This paper presents the specifications, design, construction and evaluation of a piezo-driven tip/tilt/focus mechanism
which can align a detector or any other optical component in a cryogenic environment. Even with a no-adjustment design
philosophy, usually one or two components have to be adjusted in order to compensate for the total of optical and
mechanical tolerances in an optical cryogenic instrument. Normally these adjustments are made by means of shims or
stiff screw mechanisms and are applied at room temperature. In order to adjust the particular component(s), mostly by
just a few microns, the high-risk and time-consuming operation of opening a cryostat is required. For a large cryostat the
typical cycle of cooling, testing, warm-up, opening, adjustment, closing and cooling again, takes roughly two weeks.
Often the cycle needs to be repeated a few times before the required position is obtained. ASTRON developed a piezo
driven tip/tilt/focus mechanism which can adjust a detector or any other optical component in both the ambient and
cryogenic (<100 K, vacuum) environment. Only during adjustment the system is active, for the rest of time it is a passive
robust system with a high stability. The main specifications are a stroke of ± 0,6 mm and tip/tilt of ±1,2 mrad.