Nanometer precision in large surface profilometry

摘要

The Long Trace Profiler (LTP) is in use at many synchrotron radiation (SR)211u001elaboratories throughout the world and by a number of manufacturers who specialize 211u001ein fabricating grazing incidence mirrors for SR and x-ray telescope applications. 211u001eRecent improvements in the design and operation of the LTP system have reduced 211u001ethe statistical error in slope profile measurement to the 1 standard deviation 211u001elevel of 0.3 microradian for 0.5 meter long mirrors. This corresponds to a height 211u001eerror on the order of 10-20 nanometers. This level of performance allows one to 211u001emeasure with confidence the absolute shape of large cylindrical aspheres and 211u001espheres that have kilometer radii of curvature in the axial direction. The LTP is 211u001eversatile enough to make measurements of a mirror in the face up, sideways, and 211u001eface down configurations. We will illustrate the versatility of the current 211u001eversion of the instrument, the LTP II, and present results from two new versions 211u001eof the instrument: the in situ LTP (ISLTP) and the Vertical Scan LTP (VSLTP). 211u001eBoth of them are based on the penta prism LTP (ppLTP) principle that utilizes a 211u001estationary optical head and moving penta prism. The ISLTP is designed to measure 211u001ethe distortion of high heat load mirrors during actual operation in SR beam 211u001elines. The VSLTP is designed to measure the complete 3-dimensional shape of x-ray 211u001etelescope cylinder mirrors and mandrels in a vertical configuration. Scans are 211u001edone both in the axial direction and in the azimuthal direction.