It just lifts a tip of the veil, but it's something.
It seems that at least early research were just attempts at copying German optics. Considering Japan was part of the Axis forces during WWII, it
might not be such a stretch to assume they simply adopted the German rayfilter assembly and used it in their own designs.
Of course, it's just a guess. Not even really an educated one at that.
I'm having fun digging stuff up. Always a lot of interesting stuff lurking beneath the surface.
