Optical Metrology

Located within the Instrumentation Division, the Optical Metrology lab (OML) has been actively involved in the improvement of the quality of optical components in use at synchrotron radiation beamlines throughout the world. Established in 1983, the OML has pioneered the use of non-contact optical profiling instruments to measure the surface figure and surface roughness on large aspheric mirrors used to reflect x-rays at extreme grazing incidence angles. A collaboration with Dr. Eugene L. Church from Picatinny Arsenal, Dover, NJ, has resulted in an improved understanding of the fundamental nature of surface roughness in terms of fractal geometry and in comprehensive models of instrument performance.

The activities of the OML divide into three basic areas:

• Surface roughness investigations, using a Micromap Promap 512 optical profiler (upgraded from a WYKO NCP-1000 instrument) and with a Digital Instruments Stand-Alone Atomic Force Microscope.
• Surface figure measurement, using the Long Trace Profiler designed and built in this laboratory, to characterize the absolute shape of large flats, spheres and aspheric optics.
• Design and fabrication of the all-silicon SuperStep structure as a calibration standard for both surface profiling and scattered light measuring instruments.

Current Long Trace Profiler (LTP) installation in Optical Metrology Lab. A 1 meter long Si cylindrical mirror is shown under the test. The "open architecture" optics board allows for rapid prototyping and testing of various external and internal components.