I am wondering your sequential tolerance analysis techniques for athermalized lens system. I am trying to do tolerancing on my system firstly by removing MCE because I cannot control tolerances and thermal effects at the same time it gives an error. After that, I run sensitivity analysis. Then, I check worst offenders. By obeying rules of thumb for tolerancing, I am trying to tighten the tolerances by controlling the sensitivities ( I am not successful in this part, though) . Then, I don’t know how to make my lens athermalized again. To summarize, I am stuck in tolerancing, and I cannot develop new technique for myself. Therefore, I need your help so I can find a way to tolerance my system. :(
Additionally, I am open for your advice in worst offender’s sensitivity analysis.
Thanks in advance!
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Hi Meryem,
First, I want to point out that OpticStudio’s thermal analysis is a first-order prediction (using linear CTE for geometric changes and 3rd order polynomial for index changes). You can only model Rigid Body Motion with the built-in tools; you cannot model surface deformation or thermal deformation.
Both the Make Thermal and the Tolerancing Wizard tools are designed to work independently of each other.
If you want to combine the two tools via the GUI, you will need to run the Make Thermal first (so that the MCE has multiple configurations with a “T” thermal pickup on the operands) and then you’ll need to use the TMCO tolerance operand to control each MCE value.
The following would be an example for a singlet:
If you don’t want to do this via the GUI, then you can create a very simple ZPL/ZOS-API script which will tolerance your Make Thermal MCE data. Tolerancing is a 2 step process:
Perturb each defined operand
Optimize compensators for best performance
Report MFE
If you need to include the thermal effects of the material itself (dn/dT), then you’ll need to create your own script (either ZPL or ZOS-API) where you will:
Create a copy of the material in a new catalog
Change the T0 refractive index
I suggest changing to the Conrady formula since this only has n0 + 2 coefficients so it’s easier to control the y-axis intersection of the curve (the refractive index/TIND) and the relative slope of the curve (the Abbe number/TABB)
Copy the old Thermal Coefficients to the new material
Save the new catalog and then load the new material(s) into your system
Perform a tolerance analysis on the T0 configuration
Repeat for each MC run
This still will only give you a first-order thermal performance and you’ll need to run a full FEA (with STAR) to get the full thermal performance for your lens + environment.
If you want a shortcut, I would suggest simply running a tolerance analysis on your nominal temperature, find the worst case offender, manually open, run the Make Thermal on the worst case offender, and record the metrics. Thermal performance should be the best at the designed temperature and you will not improve your system performance at non-design temperatures.
