what the units are for the ZERN value in the merit function?

  • 8 January 2021
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Q: What the units are for the ZERN value in the merit fucntion. Is it system units, microns, waves, fringes or something else ?


Ans: The unit of Zernike Fringe coefficients is same as Wavefront Map, which is waves.The following is an example of a calculation


1.First open the built-in Double Gauss 28 degree field.zmx. Then check Zernike Fringe Coefficients for Field 3.

 


2.Then copy these value in Excel. In excel, built X and Y mesh and calculate the wavefront manually following the equation. As you can see below. The value is same as that you can find in the Wavefront Map. I didn’t make any change to the coefficients in the test, so I think the unit used in Zernike Fringe should be same as that in Wavefront Map. Since in Wavefront Map it’s unit is “waves”, I think this is same for the Zernike Fringe. I have also calculated P-V, which is also very similar to that reported in Wavefront Map. I think the difference is mainly about the fitting and sampling.


As can be seen from the above examples, the unit of Zernike Fringe coefficients is waves.The excel file for the calculation is shown in the attachment.


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