William Folberth patented the sight window in 1933. He had something like 110 patents, including the windshield wiper. He and C.N. Hickman were likely the two most prolific inventors among archers. Hickman invented the Bazooka, spark chronograph and a lot of archery related stuff. You can read his biography in Clarence N. Hickman, The Father of Scientific Archery, by Maryanne Schumm.
If I can figure how to post pictures here(!), I will include some of one of Folberth's first sight window bows, used to develop his patent.