Hi everyone, the Optical Engineer is back, and it is time to revisit the thermal soak analysis of the Double Gauss objective. This time, I wanted to address some of the common questions we get at PADT involving the STAR Module within Ansys Zemax OpticStudio (AZOS) and exporting deformation data from Ansys using the “Export to STAR” ACT extension. The intention of this article is to address some details in the workflow rather than a full tutorial. Please see Knowledgebase articles on the Zemax website for detailed tutorials and examples on using the STAR module.
Last time, we ran a thermal soak on a simple Double Gauss tube assembly in Ansys Mechanical. Our results consisted of total deformation at 5 different temperature ranges, the results shown below are for the maximum temperature of 40° C.
The next steps in this workflow are to export the deformation results at each temperature and import each into AZOS with the STAR module. First, the “Export to STAR” ACT extension must be downloaded from the Knowledgebase article OpticStudio STAR Module: Ansys Data Export Extension – Knowledgebase (zemax.com). Once the extension is installed and loaded into Ansys WorkBench through the ACT Start Page, the “Export to STAR” tab in Ansys Mechanical should be available. A more detailed tutorial on these steps is provided in the linked Knowledgebase article from the Ansys Zemax team.
There are two options within the “Export to Star” tab, one to export lens data, and the other to export mirror data. As their names imply, the Export Mirror Data option will export the deformation of a mirror, which is a single surfaced optic. The Export Lens Data option will export the deformation of two surfaces that make up a lens. It will also export the thermal data of the lens volume and export it to a separate results file. In a thermal analysis, an Export Temperature to STAR object is inserted in the results which only gets the thermal data of the lens volume. For this example workflow, a static structural analysis is being performed with a thermal load.
Each lens will need its own “Export Lens to STAR” object in the solution Branch of the Static Structural analysis.
Each object was renamed to match its corresponding lens. These objects can be renamed by right-clicking and choosing the rename option, or by highlighting the object and pressing F2.
The doublets in the Double Gauss design, as shown in the optical layout, will need two Export Lens to STAR objects in the Results branch of the analysis, one per each lens. This means that the results of both lenses will share a surface whose deformation should match. This approach should capture the all information of the doublet, as opposed to treating the doublet as a single lens and ignoring the deformation on the intermediate surface. So, for our Double Gauss objective there should be 6 Export Lens to STAR result objects.
Each Export to STAR object must be defined with the details of the front and back lens surface, the Zemax ID number, the coordinate frame of each surface, and the desired Export Timesteps. For this example, all timesteps were exported, but single timesteps may also be chosen.
The Zemax ID corresponds to the row number of the surface in the Lens Data Editor in the OpticStudio file.
A key thing to consider when setting up the details to these results, but also when performing FEA on an optical system like this, is the coordinate system. I have found that the best approach is to match the coordinate frames between AZOS and Mechanical. If this approach is taken, the coordinate system for each surface can be set to Global Coordinate System. This global coordinate system matches the global coordinate reference system within AZOS.
Changing the coordinate system of the Double Gauss example was done in SpaceClaim so that it matched the coordinate frame of AZOS.
Once each lens is set up with an Export to STAR tool in Mechanical, the model can be solved and the resultant deformation of each lens will be saved at each timestep and dated.
Each folder contains the deformation and temperature data for each surface. Using the STAR module, the deformation results can be loaded using the Load FEA Data tool within the STAR tab.
Once the FEA data is loaded, a coordinate system transformation should not be needed if the coordinate system of the CAD matched the coordinate system of AZOS. From here, the FEA data is fitted by clicking OK in the Load FEA Data tool.
The next steps in the workflow are to verify the fit assessment and do an alignment check of the FEA on each lens surface. From there the optical performance can be evaluated by incorporating the FEA deformation results.
Get Started on Using the Star Module in Your Next Simulation
The STAR module is meant to create an easy and fast way to implement FEA results to analyze structural and thermal effects on optical systems. With the ‘Export to STAR’ extension, exporting the deformation results from Ansys has made the process even quicker! As always, feel free to reach out to us here at PADT with any of your questions!