Low-cost refracting-reflecting athermalizing medium wave infrared lens

The invention provides a low-cost refracting-reflecting athermalizing medium wave infrared lens and aims at providing a low-cost refracting-reflecting optical lens which is small in aspherical mirror number, low in cost, made of a small amount of aspherical lenses and conventional silicon and germanium optical materials at a 3.7-4.8 [mu]m medium-wave infrared band and having the optical passive athermalizing performance. The technical scheme is that parallel light enters a main reflection spherical mirror (3) to form a converged light beam through a spherical cover (2) in an incidence mode, a convergence angle is decreased through a Mangin refracting-reflecting mirror (4), a primary mirror face (5) is formed by decreasing a part of aberration and increasing a part of balanced aberration and negative thermal difference of a lens to be arranged behind, the light beam is changed into divergent light, the divergent light enters a negative lens (6) made of an aspherical germanium material and a positive meniscus l