Originally posted by RobA_Oz This lens has an image circle that would cover a 35 mm frame, which in itself is no proof that it is intended for such a body but is likewise no proof that it is not. Had it been less, then that would have been conclusive. It is also just a patent, so it isn't even evidence that such a design has actually been turned into a real (albeit proof of concept or prototype) lens.
The concave front element is interesting, though, even if it's been done before, just not often.
The patent was filed under Hoya. The idea that they would even invest resources in designing a lens with a 43mm image circle is interesting. If you never plan on making a FF then why invest the resources? Ricoh may have scrapped the idea, but at the time this was filed Pentax was investing in glass for a FF.