Translation for front mission 2 iso5/18/2023 ![]() Only residual local stresses in the glass arises around the bond spots. The leaf springs decouple thermal expansion of the component in the lateral direction. Usually, the thermal center is located on the optical axis. Because of the flexures, the thermal expansion difference between component and mount can be large without significant effects. If a temperature difference occurs between component and mount, the center of expansion is at Tc. The arrangement of the leaf springs determines the location of the thermal center. This is beneficial for the stability of the component under inertial loads (such as gravity). The natural frequencies of the mount are high because each degree of freedom of the optical component is constrained with high stiffness. Isostatic arrangement of three leaf springs around a component, showing the location of the thermal center. Wave front errors introduced by these parasitical forces must be checked by hand calculations or FEM analysis. In practice true kinematic constrains do not exist and bending moments due to parasitic stiffnesses can have a second order influence. Because of the isostatic design the mount cannot impose significant forces or bending moments on the optics and deform the optical component. By arranging three leaf springs around the optical component as shown in figure 3, the optical component is constrained once in each degree of freedom. Because a bond spot has high shear stiffness, but a low torsional stiffness the combination of bond spot with a leaf spring only constrains X and Y with high stiffness. ![]() A leaf spring constrains X, Y and RZ with high stiffness (in the local coordinate system in figure 2). An isostatic design means that each degree of freedom is constrained only once. Alternatively it can be manufactured using wire EDM.Ī rigid optical component has 6 degrees of freedom (DOF). The leaf spring can be manufactured with conventional inexpensive milling. When properly dimensioned, the tensile and lateral stiffness are much higher than the bending stiffness (as a rule of thumb a ratio of 1:1000 is achievable). Examples are given which are supported by analysis and test results. In this paper, a simple and predictable design approach is demonstrated which shows excellent stability and low WFE while it is still capable of surviving severe loads.
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