This article takes the user through the workflow of an optomechanical system, from the initial optical design all the way to the performance analysis of a full optomechanical system. The optical design process begins with Ansys Zemax Opticstudio (Zemax), where the optical design is created and optimized. An optomechanical CAD model is then generated using Creo Parametric 9 (Creo). The optical design is then transferred to Ansys Speos (Speos) for further analysis. The updated optomechanical model and optical design are merged in Speos to create the complete optical product design, enabling in-depth analyses such as a stray light analysis.

Authored By Akhil Dutt Vijayakumar, Flurin Herren

Introduction

Optomechanical product design can be streamlined by the ongoing improvements to Zemax and Speos. These improvements will allow users better product interoperability and greater flexibility at each step. Users can identify and address challenges that arise during each step of the design process, ultimately reducing the number of iterations needed and speeding up time-to-market.

Our show case example in this workflow is the Single Gauss 25mm. This example is a high-performance system for camera applications with the main advantages of compact size and low distortion.

You can find the Single Gauss 25mm file attached at the bottom of this article and also in the Zemax installer:

• …\Documents\Zemax\Samples\OpticsBuilderCreo\Single Gauss 25mm

Ansys Zemax OpticStudio

We start off with the optimized optical system of the Single Gauss 25mm in Optic Studio's sequential mode and analyze the spot sizes.

In the figure (1) above, three field points and three wavelengths which cover the visible range of this system are shown. The spot size diagram includes all three wavelengths at each field point.

Below are the values from the on-axis spot size, which can be found within the Text tab of the Spot Diagram feature window.

Next, a mechanical stop will need to be designed to account for the addition of the optical stop (SYS STOP)

We can find the Index of Refraction and the Abbe number if we set the Solve box of the Material parameters to Model.

From here, we can use the Export Optical Design to Speos tool found in the Zemax File tab. This tool automatically converts our optical system to an optical design file that saves all optical geometry in an .ODX format.

The mechanical mounting can be generated as STEP files using the CAD File Export tool in the Zemax File tab. The STEP files can be opened in Creo Parametric 9 and added to the top-assembly.

Tip: It is useful to make a surface, preferably a stop surface or an image plane, as the global coordinate reference before performing the export. This ensures that the CAD files and the .ODX file can be easily aligned at the end design in Speos.

CAD Environment

By performing the STEP export in Zemax, a CAD design of the optical lens assembly is created. The mechanical parts were already designed within CAD as native CAD Parts including properties such as Sketch, Revolve and Extrude.

Depending on the use case, an exported STEP part can either be added directly to the assembly or re-created as a native part.

In this workflow example, the mechanical parts are already finished and added to the optical system. The optomechanical assembly is then saved as an .ASM file that contains both the optical and mechanical geometries.

Ansys Speos

The .ODX file carries all the properties defined in the Lens Data Editor in Zemax and can now be opened in the Speos environment for further analysis. The .ODX file can be opened in Speos as: Light Simulation>Components>Optical Design Exchange> Browse> 25mm Single Gauss system (Figure 5). After the .ODX opening dialog closes, select the Execute button to finish the final step of Import process. 

The .ODX file contains the details of the lens assembly which can be seen using the Enlarge tool, found next to the Optical Design Exchange tab in the top bar. In the Assembly tab, select ‘File’ icon to import the optomechanical assembly from Creo (Figure 6).

Use the global coordinates to align the .ODX file and the .ASM files correctly. The .ODX file includes detailed optical components that can replace the existing optical components from the optomechanical assembly. The final step is to delete the optical components from the CAD assembly file and save the new design in a Speos file format .SCDOCX.

Summary

To summarize this workflow, let's look at a detailed overview in which the conversions between tools and entities have been marked with a letter:

1.  Transfer the optical system from Zemax to Speos by generating an .ODX file. The .ODX file is then opened in the Speos environment.
2.  Transfer the optical system from Zemax to a CAD environment using a STEP file.
3.  In CAD, add the optical design to the mechanical assembly, and then transfer the optomechanical assembly to Speos.