The mirror also independently pivots under {HEAD ~ the bias} of a spring about {TAIL ~ the mirror pivot axis} to an erected operative position wherein its upper and lower parallel edges are disposed perpendicular to the optical axis of the lens 
The mirror also independently pivots under { HEAD ~ the bias } of a spring about { TAIL ~ the mirror pivot axis } to an erected operative position wherein its upper and lower parallel edges are disposed perpendicular to the optical axis of the lens
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH