A solar image or spectrum scanning technique

An image or spectrum focal plane scanning technique is described in which the output beam is displaced but undeviated relative to the input beam. Additionally, the focus is constant, introduced polarization is less than 0.7%, and one form permits rapid scanning over an image 90 mm in size. Performance in terms of linearity and jitter is given. The need for rapid scan methods in solar spectrophotometry follows from observations in the solar continuum light, which show, at low scanning frequencies (f), excess fluctuations over the expected shot noise. This excess noise increases proportionally to 1/f for f < ~ 10 Hz.