The manufacture of modern optical components requires the use of high performance interferometers, usually based on phase-shifting techniques. However, there is currently no commercial phase-shifting interferometer having the capacity to measure large parts, such as those found in Inertial Confinement Fusion Lasers (NIF and Méga-Joule), and other large systems. Standard interferometers lack the simultaneous qualities of accuracy and spatial resolution required for the measurement of such components. Indeed, it has been shown that surface ripples with wavelengths of around 1 to 10 millimeters are extremely dangerous for large ICF optics, even at low amplitude, because of the process of non-linear ripple amplification present in high power laser systems. In order to circumvent the restrictions on size and performance of standard interferometers, we have designed and built a scanning interferometer, using a standard "small" diameter phase shifting interferometer. A PC computer is used to control the measurement process, acquire the interferograms and stitch the measurements together to produce the original large surface. The measurement sequence is completely automated. The advantages ofthis technique are low cost, small size, and no loss ofspatial resolution. One system has been in actual use for the characterization of large size mirrors (approx. 400 x 600 mm) since december 1994. In this presentation, we shall look over the design of the system, produce actual measurements, and discuss the technical implications of the stitching process in relation to specifications such as those currently being derived for ICF large components. This work is supported by CEA/CEL-V, as part of the Laser MégaJoule Program.

Date Published: 8 December 1997
PDF: 8 pages
Proc. SPIE 3047, Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference, (8 December 1997); doi: 10.1117/12.294276

Published in SPIE Proceedings Vol. 3047:
Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference
Michel L. Andre, Editor(s)