Edit optics with SOLIDWORKS and OpticsBuilder

This article provides a walkthrough introduction on how to edit optics from an initial system in CAD and how to analyse said optical system with OpticsBuilder after mechanical components have been added. The show-case example is a smart phone lens system from a worldwide operating manufacturer which consist of five lenses, a cover glass and an infrared filter. The main objective is to extend these lenses with complex edges, so that they can be fitted into a mechanical mounting.

Please find the example within: ....\Documents\Zemax\Samples\OpticsBuilderSW

Authored By Flurin Herren 

Introduction

This design started as a non-sequential optical system that was created and optimized in OpticStudio, after that the system was converted into a ZBD. file with the Prepare for OpticsBuilder tool. 

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The two most important points to consider when using Prepare for OpticsBuilder is that firstly a sequential optical system will be converted into a non-sequential system (not the case in this example) and secondly that in the File Loading section of the Prepare for OpticsBuilder feature, the Read-only box should be unticked if the mechanical engineer needs to have the rights to edit the core optical properties.

After that the system is imported into SOLIDWORKS 2018 via the Import .ZBD file feature. 

Edit Optics with SOLIDWORKS

As a first step the given optical system is analysed, and the further steps are planned. 

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Part List: 

  • Infrared Filter A
  • Lens (LB)
  • Lens (LC) 
  • Lens (LD) 
  • Lens (LE) 
  • Lens (LF
  • Cover Glass G

The prerequisites for the extended lens edges are that mechanical baffle rings must be retained between them. And the main mounting, which holds the optical system and is denoted in this article as the Barrel, should be edited as little as possible. Ideally the Barrel should only be extended to hold the IR Filter (A) and the Cover Glass (G). 

  • Disclaimer: For display purposes the IR Filter (A) and the Cover Glass (G) are retained with the Barrel Assembly, in a real-life application these two components would be retained by the cellphone housing which is separate from the optomechanical assembly housing the lenses. 

As a next step an OpticsBuilder Simulation is carried out and the spot size, the amount of beam clipping and the image contamination are reviewed. As there are no changes made to the system, all the metrics should meet the allowable delta specification and a green checkmark should be displayed. 

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With this step done, the optics can now be edited. 

Edit the optics 

To add the mounting edges to the lenses, the measurements of the unmodified Barrel (See image in next section, Add and adjust the mechanical components) are taken into consideration.  

To edit the first lens, it is opened in its own file (Assembly tab>right click on part>Open). After that, an additional sketch is drawn onto the side of the lens. By appending a centerline to the optical axis of the lens, the added sketch can be revolved around the lens. 

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In the next step the modified lens is updated in the assembly. This means that the fine adjustment of the complex edges can be done by modifying the sketches directly in comparison with the neighbouring lenses and onto the Barrel. As marked on the image below, there are still gaps considered for the Baffle rings. These are implemented in the next section. 

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Add and adjust the mechanical components 

Apart from the Baffle rings which are off-the-shelf components, the given Barrel and Front Baffle are modified so that the mechanical assembly can retain the newly added optical components (A and G). Additionally, to improve the optical properties of the optomechanical system, two different apertures are increased (red marked on image section C and D). 

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Optical performance analysis with OpticsBuilder 

After the optomechanical system is fully designed, the system can be tested with the OpticsBuilder validation features. As a first step, the four Baffle rings are included (Region of Interest, left in the image below) in the optical performance tests. Then the system is simulated, and the results displayed. 

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Spot Size- 

The spot size delta is calculated from the absolute value of the difference between OpticsBuilder Baseline and OpticsBuilder modified configurations. While the OB Baseline configuration only contains optics and aperture surfaces, and the modified configuration also contains mechanical geometry. As the spot size has a green checkmark, the modified configuration has the same value as the baseline configuration. 

Beam clipping 1.38%, 

Rays that that hit a detector in the OpticsBuilder baseline configuration and do not hit any detector in the OpticsBuilder modified configuration are considered clipped. So, the percentage of clipped rays is defined by taking the ratio of the flux that does not hit a detector in the OpticsBuilder modified configuration divided by the flux that does hit the detector in the OpticsBuilder baseline configuration multiplied by 100. As the Baffle rings should prevent the rays from propagating through the upper parts of the assembly, a minor amount of beam clipping is tolerated. 

After that the two modified mechanicals components are included in the Region of Interest as wellOpticsBuilder will automatically display two yellow hazard signs next to these two mechanical components. The reason for this is that there are new mechanical components which might influence the optical performance, so the optical simulation should be executed again. 

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Spot Size 1.4474  

The spot size delta, for which the description of the calculation can be found above, increased by approximately 0.4. So, it can be concluded that the averaged spot size over all sources has increased by a factor of 1.4. Given the fact that these two modified mechanical components are the main mounting of the optomechanical system, in a first draft this value can be declared as sufficient. 

Beam Clipping 5.17% 

The Beam clipping has increased by approximately 4 % which in a first draft can also be declared as sufficient. Additionally it is also given that the initial approx. 1.5% of Beam clipping which are caused by the baffle rings are actually indented. The reason here being that the functionality of the baffle rings is to prevent stray light from spreading out in the barrel.

Next Steps: As a next step the optomechanical system can be reviewed with the optical engineer and the optical performance properties analysed. If needed the optomechanical system can either be further improved with the CAD system, exported back into OpticStudio with the Export .ZBD file feature (*1) or declared as completed. 

(*1) Important to note here is that because the optics were edited with a CAD feature, they are not solely optical components anymore. So, they can be either defined as CAD Part: SolidWorks or CAD Part: STEP. As seen in the image below, the red marked objects are the five lenses which were edited. In contrast, object 11 and object 29 are the IR Filter and the Cover Glass respectively. They are still defined as a Standard Lens because they have not been edited with a CAD program.  

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If the optical engineer has reviewed the optomechanical system and has defined the optical performance properties as sufficient (which is the case here), the allowable deltas can be changed within the System settings of OpticsBuilder (Note that the allowable deltas can also be changed when the ZBD file is sent back to OpticStudio, in that case the ZBD file must then be updated within OpticsBuilder). 

 

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As a final step the allowable deltas can be printed automatically as a part of a Report. 

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For the Assembly and OpticStudio file, please refer to the Zemax sample files (Directory given before Introduction).

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