Electronic Interface With Vignetting Effect Reduction for a Nikon 6B/6D Autocollimator

In this paper, we present an electronic interface created for the Nikon 6B/6D visual autocollimator that allows for an increase in the final resolution of measurements and a reduction in the vignetting and distortion effects produced by this optical instrument´s lenses. The electronic interface consists of a Basler ACE high-definition camera and its positioning devices and a computer with a subpixel digital image processing package. The latter includes two main procedures: one for scale calibration and the other for determining the position of crosshair lines. Both procedures work at subpixel level. The feasibility of the measurement method was verified. The resolution obtained for the measurement of angular displacements is about 0.019 s of arc, 25 times better than the one registered by the original visual system. Its overall performance was compared against an electronic level with internationally traceable certification.