Klaus,
I have been reading up a lot! Insects have s great capability of perceiving specific degrees of rotation or spiral continuous rotation, separately from color! That is amazing!
They use it to get flight orientation and to break down camouflage of predators and prey as well as for sexual signaling.
It seems to me that this is so important for you and I think you could get around some of the cost issue by using surplus optics that the army over orders and they have forgotten why they authorized that research in the first place. If I was a funding organization, which sadly I am not, I would unhesitatingly fund you acquiring the needed equipment!!
Anyway I am sorry we ourselves cannot use this modality with our own eyes as it would give a lot of new information.
Asher