High-precision rolling angle measurement for a three-dimensional collimator.

We propose a precise rolling angle measurement for a collimator to extend its application in 3D angular deformation measurement, with performance significantly superior to that of the traditional 2D technique. The rolling angle measurement is realized by taking full advantage of the point array image, which is projected in terms of the collimated beam. The measurement error is estimated according to the proposed algorithm. The characteristics of the point array are analyzed to optimize the point array for precise measurement, including the point distribution, the point array resolution, and the point array area. Both simulations and experiments demonstrate that subarcsecond precision rolling angle measurement is achieved by our method, which is superior to those attained by other proposed targets.