Geometries of the close and wide solutions of a severely degenerate binary lensing event. Lensing parameters s and q are the projected separation and the mass ratio of the binary, respectively. The straight line with an arrow represents the source trajectory and the curve that varies with the source trajectory represents the trajectory of the image centroid. The solid and dotted curves represent the image centroid induced by the companion, m ₂, and primary, m ₁, respectively. The coordinates (ξ, η) represent the axes that are parallel with and normal to the binary axis. The coordinates for the close and wide binaries are centered at the center of mass and the midpoint of the binary lens, respectively. Here, all lengths in the close and wide binaries are normalized to the individual Einstein radii of two cases.