Three mutually orthogonal interferometers measure the relative movements of the sample. The moving target for the interferometers is a monolithic mirror which mirror-normals coincide with the measurement probe position on the 3D stage (figure 1). The reference mirror has a similar shape (figure 2). Aligning the mirror surfaces of the reference mirror and measurement mirror minimizes the deadpath error.

figure 1: measurement mirror. Mirror normals
intersect at the measurement point
figure 2: bottom view of the reference and
the measurement mirror
The orthogonality of the translation measurement system is determined by the squareness of the measurement and reference mirrors. To maximize this orthogonality, the monolithic measurement mirror is cut from a cube. The orthogonality of this cube, which sides form the reflective surfaces of the mirror, is calibrated accurately. The reference mirror is produced in a similar way.

Both mirrors are made from zerodur®, their thermal centers of expansion coincide with the probe position for optimal thermal stability.

back to overview interferometers mirrors beam delivery sampleholder straight guides actuation