How can I cut the optical system of three mirror anastigmat (TMA) telescope by half in Zemax? 

  • 24 January 2023
  • 3 replies

Hi all,

I would like to ask how can we cut the system by half? For example, we have a three mirror anastigmat (TMA) reflective telescope system, and it is for on-axis design. Please see the example picture below. Now I would like to convert it to a off-axis design, I think the easiest starting point could be scaling up the system by a factor of 2, and then cut the system by half along the optical axis, so that the off-axis TMA geometry can be obtained. But I don’t know how to process the cutting in Zemax or if anyone has a better way to convert on-axis to off-axis?

I also attached a Zemax file for Hubble telescope made by 2 on-axis mirrors for anyone if want to show me the example to cut the system by half along the optical axis?

Thank you so much guys!


-- Kaden



Best answer by Mike.Jones 24 January 2023, 23:52

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3 replies

Userlevel 3

You can set a shifted aperture so only half of the system will be used. But I am not sure that it is good starting point for off-axis design,

Userlevel 5
Badge +3

Put the stop at the primary mirror surface and use a decentered smaller aperture to limit the light as desired.  Use decentered apertures on the secondary and tertiary mirrors as well.  There will be an intermediate pupil image between the secondary and tertiary, or tertiary and image, depending on the design.  That is a perfect place to put another aperture, decentered and tilted to match the tilt of the pupil image.  The pupil image aperture can serve as the aperture stop if needed.

Userlevel 5
Badge +3

Hi Kaden, an article I found useful when I learned off-axis system. FYI~

Demystifying the off-axis parabolic mirror – Knowledgebase (