Analytical study of disturbing diffraction orders in in-line computer generated holograms for aspheric testing

The effect of spurious diffraction orders due to an in-line diffractive compensator for the measurement of aspheric surfaces is analytically studied. The use of a filtering aperture to isolate the measurement diffraction order from the stray orders introduces additional spurious fields that must be analyzed for a correct evaluation of surface defects. In this work the influence of the additional diffraction orders is studied and an analytical expression for the disturbing field on the detector is obtained.