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Specifying size and location of exit pupil

Question

How can I control the size and location of the Exit Pupil in my optical system?

Synopsis

Specifying the size and location of the exit pupil

Solution

The Exit Pupil is the paraxial image of the Aperture Stop in image space. The optics between the Aperture Stop and Image Surface perform this imaging function. In order to change the location and size of the Exit Pupil, your Aperture Stop size and position must change. The optics between the system Aperture Stop and the Image Surface must already be designed appropriately to accommodate the imaging of the Exit Pupil to the desired size and location. If this is not the case, please refer to the following Knowledge Base item: Specifying size and location of exit pupil during optimization Assuming that your system meets the requirements cited above (that the optics between your Aperture Stop and Image Surface will readily accommodate the position of the Exit Pupil that you desire), then the approach to follow is to temporarily place the Aperture Stop at the desired location of your Exit Pupil, determine the proper location of the Aperture Stop and Re-Assign the Aperture Stop to that position:
  1. Place an extra surface just before the Image Surface (IMS-1 surface).
  2. Create a thickness pickup for this surface so that whenever the thickness of the IMS-2 surface is changed, the IMS-1 thickness changes to compensate and the Image Surface stays in the same location (use the "Minus Thickness" pickup).
  3. Move the IMS-1 to the desired location of the Exit Pupil by changing the IMS-2 thickness.
  4. Make the IMS-1 surface the Aperture Stop surface (this makes the IMS-1 surface both the Exit Pupil AND the Aperture Stop).
  5. Adjust the system aperture so that the marginal ray is at the desired height on the IMS-1 surface.
  6. Using the paraxial_trace command, note the position where the height of the chief ray (PYC) is zero or crosses the optical axis. This will be the position of the new Aperture Stop. You will have to figure out how to position a real Aperture Stop surface in this new location.
  7. Re-Assign the Aperture Stop surface to this new location.
  8. The PXS command reports the location and size of the Exit Pupil. Use this command to change the system aperture so that the size of the Exit Pupil is the desired value