Dear Zemax Support Team,

I have a question regarding the Huygens PSF calculation in afocal optical systems. Since afocal systems do not form a real image plane, I would like to understand how Zemax handles this scenario. Specifically:

• Does the Huygens PSF in an afocal system represent the far-field angular distribution (similar to an angular PSF)?
• How does Zemax define the reference plane for integration when there is no real image plane? Is it based on the paraxial image plane, a user-defined surface, or another method?

Any clarification or documentation on this would be greatly appreciated.

Thank you for your support!

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