Hartmann mask

A Hartmann mask is an optical device used to analyze the quality of lenses and mirrors in telescopes and other optical systems. It consists of a series of small holes or slits arranged in a grid pattern. When light passes through the mask, it creates a pattern of spots or lines on a detector. By examining this pattern, technicians can assess how well the optical system focuses light, detecting any imperfections or misalignments. This tool is essential for improving and calibrating optical instruments to ensure they produce clear and accurate images.