Ray tracing of focussing using ellipses and parabolas
These animations show the ray optics of three different profiles. The first is of the reflection of a source placed at one of the foci of an ellipse, resulting in its image at the position of the other foci. The second shows the ray focussing of parallel radiation incident on the inside of a parabolic surface, also resulting in a perfect focus (ignoring diffraction effects). The last is of the focussing of parallel radiation passing through a plano-parabolic lens, such as in modern compound refractive lens elements. Note that the focal position depends very slightly on the position of the incident beam relative to the central axis, resulting in some aberrations. This is extremely small in the hard x-ray regime.