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Canon Patent Application: Diffractive Optics Patent
We've uncovered many diffractive optics patents over the years, and while perhaps it wasn't the lenses we were all looking for, it's certain now that Canon's improvements in DO elements produced the ultra inexpensive 600 and 800mm F11 telephotos.
This patent application is a method of manufacturing of a DO element that suppresses short wavelength light.
In Canon's own words:
To provide a diffractive optical element having excellent image quality while suppressing the influence of scattering in a short wavelength region. SOLUTION: A close-contact two-layer diffractive optical element having a base material, a first resin layer having a diffraction grating shape composed of a plurality of concentric rings on the base material, and a second resin layer laminated in this order. Therefore, a low transmittance portion whose transmittance is lowered is provided at a position not including at least one lattice portion of the first resin layer and the second resin layer, and the internal transmittance of the low transmittance portion is the lattice portion. In comparison, it is characterized by being 2% or more and 6% or less lower at a wavelength of 400 nm.
Canon Patent Application 2020-170050
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