Infrared instruments are generally operated at cryogenic temperature which causes a serious problem for the mounting of optical components. This is specially the case for complex dioptric systems where the optical quality is strongly dependant from the relative centering of the lenses. In the frame of the pre-design of the VLT high resolution and large field infrared imager (HAWK-I) a design using spring system has been intensively tested. The paper describes the test carried out in order to assess the thermal and mechanical behavior of the mount. A special technique has been used to accurately verify the conservation of the lens position from room temperature to cryogenic temperature.