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I have measured the surface deviations of a 16mm diameter lens with a Zygo running on MetroPro and have exported a 37 term Zernike Fringe Sag data table. When I enter the Zernike Fringe Sag coefficients directly into OpticStudio the magnitude of the resulting transmitted wavefront error is appropriate to the expectation based on the surface error but the Normalization Radius was left defaulted to 100 in OpticStudio and was not set to match any corresponding radius value in MetroPro. If the Norm. Radius is changed the resulting wavefront changes but not in any way that makes sense with regards to the Zygo measurements or expectation.



Is there a method to set the Normalization Radius in OpticStudio such that Zernike Fringe Sag data imported from MetroPro can be correctly used to model an as-built lens? Could the MetroPro output also assume a Normalization Radius of 100?

Hi Jonathan,



When you update the Normalization Radius, what are you changing it to? We typically recommend matching it to the Semi-Diameter value of your lens. I am not too familiar with MetroPro, but it looks like their manual follows the same convention:



 





 



Also - are you sure the Zernike data you are given in MetroPro is sag data? Or is it wavefront data? Based on the manual, it looks like it may be wavefront data. If so, you will need to convert to sag deformation by using wavelength as a scale. This is because the Zernike terms of the Zernike Fringe Sag surface in OpticStudio are in lens units (typically mm) whereas wavefront data will be in waves. 



Best,



Allie

Hi Allie,



I would like to use also the MetroPro data to simulate the tested lens. If the tested lens have a semi diameter of 20, so the normalized radius has to be 20 also?



Also, for this tested lens , do i have to put the radius, conic constant or just the zernike are sufficient to describe the lens? (May you have an exemple for that.)



Best regards,



Christophe

Hi Christophe,



Yes, if your lens has a semi-diameter = 20 mm, then generally we recommend setting the normalization radius = 20mm.  This means that at the semi-diameter of the part the normalized radial coordinate = 1.



For the second question, I'd confirm with MetroPro if Zernike data from Metro is whole surface deformation data or pure surface irregularity data (which means surface data subtract reference sphere already). If it’s pure irregularity data, when you model the surface, you will need to define  the radius and other parameter data to add reference sphere, and then the zernike terms to model irregularity.

Hello Berta,

I have a set of 37 Zernike coefficients that I need to input into Zemax for my project. However, I'm unsure about the correct procedure for reflective surfaces (mirror). Should I divide each coefficient by 2 and then multiply by the wavelength?

Additionally, I have chosen to use the Zernike standard sag for this application. Is this the right approach? I also noticed that the peak-to-valley (PV) value in my wavefront map differs from the measurement obtained from Zygo.

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