Computer generated holograms (CGH) can be used for testing a widespread range of aspheric surfaces with high accuracy. Different, holographic configuration can be used; for the information storage, photographic material is very often appropriate. Two beam interferometric arrangement in which both beams pass through the CGH is desirable in order to compensate inhomogenities of the hologram storage material. For symetrlcal optical systems to be tested, in-line(Gabor-Type) and off axis CGH are applied. Although we use both configurations we prefer often off-axis arrangements The implementation of the technique requires the analysis of errors due to the testing procedurs as well as to additional optical component in the beam to be analysed and the manufacturing of the OGH. Automatic fringe analysis is very useful and will be discussed. A two wavelength technique can be used to reduce the sensitivity.
