Hello! I’m the new Optics Engineer here at PADT, and I am excited to share the world of optic and Ansys Zemax OpticStudio with our new and existing simulation customers. I have a background in Aerospace and Defense, where I primarily worked on beam propagation optics. I have been lucky to not only design optical systems but also assemble, align, and integrate them into larger systems. I am currently pursuing a master’s degree in optical sciences at The University of Arizona, focusing on optomechanics.
About Ansys Zemax OpticStudio
Zemax OpticStudio is the world leading optical design software recently acquired by Ansys. It’s a staple in the optics world and difficult to compete with. So, it is only fitting that PADT introduces an optical engineer to their team of application engineers. The addition of Zemax to the Ansys portfolio opens up a world of opportunity within optical design. An entire optical design workflow can now be done internally with the right Ansys package.
This means that both optical and optomechanical designs can be created and analyzed and then imported into Ansys Mechanical for FEA analysis so that the effects of structural and thermal deformation on the optical performance can be analyzed and understood. And that is only the beginning of the capabilities that are possible because of the Zemax acquisition into Ansys.
I thought it would be a great idea to begin a series of blog posts centered on optical capabilities in Ansys. The blog series will include tutorials, tips and tricks, and common issues encountered by users. My first couple of blog posts will follow a Double Gauss objective as it continues down the path in Zemax OpticStudio of further analyses after initial design and optimization. If you have any topics you’d like covered, feel free to reach out to us at PADT!
How to Import Your CAD Geometry Using Non-Sequential Mode
This first blog post focuses on importing CAD geometry into Zemax OpticStudio using non-sequential mode (it is important to note that this can also be done in sequential mode using a different set of steps… but that isn’t the focus of this post). We can review the differences between sequential and non-sequential mode in a later post.
I began by using the Double Gauss sample file provided in the Samples folder of the Zemax files that are downloaded when each user installs Zemax OpticStudio. Because I used off-the-shelf optical mounts, I updated and optimized the Double Gauss example to take into consideration the restrictions on the system from the geometry of the mounts. These first steps were done in sequential mode.
Once the design was created, it was exported from Zemax OpticStudio and imported into SpaceClaim. This can be done by going to the “File Tab” and finding the “CAD Files” option in the File Tab ribbon. The “Export CAD File” window should open and look like this:
There are different ray patterns to choose from, but for this example I chose the Solid Beam option. I exported the design as a STEP file, but users should choose the file type better suited for their CAD platform.
I then imported the STEP file into SpaceClaim, where the rays are represented by the three solid beams corresponding to the three fields of the system. Exporting the rays is optional, I export the rays to ensure that there is no clipping due to the mechanical components. For those using SpaceClaim, I suggest right-clicking on the optics within the structure tree and clicking “Toggle to Heavyweight” so that the optics are considered equal to the mechanical parts and can be moved accordingly. The beam bodies can be kept as lightweight bodies as they are just being used as a reference. In the structure tree, lightweight bodies have a feather on their solid body icon.
Here is the optical design within SpaceClaim:
I then imported the CAD geometry to create my optomechanical assembly. I used a simple tube system and retaining rings to secure the optics. Here is a cross-section of the assembly:
The next step is to export the assembly from SpaceClaim into a STEP file. It is important to do this while suppressing the optical components, the optics are already in Zemax OpticStudio. When accounting for just the mechanical mounts, the assembly will look like this:
The file should be saved in the “…\Zemax\Objects\CAD Files” folder to be used as a CAD object in Zemax OpticStudio.
Before the assembly can be imported into Zemax OpticStudio, the design needs to be converted from sequential mode to non-sequential mode. This conversion can be done by clicking on the “Convert to NSC Group” icon under the file tab of Zemax OpticStudio. The corresponding window will look like this:
First step is to perform a Design Lockdown which converts idealized inputs into real manufacturing inputs, for example, it converts the system aperture into a physical aperture size. It is also recommended to run a Critical Rayset Generator, but because this example has an “Entrance Pupil Diameter” aperture type, this step will be skipped. With the “Convert to NSC Group” window ready with each option checked, the file is ready to be converted to non-sequential by pressing the “OK” button.
A new window of OpticStudio will open, and the design should mirror itself in non-sequential mode. Each field has been converted into its own source, and each focus point has a detector in place. I went ahead and added an image plane detector to capture all three fields/sources in one detector. Often, troubleshooting will need to take place during the conversion from sequential to non-sequential, as files do not smoothly convert properly. For this example, I will not go over the troubleshooting steps necessary during one of these conversions.
The mechanical assembly can now be imported into OpticStudio by inserting a new line in the Non-Sequential Component Editor before the source ellipses:
The object type should be “CAD Part: STEP/IGES/SAT.” Once the object type is selected, a window will ask which file from the CAD Files folder to use. The file name will appear in the comment section of the object as shown:
The assembly should then be imported into OpticStudio as a single component. The Z position of the assembly will need to be adjusted to its correct position. This position value may vary depending on how the two separate files were converted and imported into non-sequential mode. It is important to note that non-sequential mode uses a global coordinate system rather than a local coordinate system like sequential mode.
The final assembly has both the optical lenses with accurate optical properties, along with the geometry of the CAD assembly. The next step in this adventure involves accurately depicting the properties of the CAD assembly. In future blog posts, we can explore how to explode the CAD assembly into its individual components, and applying accurate coatings to the CAD assembly so that an accurate scatter analysis can be done.
You can download the files used here.
Until next time!
