Hi Saeedeh,

Thank you for your inquiry!

I assume when you say the working distance as the distance between last surface and image surface, your goal is to place the image surface at the smallest spot size? Or in other words, your goal is to introduce tolerance due to manufacturing error and observe the change in the image location that provides the smallest spot size?

If that's the case, what you can do is using RSCE operand in the Merit Function editor. RSCE reports the RMS spot radius referenced to centeroid. You can then set Merit function as your tolerance criterion and set the working distance as the Compensator. This way, when you tolerance the system, OpticStudio will vary the working distance so a smallest spot size can be achieved on the image surface. In the Tolerance text output or the Tolerance Data Viewer, you'll be able to see both criterion and compensator statistics being reported. 

Below I use the Cooke triplet as an example to show how to do this. I also attached this file here for your reference. In this file, I tolerance the radius of curvature of the last surface, use RSCE operand in the Merit function as criterion, and use the working distance as compensator. In the Tolerance Data Viewer, you can see the list of working distance and RMS spot size reported for the 20 Monte-Carlo runs performed. 

Let me know if you need clarifying or have any other questions. 

Best regards,

Hui

Dear Hui,

Thanks for your reply.

I want to see the Monte carlo analysis run as a criterion of Merit function. Merit function would be my working distance (distance between last surface till image) and the goal is to lowest wavefront error. Can I use STHI or optical pasth difference in merit function?

Thank you

Hello Saeedeh,

If you are interested in the smallest wavefront error instead of the smallest spot size, then you can use the RWCE operand instead of RSCE. The RWCE operand calculates the RMS wavefront error in waves, with respect to the chief ray. It uses a Gaussian quadrature method that is accurate for systems with unvignetted circular pupils.

Best,

Csilla

Hi Csilla, 

If I want to minimize the RMS spot radius..should I put just RSCE on the merit function list and Optimize? where should I found the results achieved?