Canon Patent For New 14mm f/2.8 With Improved Surface Coating

Egami found a patent filed by Canon for a 14mm f/2.8 lens with a new anti-reflective coating, Subwavelength Structure Coating. This method optimizes the refractive index and allows for a thinner anti-reflective film. Looks like Canon is working on a successor of the EF 14mm f/2.8L II USM lens. You can read the translated article here.

Patent specification (machine translated):

• Patent Publication No. 2013-47780
  • 2013.3.7 Release Date
  • Filing date 2011.7.26
• Example
  • F = 14.3mm focal length
  • Half angle ω = 56.6 °
  • Fno. 2.89
  • 14 images in 10 groups lens configuration
• Canon patent
  • Antireflection film which is excellent in productivity and reflectance characteristics
  • The refractive index of the substrate (original surface of the lens) is 1.65 to 2.20
  • Consists of three layers, the ratio of the refractive index change with a three-layer
  • The third layer
    • Average roughness of less than 400nm pitch structure
    • By continuously varying the ratio of the space-filling structure uneven, changing the refractive index
    • After drying, the film is immersed in hot water and applied to the second layer solution (containing aluminum oxide) by spin coating, plate-like crystals deposited on the surface
  • If spin coating of the wet process, excellent in productivity can be realized a uniform thickness
  • Little change in the characteristics even if there is variation in thickness