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

600mm f/5.6 DO

800mm f/5.6 DO

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
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