[Patent] Canon Files Patent For 600mm f/5.6 and 800mm f/5.6

Egami (machine translated) found a patent filed by Canon for a 600mm and a 800mm f/5.6 lens using diffractive optical elements.

• Patent Publication No. 2012-123152
  • 2012.6.28 Release Date
  • 2010.12.8 filing date
• Example 1
  • Focal length f = 584.99mm
  • Fno. 5.80
  • Half angle of 2.12 deg.
  • Image height 21.64mm
  • Length 360.03mm
  • BF 94.84mm
  • 17 pieces in 10 groups Lens Construction
  • 3 UD glass sheet
  • One fluorite
  • A surface diffraction plane
• Example 3
  • Focal length f = 779.00mm
  • Fno. 5.80
  • Half angle of 1.59 deg.
  • Image height 21.64mm
  • Length 462.02mm
  • BF 120.29mm
  • 17 pieces in 10 groups Lens Construction
  • 2 UD glass sheet
  • Two fluorite
  • A surface diffraction plane
• Low dispersion material with anomalous partial dispersion
  • To be effective in the correction of chromatic aberration
  • Specific gravity is large (heavy)
    • 3.18 fluorite
    • FK01 3.63
    • The specific gravity of small anomalous partial dispersion glass material
      • FK5 2.46
      • BK7 2.52
  • Surface may be damaged easily
  • FK01 is fragile due to temperature changes and large diameter
• Diffractive optical element (DOE)
  • To be effective in the correction of chromatic aberration
  • Is generated by unwanted light flare and ghosting
• Canon’s patented
  • Become positive from negative to DOE
  • DOE to place the position is hard to unwanted light incident