Patent: New Diffractive Optic Patents

More DO Lenses?
A few patents in regards to diffractive optics have come about. 70-300 f/4.5-5.6 DO IS, 14 f/2.8 DO and a 600 f/4 DO IS.
Diffractive optic patents keep coming up, though no new products are being announced. It does appear Canon is invested in the technology and thinks there is a market for it. I am a big fan of the 400 DO and hope to see longer DO lenses in the future.
Read more about the patents after the break.

Patent Publication No. 2012-78397

• 2012.4.19 Release Date
• 2010.9.30 filing date

Example 1

• Zoom ratio 4.01
• 135.50 – - 290.90mm 72.50 focal length
• Fno 4.66 -. 4.97 – 5.87
• 9.07 – - 4.25deg 16.62 a half angle of view.
• Image height 21.64mm
• 171.47 – - 204.08mm 144.08 full-length lens
• BF 40.08mm
• 18 sheets 12 group lens configuration
• 3 UD glass sheet
• A plane diffraction
• Seven-group zoom positive and negative positive positive and negative polarity
• Inner Focus (Group 6)
• Shake correction (group 2)

Example 2

• Zoom ratio 2.84
• 200.00 – - 292.50mm 103.00 focal length
• Fno 4.67 -. 5.44 – 5.77
• 6.17 – - 4.23deg 11.86 a half angle of view.
• Image height 21.64mm
• 189.12 – - 210.66mm 162.16 full-length lens
• BF 45.16 – 58.25 – 70.16mm
• 13 pieces in 11 groups Lens Construction
• 2 UD glass sheet
• A plane diffraction
• Five-group zoom of positive and negative positive positive and negative
• Rear focus

Example 3

• 14.36mm focal length
• Fno. 2.89
• 56.38deg half angle of view.
• Image height 21.60mm
• Length 133.66mm lens
• BF 38.47mm
• 16 pieces in 10 groups Lens Construction
• 2 UD glass sheet
• Two surface diffraction
• Two positive lens group a negative
• (Part of the front group) Inner Focus

Example 4

• 584.94mm focal length
• Fno. 4.12
• 2.12deg half angle of view.
• Image height 21.64mm
• Length 404.06mm lens
• BF 123.32mm
• 18 sheets 12 group lens configuration
• 3 UD glass sheet
• One fluorite
• Two groups of positive-positive lens
• (Part of the front group) Inner Focus

Conventional diffractive optical element

• Because there is a thick diffraction grating, and obliquely incident light, the diffraction efficiency is reduced
• When the diffraction efficiency is reduced, flare, ghost, imaging performance deterioration, such as contrast degradation occurs

Canon’s patent

• Can be in close contact with another medium to a diffraction grating, to reduce the thickness
• Capable of suppressing a decrease in diffraction efficiency
• With another medium, and fine particle dispersion ultraviolet curing resin material