I think you can search it in US Patent Website address if it still available. I think last time I got it from Lynn Farmer's website. Canon did actually the one who invented ring type piezotronic motor for autofocus lens actuator (maybe after adapting Shinsei Kyogo invention). I think they hold the ring type piezotronic motor worldwide patent, Nikon AFS using ring type piezotronic motor like in Canon's USM lenses (refer to Canon and Nikon website).
Pardon me, I tried to search for it but I can't get the address again.