Image simulation - Mixed mode or Multiconfiguration


I am currently working on a telescope whose primary and secondary mirrors are divided into three segments. I would like to see how deviations in their position relative to each other affect the final image. 
Does anyone know what mode (Sequential and multiconfigurations or NSQ) is best to use for this analysis?

Thanks in advance for your help.




Best answer by Jeff.Wilde 23 May 2023, 08:14

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Hi Tomasz,


This is not my area of expertise, but I’d be tempted to stick with the sequential mode. My reasoning is that you’ll be forming an image and you’ll be needing some of the analyses that are available in Sequential mode, such as OPD or ray fan, and MTF or PSF. Also, it will be more efficient to trace the necessary rays in sequential mode as opposed to having to deal with many more rays (or the hassle of setting the rays individually) in non-sequential mode. More generally, if I can get away with sequential, I avoid non-sequential as much as possible.

Hope this helps and take care,



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I think the best approach depends on what exactly you would like to model.  If you just want to segment an otherwise continuous mirror surface, then you can use sequential mode with a user-defined aperture (UDA) for each segment.  The UDA’s can be moved around on the surface to see how changes in their relative locations alter the imaging performance.  If, however, you want to tip/tilt the individual segments or move them along the z-axis (piston motion), then a mixed-mode model is the way to go.  In this case the mirror and its segments are all defined in a non-sequential group that is embedded inside a sequential model.

Erin Elliot (at Zemax) gave a very nice webinar on how to use both of these techniques to simulate the James Webb telescope.  Here’s the link:  Modeling the James Webb Telescope segments in OpticStudio