Three identical, custom made, heterodyne interferometers measure the translations of the sample table assembly relative to the stationary reference mirror. The beam layout of these double-pass differential plane mirror interferometers (DPMI's) is given in figure 1.

A polarizing beamsplitter divides the incoming two-frequency laser beam into a reference beam and a measurement beam. Each beam is then reflected twice by its respective mirror before being recombined and coupled into a fiber-optic detector. Beamsplitters and wave plates separate the first and second pass.

figure 1:schematic beam layout figure 2: interferometer optics with box for
mounting on Nanostage3D
and fiber-optic pickup
The optical length of the measurement beam and the reference beam are identical for maximum thermal stability. The DPMI measures only the relative translations along the mirror normal, this measurement is not influenced by other movements of the mirror or movements of the interferometer itself.

The overall dimensions of the DPMI optics are 58 x 48 x 10 mm (figure 2).

When used with Zygo® ZMI4004 measurement electronics the resolution is 0.15 nm.

The interferometer is available as a separate product. Please use the contact details on the right of this page if you want to learn more about the possibilities.


back to overview interferometers mirrors beam delivery sampleholder straight guides actuation