US Patent 9354444 Annular optical spacer and optical lens system

An annular optical spacer includes an outer annular surface, an inner annular surface, a first side surface, a second side surface and a plurality of protruding structures. The inner annular surface surrounds a central axis of the annular optical spacer and is opposite to the outer annular surface. The first side surface connects the outer annular surface with the inner annular surface. The second side surface connects the outer annular surface with the inner annular surface and is opposite to the first side surface. The protruding structures are regularly disposed on the inner annular surface. Each of the protruding structures extends along a direction from the first side surface to the second side surface and is integrated with the inner annular surface.