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Ray Geometry in OpticsBuilder

This article takes the user through the Ray Geometry features of Zemax OpticsBuilder and additionally show cases various optomechanical examples which can be found in the Zemax sample files.

Authored By Flurin Herren 


All these examples and features are showcased with Creo Parametric 4 and are given installation default settings, all sample files can be found in the following directory:

  • ..\Documents\Zemax\Samples\OpticsBuilderCreo


Zemax OpticsBuilder helps CAD users to directly convert complete optical designs from Zemax OpticStudio into a CAD Environment, analyse the influence of the mechanical components onto the optical performance and export optical drawings to manufacturing. The Ray Geometry features are a vital part of the Simulation group of the Zemax OpticsBuilder tools and creating a bridge to the native assembly constraint tools of the CAD environment.

The Following features are:

  • Chief Ray - Sample file: Ultra Short Throw Projector
  • Ray Footprint Boundaries – Sample file: Flash Lidar

Chief Ray - Ultra Short Throw Projector

The Chief Ray tool generates chief rays based on the sources which are selected during the Chief Ray setup. These Chief Rays are then launched from the centre of the sources and traces along the z-axis of the optical system. The user can click on the segment of the Chief Rays and apply CAD tools to measure position and analyse the affects the mechanical components have on them. In order to showcase this feature we can use one of the sample files, after opening up the ultrashort_throw_projector.asm assembly, this initial set up is given:


After that it is necessary to set STOP Object in the Advanced settings, first the Maximum chief ray position delta has to be set, for this example we will use 0.0254mm this value is the maximum delta that the chief ray may be displaced from zero. Secondly, the Stop Object has to be defined, the Stop Object may be defined within the Prepare for OpticsBuilder settings within Zemax OpticStudio and if the initial ZBD settings are set as non read-only the OpticsBuilder user can change the stop selection.

  • Please note that all the Sample files have a Maximum chief ray position delta and a Stop Object set

After that the Chief Ray within the Ray Geometry can be applied.


In order to do so, the next step is to define which sources are included and which sources are not. As the basic set up of the optomechanical system has now been changed, the user needs to re-run a Simulation. After the Simulation is run, it make sense to hide the rest of the rays in order to properly work with the Chief Ray, this can easily be done by navigating to the Simulation Rays section of the OpticsBuilder Model Tree, right-clicking the specific Ray bundle and then choose Hide.


The user can go ahead and click on any given Chief Ray (in this example only one source was chosen), and the short menu of the Creo Parametric graphics area pops up. The Chief Ray can now interact with all the mating and measurements tools found in Creo.  

Ray Footprint Boundaries - Flash Lidar 

With the Ray Footprint Boundaries feature the user can select to show ray footprint boundaries by source, projected onto the lens surfaces. They may select multiple sources to display multiple footprints by source at the same. In order to showcase this feature, we can use one of the sample files, after opening up the flashlidar.asm, this initial set up is given.


After selecting the Ray Footprint Boundaries feature within the Ray Geometry Tool group, the source or the sources can be chosen. In the case of the FlashLidar, there is only one source, so this one is selected. 


The rays are re-simulated automatically and the footprint boundaries of the propagated light are saved as sketches onto each surface of the optical components. These sketches can then be used to design further mechanical components or can be used to constrain specific relations within the optomechanical assembly. 


The sketches also occur on the model tree of the individual components and the short menu of the Creo Parametric graphics area can be used to edited or use the sketches.


Limitations of the Ray Footprint

The Ray Footprint Boundaries features has some limitations, first of all there are some unsupported cases:

  • Systems with beam splitters will only show a path straight through path unless the advanced settings are changed to use polarization to split the NSC rays.
  • Systems with reflections from coatings where the intended main path is not a straight through path will not show the reflected path unless the advanced settings are changed to use polarization to split the NSC rays.
  • Systems where rays are colinear and do not create a footprint on any extent. An error/warning message will be displayed if this happens.
  • Polarization dependent systems.

For more information on these unsupported cases, please refer to the Help File within your Zemax OpticsBuilder: Unsupported Cases for Ray Footprint Boundaries.

Further, it also important to note that the Ray Footprint is a probabilistic distribution of where most of the light will fall, it should be expected that a few rays which are outliers will fall outside of ray footprint.

And lastly, as shown on the image below multiple footprints on a lens indicates that the light is not following intended path and possibly the beam is getting clipped, or image contamination is occurring. You can check how are these footprints getting generated by closely looking at naming of each footprint within the model tree of the specific component.


In the nomenclature S stands for source#, F for face index, P for path level (how many segments away from the source the ray is) and O for object# the ray hit before. So, the highlighted footprint here is made of rays that are from Source 1 which hit face 2 of the lens and have a path level 3 also these rays have hit object 5 before hitting the face 2. 


Additional Information 

If you are facing an issue with the usage of Zemax OpticsBuilder, you may contact (Active license users only). Our team of optical and mechanical experts are more than happy to help you. 

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