Several embodiment of an athermalizing apparatus is described. In one embodiment, the athermalizing apparatus includes a lens element and a support member coupled to the lens element. The support member has a sloped outer surface and a first coefficient of thermal expansion ("CTE"). The athermalizing apparatus further includes a rib member having a substantially complementary sloped surface that bears on the sloped outer surface of the support member. The rib member has a second CTE. The sloped outer surface of the support member forms a ramp angle with respect to an optical axis of the lens element. A radial expansion of the support and/or rib member causes an axial displacement of the support member as a function of the ramp angle.