Abstract: A flexure-ring is provided for centering a lens in a bore of a housing with 3N lens contacting stubs, where N is an integer equal to or greater than one. The stubs are formed by increasing the inside diameter of the ring made to fit tightly around a lens except at 3N locations for the aforesaid stubs, and said ring having an outside diameter made to fit tightly inside the housing bore locations. Behind each stub, a segment of the ring is removed down to a chord perpendicular to a ring diameter passing through the center of each stub. That chord is selected to have a length greater than the lens contacting surface of the stub, thereby to produce a reduced cross section of the ring on both sides of the stub to serve as flexures in relieving stresses due to different coefficients of thermal expansion of the three parts involved due to changes in temperature while in use.