Measurement of a highly freeform surface using a cylindrical null-screen

We propose a method to design the null-screen on a cylindrical surface when the surface under test is a freeform, this implies that the surface is described by a complex analytical expression. Also, the method avoids overlapping objects in the image plane this assures the appropriate correlation between the object and the image points. The surface under study was designed using Zernike polynomials and it was built through a 3D printer and CNC machine. To retrieve the surface sagitta, in previous work, we obtained the best-fitting surface using a probabilistic algorithm. In this work, we propose to measure the slopes of the test surface in the x and y directions, and by integration, we calculated the sagitta of the test surface. We present a comparison between both methods to show which of them recovers the shape of the surface more accurately.