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Hello there, I am still a new learner to Zemax.

I have an optical system of 7 lenses focusing collected light from a telescope onto an image plane. I need to collimate the incoming light and am having trouble with the merit function. I am using the RANG operand to optimize ray angle with the z axis to be zero. 

I am confused to find when I optimize the system and the merit function goes down, the field lines do not appear to cross the focal plane parallel, but rather at worse angles to the z axis. I am not worried about the weirdly shaped lenses - I know how to optimize these away. What am I doing wrong? Thanks for any guidance. 

 

Before optimizing:

 

After optimizing:

 

Current merit function: 

(Surface 11 is the focal plane in orange.)

Use the default merit function wizard and select Angular for image quality and it will automatically populate the merit function to collimate all of the fields. RANG is with respect to the local z-axis of the surface specified and each field ray-bundle will have its own general incident angle that will derive from the prescribed field angle and system focal length. In other words, you can’t have all of the fields both parallel to each other and collimated. This would be a violation of the optical invariant.

An example of using the Angular option for collimation can be found here.


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