I've been wondering where the patent was that covers the new 400mm DO lens, this appears to be it. It describes the new process for the DO elements, and the first, third, and 4th examples are for a 400mm f/4 DO lens. I can't tell for sure if or which design was used in the 400mm DO, but the process for forming the diffraction elements is the same as Canon described in their description of the technology.
Given the popularity of the 400 DO, I'd expect that every possible effort is going into making the 600.
The patent describes a Prime lens, but the optical formula describes a Zoom Element as well as a single lens element . They seem to be covering the possibility of a zoom DO lens even though the patent is for Primes.
"zoom-lens-group data
Group ** side Focal distance Lens constitution length Forward side principal point position . Rear side principal point position
1 1 144.55 66.44. -29.74 -
60.942 19 -94.08. 7.47 6.24
1.973 22 991.13. 52.46 332.98 439.52. "
"Single lens data
lens ** side The focal distance
1. 1
476.272 3
614.583. 4
610.894 8
155.415. 9 -
254.116 13
287.497. 15 -
144.698 19 -
33.959. 20
48.9810 23
42.9811.
24 -62.6912 26 -31.
1713 27 28.2714 29
-29.9615 32 32.8416
33 -33.9717 35 -71
.0018 36 54.0619 38
128.8920 40 0.00"
This is a excerpt describing the bonded diffraction gratings and how the two are brought together to function as a single element that corrects many issues with the earlier DO lens.
"In 2 lamination-type diffraction optical element 1 shown in Fig.10 (a), the first diffraction grating 6 is formed with first ultraviolet curing resin on the glass substrate 4, and the second diffraction grating 7 is formed on other glass substrates 5 with different second ultraviolet curing resin from first ultraviolet curing resin. On both sides of the air layer 8 of the interval D, close arrangement of these [ 1st ] and the second diffraction gratings 6 and 7 is carried out, and they function as one diffraction optical element with the combination of these two diffraction gratings 6 and 7. "
Examples 1, 3, 4
a focal distance of 400 mm, and an optical system for the super telephoto lenses of Fno4.0.
Examples 2 is for a 600mm f/4 which is a bigger brother to the 400mm DO similar to example 1.
The optical systems of the working example 2 shown in Fig.3 are a focal distance of 600 mm, and an optical system for the super telephoto lenses of Fno4.0. Like the working example 1, front side lens group LF has positive refracting power, and rear side lens group LR also has positive refracting power. The diffraction optical element Ldoe and the aspheric surface Asph are provided by the same position as the working example 1. The diffracting plane of the diffraction optical element Ldoe as well as the working example 1 has positive refracting power.
