Effects Of Mirror Surface Ripple On Image Quality

Mirror surface ripple acts as a phase grating to diffract light out of the central maximum of the point spread function (PSF), reducing image quality. The effects of ripple on image quality are examined with the aid of computer simulations using rotationally symmetric wavefront error models, and through interferometric measurements of a mirror known to have significant surface ripple. Image quality is evaluated in terms related to the performance requirements of large orbital astronomical telescopes that must perform in both ultra-violet and visible light. Techniques for measuring and specifying ripple are discussed.