2 moment elliptical bending with trapezoidal shaped mirrors for near perfect bending.
High accuracy homing and repeatability.
Various motor and control options.
Ultra-high vacuum, high vacuum, low vacuum and helium variants.
Low cost of ownership.
Easy mirror coating maintenance.
The IDT Small KB Mirror is based on a well established approach of dynamically figuring
the mirror shape by applying two adjustable moments to a trapezoidal shaped mirror.
By correctly tapering the longitudinal width of the mirror and applying a linear
moment distribution a nearly perfect approximation to the ideal focusing ellipse
can be achieved. The slope errors from bending are negligible, well under 0.1μrad
(typically <0.05µrad) and the mirror surface given a properly designed bender can
be formed to nearly perfect ellipses.
Successful dynamically figured optics requires bending mechanics that are capable
of precisely applying a linear moment distribution without causing residual distortions
or drifts in time due to temperature variations and system relaxations. The IDT
Small KB Mirror bender is designed to apply only the minimum force necessary to achieve
the required figure resulting in maximum useful mirror length and avoiding distortions
caused by benders that clamped to the mirror. The bender is designed to utilise
mirrors with simple shapes that are easy to install and capable of accepting a range
of mirror thicknesses and tapers. This approach reduces the cost for manufacturing
the mirrors and provides rapid flexibility so that a single system can be reconfigured
to optimally provide focusing for a wide range of experiments.
The upstream and downstream moments are applied through the use of a crossed arm
arrangement where the forces applied to the lever arms are achieved by pushing off
the back surface of the mirror on opposite ends. This results in a closed loop force
system that insulates the mirrors figure from external thermo-mechanical variations
in the support mechanism. The lever arms are parallel to the length of the mirror
and the applied actuator forces are perpendicular to the lever arms effectively de-coupling
thermal expansion effects of the lever arms from the applied moment. The lever arms
couple to each end of the mirror through a pair of leaf springs and inner and outer
bending bars. The leaf springs de-amplify thermo-mechanical drifts of the crossed
arms and actuators and allow the mirror contacts to conform to the natural shape
of the mirror, keeping residual contact stresses to a minimum.
The moments are controlled with two stepper motor and gear head combinations. The
actuators utilise a scissor jack arrangement that results in a constant stepper motor
torque as a function of bending moment keeping the systems drive friction independent
of radius of curvature and allowing fine figure adjustability at high bending load.
The actuators are capable of adjusting figure to one part in 104 of the final curvature
which is sufficient to achieve figure errors under 0.1μm.
* developed by IDT with a grant from the North West Development Agency
Technical Data
