What is CGH mapping and how does it get corrected?

In a CGH test of surface figure, rays must arrive normal to the test optic surface. Equally spaced rays normal to a test optic surface are not necessarily equally spaced on the CGH.

In the example below, an aspheric test optic with a circular aperture maps to an elliptical and keystone-distorted footprint on the CGH.

Typically the more aspheric and the larger the CGH-test optic distance, the worse mapping distortion is.

Mapping distortion can be corrected using a polynomial mapping equation.

When mapping distortion is corrected, the surface deviation map represents equally spaced points on a plane at the UUT vertex, and surface deviation is in the direction of the UUT surface normal.

Mapping distortion is automatically corrected using Morpheus™, a software solution from AOM.