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working f/# and image space f/#

  • November 12, 2021
  • 1 reply
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in my design, there is a big difference between image space f/# and working f/#, which one is more accurate? for example: image space f/# = 2, while WFNO = 3.05

Best answer by David

The image space f/# is the f/# of the system for a paraxial infinite conjugate -- that is for an object at infinity and the image plane at the focal length. For a system imaging finite conjugates the f/# differs. For an object at a finite distance the image side cone angle of the marginal rays decreases and the effective f/# increases. This is the working f/# for the system as-used. It is a better measure of the system as-used. You can find a good discussion of this is you follow the link in the help system for WFNO, which can be accessed conveniently by clicking the ? in the merit function editor tool bar. The help system is your friend!

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David
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  • November 12, 2021

The image space f/# is the f/# of the system for a paraxial infinite conjugate -- that is for an object at infinity and the image plane at the focal length. For a system imaging finite conjugates the f/# differs. For an object at a finite distance the image side cone angle of the marginal rays decreases and the effective f/# increases. This is the working f/# for the system as-used. It is a better measure of the system as-used. You can find a good discussion of this is you follow the link in the help system for WFNO, which can be accessed conveniently by clicking the ? in the merit function editor tool bar. The help system is your friend!


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