conditions to cancel the reflected light is maintained
    • The average height of uneven surface with two different
    • 0.001% or less (2) the product of the reflectance of the surface (incident angle 0 degree)
    • 0.1% or less (2) the product of the reflectance of the surface (incident angle 60 degrees)
    • 0.05% more than the absolute value of the difference between the reflectance of the surface (2), (0 ° angle of incidence)
    • 0.2% or more the absolute value of the difference in reflectance of the surface (2), (incident angle 60 degrees)
    • The anti-reflection film of aluminum and aluminum oxide



[via Egami]

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