Skip to main content
Solved

merit function for tilted edge interference?

  • August 13, 2024
  • 5 replies
  • 125 views

John.Hygelund
Fully Spectral
Forum|alt.badge.img+1

I seem to be tripped up a simple problem. I want to identify the edge interference (negative edge air thickness) shown in the red circle. 

What merit function will work?

Thanks for any help or guidance,

John

Best answer by Jeff.Wilde

@John.Hygelund:

One option is to just employ simple geometry.  It takes a few MF operands to do the calculation, which makes it slightly tedious but otherwise straightforward. For a rotation by theta, the trailing air gap at the edge of the lens changes by dZ = R tan(theta), where R is the mechanical semi-diameter and theta is assumed to be a reasonably small angle.

Here is an example before rotation,

and then after a 5-degree rotation,

Regards,

Jeff

View original
Did this topic help you find an answer to your question?

5 replies

Mike.Jones
En-Lightened
Forum|alt.badge.img+3
  • En-Lightened
  • 113 replies
  • August 13, 2024

ETGT is a good start.  Make it large enough to prevent negative ET all along the tilted lens.

Another way is to use NORD, the normal distance to the next surface.  Use several (X,Y) values along where edge interference can occur, and that will keep it from intersecting the next surface.


John.Hygelund
Fully Spectral
Forum|alt.badge.img+1
  • Author
  • Fully Spectral
  • 71 replies
  • August 13, 2024

@Mike.Jones , 

Thanks for the reply. I have tried both of your suggestions without success. The operands show the nominal air gap, but don’t seem to update when the first lens is tilted. I must be missing something. Any further suggestions will be greatly appreciated.

 


John.Hygelund
Fully Spectral
Forum|alt.badge.img+1
  • Author
  • Fully Spectral
  • 71 replies
  • August 13, 2024

Update:

If I remove the surface curvature, the NORD operand look to work as expected, but not the ETVA/ETGT operands…

Maybe this is a clue to finding a solution?

 


Jeff.Wilde
Luminary
Forum|alt.badge.img+3
  • Luminary
  • 490 replies
  • Answer
  • August 14, 2024

@John.Hygelund:

One option is to just employ simple geometry.  It takes a few MF operands to do the calculation, which makes it slightly tedious but otherwise straightforward. For a rotation by theta, the trailing air gap at the edge of the lens changes by dZ = R tan(theta), where R is the mechanical semi-diameter and theta is assumed to be a reasonably small angle.

Here is an example before rotation,

and then after a 5-degree rotation,

Regards,

Jeff


John.Hygelund
Fully Spectral
Forum|alt.badge.img+1
  • Author
  • Fully Spectral
  • 71 replies
  • August 14, 2024

Thank you @Jeff.Wilde,

Your example is much appreciated. My naive assumption was there would be a built in merit function that would account for edge thickness with coordinate break rotations… But I can certainly use your approach from my task. Thanks again.


Reply


Cookie policy

We use cookies to enhance and personalize your experience. If you accept you agree to our full cookie policy. Learn more about our cookies.

 
Cookie settings