Method to use Grid Sag into the system

  • 5 October 2020
  • 3 replies
  • 409 views
K

Hi everyone,


Can you guys help me.


I think to use Grid Sag as the method to import wavefront aberration in my optical system in advance. I had made some practical into my system using the Grid sag but I have 2 problems that I would like to ask and learn. I had attached the file below.


Firstly, I had imported some Dat file(in Zemax/Objects/Grid Files) to use as my grid sag in my system, but only ‘ Random_Grid_Minus` has been shown in the surface sag analyzing data. I want to ask, if you guys know why it happen?


Secondly, when I imported the `Random_Grid_Minus` into my system, I cannot see any change happen in the image that I analyzed. For example, I analyze the data in the spot diagram before I import the grid sag and after I import the grid sag. Why there is no any change in the data? Can anyone help me?


Maybe there is something that I did not realized or maybe I don’t have the right knowledge about it.  I would love to know and learn.


Thank you.

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3 replies

S
Rank
Userlevel 6
Badge +2

Hi


By only 'Random_Grid_Minus' has been shown in the surface sag analyzing data, do you mean that the other .dat files do not appear? You can refresh the list by clicking on 'Update File Listings'. You can also try closing and reopening OpticStudio. If they still don't show, there might be an issue with the files themselves. 



 


Regarding to 'Random_Grid_Minus', we can see the sag looking at Analyze...Surface...Surface Sag:


 


As you can see, this is the sag added to your system. 


But the Grid Sag surface is a dummy surface, by this I mean that before this surface, the material is AIR and after this surface the material is AIR. So no matter the geometry of this surface, it will not have any impact on rays.


So maybe what you are looking for is the Grid Phase surface? The Grid Phase surface will add phase to your rays and the gradient of the phase will bend rays. So you could convert the grid sag surface into radians. One wave is 2π radians.


Also have a look at the size of your grid. It seems too small.


Let us know if you have any further questions.


Sandrine


 

Sandrine Auriol
K

Thank you for your response Miss Sandrine.


I have some problem to convert Grid sag into the Grid phase. Does it have the same format as the Grid sag? Can Ms Sandrine or anyone help me to give some example for the format on how to change the grid phase into the dat file that can read by the zemax. 


Next, is it important to put material on the grid sag like n-bk7 or mirror? I try not to use any material which is the surface is air, but the result at the analyze data is not change. it will only change if i use material like n-bk7 on my grid sag. 


My plan is to import the wavefront aberration data that i get from experiment into my system in zemax at infront of the lens, it means the wavefront is at the air state. It is possible to use any grid phase or grid sag in air surface? or do you guys have any idea or any example that i can look at so that i can import my data into the system based on above condition. 


Thank you.

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Csilla Timar-Fulep
Rank
Userlevel 5
Badge +2

Hello,


Thanks for your follow up question here!


The Grid Phase surface is nearly identical to the Grid Sag surface. The key differences are:



  • The units of sag are radians of phase instead of units of length.

  • The unitflag data is only used to scale the delx, dely, and derivative values.

  • The surface shape is a plane.

  • A diffraction order is supported. The diffraction order is a multiplier on the phase values. A value of zero will turn 'off' the phase effects. Setting the order to -1 will reverse the sign of all defined phase values.

  • A 'shear distance' is supported.


You may find more information about the Grid Phase file format in the Help file at:

The Setup Tab > Editors Group (Setup Tab) > Lens Data Editor > Sequential Surfaces (lens data editor) > Grid Phase


Further reference about the required .DAT file format and about the construction of the Grid Sag files can be found at:

The Setup Tab > Editors Group (Setup Tab) > Lens Data Editor > Sequential Surfaces (lens data editor) > Grid Sag


You may find example .DAT files in the \Zemax\Objects\Grid Files folder. To check that the .DAT file has been imported correctly, please use the the Analyze…Surface…Phase analysis tool.


As Sandrine suggested, please have a look at the size of your gird. Currently, it looks too small:



You may find more information about Grid Sag file generation and usage in the following knowledgebase aricles. You may use the Grid Phase surface very similarly:


How to use the Grid Sag surface type


How to write a Grid Sag DAT file programmatically


If you have further questions, please let us know and we will be happy to help!


Best,


Csilla

Csilla Timar-Fulep

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