OpticsBuilder enables CAD users to detect errors early, reduce back-and-forth communication with Optical Engineers and avoid expensive physical prototyping by delivering analysis tools that show the impact on beam clipping, image contamination, and spot size change performance metrics. Using the OpticStudio physics core, OpticsBuilder allows CAD users see the impact on performance metrics, find errors within the native CAD environment and lower manufacturing costs. CAD users don’t have to wait for input from an Optical Engineer to know how their packaging is impacting optical performance. This helps to streamline communication between optical and mechanical designs while ensuring that the optical performance is maintained.

Authored By Jacob Hart

Introduction

OpticsBuilder enables CAD users to detect errors early, reduce back-and-forth communication with Optical Engineers, and avoid expensive physical prototyping by delivering analysis tools that show the impact on optical performance.

Perform a simulation in OpticsBuilder for Creo Parametric

Precision settings

Before simulating an optical system the system settings window should be opened by clicking on System Settings in the ribbon.

Selecting the Precision settings tab allows the number of rays to be set for a ray trace. Zemax suggests that 10,000 rays be used for a high level ray trace, with more rays being used as the design is refined. Up to 100 million rays may be traced, but at least 150 GB of disk space is needed to ray trace with 100 million rays.

The rendering mode for parts may also be changed in Precision settings. Selecting the dropbox under Trace Mechanical components as changes the rendering mode between rendering the system as multiple individual parts or as a single part for each surface property in the optical system. For large models with many faces tracing all components as a single part (per model surface property) may significantly speed up ray tracing.

Design settings (from .ZBD file)

During ZBD file creation the Optical engineer sets the defaults for whether scattering and ray splitting is enabled, allowable deltas are set for performance metrics, and any notes from the Optical engineer are displayed. These settings may be changed by the CAD user, with the ability to reset to Optical engineer defaults in the lower left corner of Design settings.

Enabling scattering enables the scatter profile for each surface. When scattering is disabled all mechanical surfaces have mirror surface finishes. 

Enabling ray splitting causes scattered, reflected, and transmitted rays to split off from a parent ray when hitting optical or opto-mechanical surfaces. This more accurately models the flow of energy in the optical model while increasing ray trace time as the number of rays traced grows.

NSC ray trace settings (Advanced settings)

The same non-sequential (NSC) ray trace settings are used in OpticsBuilder as are used in OpticStudio.

These settings affect:

• How many times a ray may split and/or intersect with surfaces before being clipped 
• Maximum number of source rays to commit to memory
• The relative and absolute ray intensity cutoff before being clipped
• The spacing between cemented lenses
• How far to draw rays after they miss all geometry before being clipped

Changing NSC ray trace settings can dramatically affect simulation times. Increasing the number of intersections or segments rays may have causes rays to be traced through more beam paths as rays scatter off surfaces or are split through ray splitting. Decreasing the minimum relative or absolute ray intensity values causes rays to be traced longer before meeting the minimum intensity criteria before being clipped. Experimenting with NSC ray trace settings is important when optimizing a file for ray trace time while maintaining an acceptable level of simulation accuracy. 

Performing a simulation

In Creo, click open and navigate to /Documents/Zemax/Samples/OpticsBuilderCreo/Heliar.

• Open heliar_37mm.asm.
• In the ribbon, click Simulate.

OpticsBuilder will automatically:

1. Add all optical components to the Region of Interest
2. Define a black anodized scatter profile to each mechanical part without a scatter profile
3. Perform a baseline ray trace to record the performance of the optical system without mechanical components
4. Perform a second ray trace to record the performance of the optical system with mechanical components
5. Compare the two datasets and calculate the difference in spot size, beam clipping, and image contamination
6. Display simulation rays in the graphics area
7. Open the results window

The results window

The results window is displayed at the end of a successful simulation. 

If a performance metric is greater than its allowable value it is highlighted in red in the results table. Any performance metric in white may be clicked to display the metric value instead of a green checkmark.

Detectors may be viewed by selecting Show Detectors in the results table. 

For each detector field and configuration the RMS spot size, number of hits by rays, peak irradiance, and throughput (total power on detector) are displayed.

Selecting Show Clipped Rays or Show Contaminating Rays in the results table will plot rays that never strike a detector or rays that strike an unintended detector, respectively. Plotting the clipped ray set is useful for determining which mechanical component(s) is blocking rays.

In this case the clipped ray set (typically purple) indicates that the annulus in the center of the Heliar assembly is clipping rays. Editing the annulus to increase its inner diameter improves image quality and reduces beam clipping. Enter part mode to edit the annulus in sketch mode, exit sketch mode, and close the part to switch back to assembly mode. In assembly mode a simulation may be run again to see the image performance metrics for the modified system.

The beam clipping ray set now shows that the pressure ring on the first lens is clipping rays. Further part modification and simulation may be performed to bring all optical performance metrics below their allowables.

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