Research at the Precision Engineering Center
The Ultramill EVAM tool has been used to machine millimeter-scale optical surfaces. Simple spherical reflectors were made first to evaluate the types and sources of surface errors which can occur when making optical parts of this size. Several spherical surfaces were machined and errors removed on successive parts, reducing the figure error to 62 nm RMS. Next a fiber-optic beam splitter was designed which features high-sag off-axis ellipsoidal reflecting surfaces to be machined using the Ultramill. This beam splitter eliminates additional refracting elements, such as ball lenses, used for collimation in existing designs. A test reflector was made with sculpted 3-D geometry representative of that required by the beam splitter. Initial performance test and metrology results are presented for this reflector. As a preliminary to the optical surface experiments, thermal stability of the Ultramill was investigated for the original open-circulation cooling arrangement as well as for a closed-circulation scheme. Closed-circulation cooling is determined to have considerably greater temperature stability leading to reduction in form error caused by thermal variations. However pressure pulsations from the existing diaphragm-type coolant circulation pump limit the achievable surface roughness to 20 nm RMS when using closed-circulation cooling.
The following faculty, students, and PEC affiliates are involved in this project:
| Faculty | Students | Affiliates |
| Thomas A. Dow | David Brehl | National Science Foundation |
