OpticsTalk: Deep Dive into Creating the Wavefront, Spot Diagram, PSF, and MTF in OpticStudio

  • 19 May 2020
  • 9 replies
  • 447 views

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Here's the discussion space for the OpticsTalk: Deep Dive into Creating the Wavefront from the Spot Diagram, PSF from the Wavefront and MTF from the PSF, to hosted by OpticStudio Optical Test Engineer, Michael Humphreys.


Join Michael to discuss the principles of how OpticStudio calculates Wavefront, PSF, and MTF. 


Have questions? Post them here before the talk!


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Slides and code from the talk will be posted soon!


 

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Slides and code from the talk here.

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Why there is a difference between manual calculated MTF and Zemax data? 

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Hi Andrey,


When you say a difference between manually-calculated MTF and OpticStudio-computed MTF, what specific OpticStudio MTF analysis are you referring to? Do you have a model that you can share along with the computation that you were manually performing (as in, was it the code provided here in this forum thread? some modification to that code that you did?)? And, what is the magnitude of difference you are seeing between the two data sets you are comparing?


I'm just asking for some more specific information to better help you, as I want to make sure we're addressing the correct reasons here!


Thanks, and I'm looking forward to hearing back from you!


~ Angel

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Hi Angel.


I've used the sample from this topic just increased the sample size for wavefront and MTF calculations. The absolute difference in MTF is about 0.01 for tangential (saggital values are quite close).

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Hi Andrey,


Thanks for your follow-up here! Appreciate the clarification.


I've actually reached out to Michael to provide some more background information, and essentially, the difference boils down as follows:


Basically, the OpticsTalk was a general 'proof-of-concept' presentation/discussion, and the manual approach was a very basic scaling of data to get it into the proper format for the MTF results (as we go from Wavefront to PSF to MTF, for instance). To get into the additional steps/considerations and the mathematics behind it (a Wavefront Map that is physically non-circular, for example) would be to divulge proprietary information, so I cannot really comment on that front. In addition, since each step in the computation depends on the data obtained in the previous analysis, we could expect this manual approach to diverge a bit more with subsequent analyses that relied on this MTF data.


I hope this clears things up for you -- please let us know if you have further questions. Thanks!


~ Angel

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Hi Angel,


Thank you for the information.

Hi, thanks for all.


I would like to know if is it possible to know a little more about the scale of the psf we can find with the code. I would like to use the psf to create a simulation of an image through my lens (as image simulation in Zemax) but a don't know what scale i have to use for the psf. Is it the scale according to the detector? And how can i change the scale computed from the code with a new one according to the detector? thanks

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Hi Antonin,


I would recommend checking out the Help System page for the Image Simulation. 


Specifically:



  • A 'grid' of Point Spread Functions (PSFs) are computed. The grid spans the field size, and describes the aberrations at selected points in the field of view defined by the bitmap and field size settings. The PSF grid also includes the effects of polarization and relative illumination.

  • The PSF grid is interpolated for every pixel in the modified source bitmap. At each pixel, the effective PSFis convolved with the modified source bitmap to determine the aberrated bitmap image.

  • The resulting image bitmap is then scaled and stretched to account for the detected image pixel size, geometric distortion, and lateral color aberrations.


If you want to recreate the image simulation, you will not necessarily want to scale the PSF according to the detector, but take multiple PSF measurements at different field points.


Let me know if this helps or you have any other questions.


-Kaleb

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