Ask an Engineer: STAR module for STOP analysis

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Join us for our monthly “Ask an Engineer” event! Submit your questions between now and March 17th. The event will be hosted on ​​​​​this thread in text form with a focus on the spotlighted topic:


Topic: STAR: Bring structural and thermal analysis results into OpticStudio

Predicting the optical effects resulting from mechanical stresses or thermal variations is an important step in creating a valid digital prototype. Ask your questions about modeling surface deformations due to mechanical stress, expansion or compression of components due to temperature changes, temperature gradients or changes across a system, and effects of temperature on index of refraction.


Dates: March 4th - March 17th

Live Discussion Time: 8am - 9am PST, March 17th

Engineer:@Hui Chen - Senior Application Engineer at Ansys Zemax

Submit your questions as a reply to this thread between now and the end of the event. Items may be added in any supported language (English, Japanese, Chinese). Questions added to the discussion will be answered starting 8am Pacific on March 17th. Once the event is concluded, the thread will be closed. 

If your question pertains to a particular file, the question may be moved to a private support case. In that situation, your license support status will be considered. 


This topic is closed to new comments

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Dear all,

on one site the import of FEA data into the STAR Module via textfiles is quite “universal”, but it also requires a preprocessor (Ansys, FEMAP, Hypermesh) which automates the export of deformations considering which FE-nodes are placed on which optical surface. For Ansys Mechanical a dedicated script was already made available (see “FEA data export from Ansys”. However, users of FEMAP and Hypermesh are still excluded from the simplified workflow and space-industry is (still) dominated by Nastran users. They will feel somewhat irritated that their beloved *.op2 or *.pch format is not directly supported. Unless FEMAP, Hyperworks and hundreds of other Nastran-Preprocessors provide a similar script for the export of data, all Nastran users will need an additional/intermediate MATLAB tool to import Nastran results, then assign the surface nodes and export into STAR-Module format.

Are there any plans in future releases to import native results file from Nastran (*.op2, *.pch) or Ansys (*.rst) or Abaqus, etc.  and assign the FEA surface node numbers to the optical surface within the STAR-Module?

If the answer is “yes, planned in one of the next releases” do you have any idea when this will happen?

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Hi everyone! I'm online for the next hour answering your questions on the STAR module for OpticStudio, or anything related to structural thermal analysis capability in OS. If you have any questions related to this topic, send them in as a reply to this thread.

Thank you @ERT  for posting your question. I’ll address it shortly. I’ll also post some general FAQs about STAR.

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Hi @ERT 

Thank you for posting your inquiry on this thread! Yes, your understanding is correct. The motivation behind STAR accepting text format as input is to make sure the module is not limited to one specific FEA software, but rather it can take the structural and thermal data saved in a general text format coming from any FEA software. Our developers have published an extension that helps automate the data export from Ansys Mechanical. I’m not sure such scripts are being considered for other FEA software you have mentioned here. I agree there are two possible ways for us to move forward and help users ease their time and effort spent on FEA data export. One is to create a collection of customized extensions for common FEA software in the market; the other is to have STAR directly accept native data format used by the FEA software. I will provide your valuable feedback to our Product and Development team and have them evaluate the possibility of implementing such capabilities in STAR. New features and new capabilities are constantly being investigated for STAR since our goal is to make STAR as powerful and useful as possible. 

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Some general FAQs about STAR:

  1. What is STAR: 

STAR is a new module released with OS21.2. STAR stands for Structural Thermal Analysis & Results. It’s a tool developed by Zemax to help streamline the process of bringing in STOP (Structural Thermal Optical Performance) analysis results into OpticStudio. STAR enables OpticStudio to evaluate performance degradation due to mechanical stress and thermal effect. STAR requires a separate license to run and currently is only compatible with OpticStudio Professional and Premium Subscription licenses.

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2. FAQ on STAR data format

STAR currently only exists in OpticStudio Sequential mode. It can take in structural deformation data and thermal temperature gradient data defined in a text file format.

For structural deformation, STAR converts the deformed surface internally to a surface type similar to Grid Sag. The main difference is that the native Grid Sag requires uniform mesh while STAR supports any non-uniform mesh as defined originally in the FEA software. This significantly improves the fitting quality and enables STAR to accurately capture the structural deformation of each surface.

For thermal gradient, STAR takes in the temperature cloud and converts it internally to a surface type similar to Grid Gradient so the index variation due to temperature can be captured.

STAR streamlines the process and makes it much easier to bring the FEA results into OpticStudio. 

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3. An example of STAR operation.

Nominal system: optimized to a perfectly collimated beam as output

STAR brings in structural deformation - observe lens surface deformed and deviate from perfect spherical shape due to stress caused by mounts. STAR also brings in thermal gradient index change due to temperature variation within the lens volume.

These combined effects cause wavefront error, and the output beam is no longer perfectly collimated.

 If you are interested in this sample analysis, you can read more in our Knowledgebase at OpticStudio STAR Module - Data import and analysis tutorial.

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4. STAR future development

STAR module is constantly under development for new features and new capabilities. When STAR was first released, it can only handle single wavelength operation. Since OS22.1 we have added multiple wavelength capability so dispersion effect can be properly accounted for. This is particularly important for designing systems operating in a range of wavelengths, for example camera systems working in the visible range. STAR in OS22.1 has also added two important GUI tools, Index vs Temp plot and Inspect FEA data tool. The Index vs Temperature plot allows you to view the glass index change as temperature varies. The Inspect FEA tool provides a closer look of the FEA data set within the OS GUI by reporting the Max, Min and Median of the data points in your FEA data set.  

Currently STAR supports modeling of structural deformation and thermal gradient index effect. However, many customers have also expressed interests in modeling stress induced birefringence effect, or for STAR to support Non-Sequential mode operation. These are all great ideas. If you would like to see certain features added to STAR or certain GUI tools developed for STAR to make it easier for user to visualize and analyze FEA data, please feel free to share it with us. It will help us brainstorm and make STAR a better and more powerful tool.

A side note to complete today’s session, in February OpticStudio STAR module has won the highly esteemed SPIE Prism Award in Software. The STAR team at Zemax is very proud and honored to receive this award and will continue to work hard and make STAR a better tool in the future!

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Hi All, 

Thanks for participating in this Ask An Engineer event! Also special thanks to @ERT for submitting your question on this thread! I’ll be signing off soon but you can continue to post on this thread if you have any questions or would like to know more about our STAR module.  

We will make this Ask An Engineer a monthly event. If you have any topics that you are interested in learning, please share your thoughts with us under the Ask An Engineer announcement post. 

Have a wonderful day and see you all next time!

Dear Hui Chen,

thank you for answering my question. If there’s any feedback of your Product and Development team pleas let me know.

Have a nice day!

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Just to add one thing here to address to @ERT ‘s comments on Nastran users, our senior product manager Esteban informed me today that we in fact do have a Nastran script for Femap with Nastran FEA data export that we can share with our customers. If you are interested in the script, please do feel free to reach out to and we will be happy to provide the script!

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This thread is now closed. Thank you to @Hui Chen for an informative event :). 

If you are interested in learning more about STAR, join our user group here: STAR Module User Group | Zemax Community, By joining the user group, you will be notified when a new FAQ post or product update is published.