Measurement of errors by axial misalignment and tilt of the null screen used in experimental arrangements by deflectometry

To measure the quality of optical surfaces, one of the most used methods is the deflectometry. To implement this technique, a screen is used to choose some incident rays on the surface under test. Subsequently, the intersection of the rays is measured, after having passed through the surface, in a detection plane perpendicular to the optical axis. With the coordinates of the points in the detection plane, the normal vectors are determined in each point of the surface under test. The process is simple if the incident rays are chosen in a configuration called null, that is, in the detection plane the measured points will be distributed in a uniform configuration, rectangular, circular, radial, etc. In this work we present the numerical simulations, considering an incident spherical wavefront in the null screen that is placed at an arbitrary position between the source and the flat surface of an aspheric lens that was used in the experimental arrangement. In the simulations it is expected to obtain a uniformly distributed arrangement of spots, which will be compared with the experimental results.