Hi @alice.renaux !

Thank you for posting on the forum.

• The coefficients are calculated at the exit pupil, because this is where we compute the wavefront. The wavefront reference is given here:

  

  Note that the coefficients consider a uniform sampling.
  If the surface is not the image plane, have a look at this section “Evaluating results at intermediate surfaces” of our help files.
• This will be automatic. When you disalign, the software will recompute the wavefront.
• Have a look at that article https://support.zemax.com/hc/en-us/articles/4406838460819-Modelling-of-a-Shack-Hartmann-Sensor-for-eye-aberration-evaluation.
  To find the exit pupil position, you can use a solve:

  

• For the Merit Function, where did you read that you need to compute the Zernike coefficients one order higher than the highest coefficient you need? I need to check this.

Hello,

Thank you very much for your answer, it is very clear !

• Concerning the number of Zernike coefficients to compute, I couldn’t find the page again but it was because in order to compute an accurate coefficient, Zemax has to compute the whole order of the coefficient or something (I don’t know if this is exact but it is what I understood).

• If I am manually disaligning an optical system, are the ZERN operands in the merit function computed in the same way as the Zernike Standard Coefficients computed in the Anlyze => Wavefront window ?

• And do I have to turn the Ray-Aiming feature on when disaligning an optical system on purpose ?

Again, thank you very much for your help !

Hi @alice.renaux !

• Yes the ZERN coefficients are computed in the same way. 
• The Zernike coefficients consider a uniform sampling so yes I would turn on ray-aiming. There is a post discussing this here: