Nanoradian Surface Profilers (NSPs) are required for state-of-the-art synchrotron radiation optics and high-precision optical measurements. Nano-radian accuracy must be maintained in the large-angle test range. However, the beams' notable lateral motions during tests of most operating profilers, combined with the insufficiencies of their optical components, generate significant errors of∼1 μrad rms in the measurements. The solution to nano-radian accuracy for the new generation of surface

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... ers in this range is to apply a scanning optical head, combined with nontilted reference beam. I describe here my comparison of different scan modes and discuss some test results.