Canon Patent Application: Air Sphere Coating and Flourine being combined
In this patent application, we see Canon combining two coatings to form one coating that would benefit lenses, and allow for greater control of flare and ghosting while at the same time, assist with cleaning the front element and keeping it clean.
ASC or Air Sphere Coating has been around since the Canon 100-400L II was released, and Flourine coatings have been implemented in many of Canon's L lenses to date.
A low-refractive-index layer utilizing gaps between particles has a problem that oily matter penetrates and diffuses into voids between particles in the film. The present inventor has found that the contamination that has not been visually recognized at the time of adhesion of the contamination and low-molecular-weight oily matter generated by the adhesion of contaminants diffuse among particles in the low-refractive-index layer to decrease the refractive index, resulting in deterioration in the appearance to a degree that can be visually recognized.
I would not be surprised to see this technology implemented in some of Canon's higher end L lenses at a future date and time.
US Patent Application 20180148603
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