Multi-pitch nano-accuracy surface profiler for strongly curved X-ray mirror metrology

•The MPNSP instrument development is introduced including the objective, the hardware design, the theory, and the details in the alignment of the test mirror surface to the pitch rotation axis.•By detecting the rotation axis of the mirror pitch with a machine vision approach, we can determine and then reduce the vertical distance between the pitch rotation axis and the test mirror surface to a sub-mm level.•We describe a practical data acquisition procedure for strongly curved X-ray mirrors with a total slope range larger than the slope measuring range of the autocollimator used in the instrument. This opens a path to measure extreme off-axis elliptical mirrors with the MPNSP technique.