Surface gradient integrated profiler for x-ray and EUV optics: self calibration method of measured position for an off-axis parabolic mirror (f=150mm) measurement

Y. Higashi; K. Endo; T. Kume; K. Enami; J. Uchikoshi; K. Ueno; Y. Mori

doi:10.1117/12.735973

20 September 2007 Surface gradient integrated profiler for x-ray and EUV optics: self calibration method of measured position for an off-axis parabolic mirror (f=150mm) measurement

Y. Higashi, K. Endo, T. Kume, K. Enami, J. Uchikoshi, K. Ueno, Y. Mori

Author Affiliations +

Proceedings Volume 6704, Advances in Metrology for X-Ray and EUV Optics II; 67040D (2007) https://doi.org/10.1117/12.735973
Event: Optical Engineering + Applications, 2007, San Diego, California, United States

Abstract

A new ultra-precision profiler has been developed in order to measure such as asymmetric and aspheric profiles. In the present study, the normal vectors at each points on the surface are determined by the reflected light beam goes back exactly on the same path as the incident beam. The surface gradients at each point are calculated from the normal vector and the surface profile is obtained by integrating the gradient. The measuring instrument was designed according to the above principle of the measuring method. In the design, four ultra-precision goniometers were applied to the adjustment of the light axis for the normal vector measurement. In the measuring instrument, the angle-positioning resolution and accuracy of each goniometer are respectively 1.8x10^-8rad and 2x10^-7rad. A coaxial with an off-axis parabolic mirror has been developing for applying as an optical cavity. The most important engineering technique is to measure the profile of the reflective surface with sub nanometer. The present measuring instrument is evaluating to have capability to the surface measuring accuracy with nanometer for such parabolic mirror profile measurement. A coaxial off-axis parabolic mirror with 150 mm focal length has been polished. The outside and inside diameter of the mirror is 360 mm and 258 mm respectively. The thickness of the coaxial direction is 50 mm. The focal point is located on the center of the coaxial and the center of the coaxial direction of the mirror. The profile measurement such a mirror has been demonstrated. Specially, self calibration method for increasing the measured position accuracy from measured data is discussed.

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Y. Higashi, K. Endo, T. Kume, K. Enami, J. Uchikoshi, K. Ueno, and Y. Mori "Surface gradient integrated profiler for x-ray and EUV optics: self calibration method of measured position for an off-axis parabolic mirror (f=150mm) measurement", Proc. SPIE 6704, Advances in Metrology for X-Ray and EUV Optics II, 67040D (20 September 2007); https://doi.org/10.1117/12.735973

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