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How to Fix Working Distance in Optimization for Objective Design?

  • February 19, 2025
  • 2 replies
  • 57 views
Rasoul

Hello everyone,

I am new to optical design and currently working on designing a simple objective using two achromatic lenses. The objective should have:

  • Effective focal length (EFL): 40 mm
  • Working distance (WD): 200 mm
  • Magnification: 5X (using a 200 mm tube lens)

I am trying to ensure that the working distance remains fixed during optimization. My question is:

  • How can I constrain the working distance in the optimization process?
  • Is there a specific operand in Zemax (or another software) that I should use to maintain the WD?

My ultimate goal is to design a confocal microscope with this working distance requirement.

I would appreciate any guidance or suggestions!

Thanks in advance,
Rasoul

Best answer by David.Nguyen

​@Rasoul 

 

The Working Distance (WD) is the distance between the specimen and the closest optical surface of your objective lens. Quite often, the WD corresponds to a Thickness in your Lens Data Editor (LDE). Depending on the orientation of your design (object on the left or on the right hand side), the WD can be the first or the last surface thickness.

If you want the WD to be a fixed 200mm, then just set the corresponding surface thickness to 200mm and that’s it (just don’t make it a variable).

If you want the WD to have some tolerance around the 200mm, you can have the corresponding thickness variable and use Merit function operands such as CTGT (center thickness greater than) and CTLT (center thickness lesser than) with values 195 and 205, for example.

Let me know if this is clear.

Take care,


David

 

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    David.Nguyen
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    • David.Nguyen
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    • February 19, 2025

    ​@Rasoul 

     

    The Working Distance (WD) is the distance between the specimen and the closest optical surface of your objective lens. Quite often, the WD corresponds to a Thickness in your Lens Data Editor (LDE). Depending on the orientation of your design (object on the left or on the right hand side), the WD can be the first or the last surface thickness.

    If you want the WD to be a fixed 200mm, then just set the corresponding surface thickness to 200mm and that’s it (just don’t make it a variable).

    If you want the WD to have some tolerance around the 200mm, you can have the corresponding thickness variable and use Merit function operands such as CTGT (center thickness greater than) and CTLT (center thickness lesser than) with values 195 and 205, for example.

    Let me know if this is clear.

    Take care,


    David

     

    Rasoul
    • Rasoul
    • Author
    • Monochrome
    • 1 reply
    • February 19, 2025

    Thanks David! 

    It solved my problem.

     

    David.Nguyen
    1 person likes this
    • David.Nguyen
      David.Nguyen

    Reply


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