How can he "invent" this? Hasn't it been known for years? It's the same principle as two mirrors at right angles, only instead of a corner, there is a gentle be

How can he "invent" this? Hasn't it been known for years? It's the same principle as two mirrors at right angles, only instead of a corner, there is a gentle bend. I'm pretty sure I read about this in George Gamow's "One, Two, Three... Infinity".