HI:
In a wavefront measurement by ZYGO GPI interferometer the Piston and Tilts were checked (in a dialog box) to be removed. ZYGO then generates the Zernike coefficients for the number of Zernike terms selected (in this case 16 terms were selected).
Question:
Are these generated Zernikes supposed to fit the wavefront with its piston and tilts removed? If so, all the pistons and tilt terms in the generated Zernikes should add up to zero or close to zero. But this is not the case, I added up piston terms and that's not zero, similarly tilt terms don't add up to zero.
ZEMAX program removes piston and tilts when generating Zernikes, here when piston terms and tilt terms of the generated zernikes are added each comes to zero.
Appreciate your comments and explanation.
thanks,
Djamshid