This article describes how to create sources of any geometrical size and shape using the Source Object. The Source Object provides the flexibility to convert any object into a source, including any imported CAD object. 

Authored By Michael Pate, updated by Alissa Wersal

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Introduction

OpticStudio has many standard light source objects available in Non-Sequential mode - a full list of them may be found in the Help Files under The Setup Tab...Editors Group...Non-Sequential Component Editor...Non-Sequential Sources...Summary of Sources. However, there may be a situation in which you want to model a source that is not immediately available in the program. To do so, OpticStudio allows users to take any geometrical object and to use it like a source. This is ideal for self-luminous objects, like filaments, or for modeling the thermal emissions from objects.

In this article we will discuss practical, real-world examples of this capability.

The Source Filament Object

The Source Filament object gives a nice starting point to quite easily make an approximate tungsten filament light source model. You are required to input the length of the coil, radius of the coil, and the number of turns in the length of the coil, along with the other standard properties of position and orientation and the number of rays to launch.

                          FRONT VIEW                                                                SIDE VIEW

                 ROTATED VIEW with RAYS                                          SIDE VIEW with RAYS

Using this Source Filament object is very quick and easy to set it up and launch your rays, but notice that they all emanate from a line source. This is probably OK for your initial system setup and design layout, but you may need to model the extended area of a typical tungsten filament source to fully characterize your illumination system.

To build a more detailed source is quick and easy using the Source Object.

Creating a Source Object

OpticStudio has the capability to bring in 3D objects from a CAD program like Creo and turn the 3D solid in to an emitting source.  Let's take a look at an example.

Procedure:

1. In your CAD program, create a tungsten filament from the proper sized wire, with the correct length, diameter, number of turns, shape of the coil, etc. and save this 3D model in STEP, IGES, SAT or STL file format.
2. Place the saved file into the Zemax...Objects...CAD Files directory
3. Start OpticStudio and go into Non-Sequential Mode from the Setup...Non-Sequential Mode path.
4. Choose the object type of CAD Part: STEP/IGES/SAT, then select the filament coil STEP file.
5. Add a new object below the CAD Part object and choose the Object Type: Source Object – This is the tool in OpticStudio to create sources out of any object you can think of creating.

The source object must be listed in the editor after the parent object. It does not need to come immediately after it: but it is usually tidier to keep the object and the source that depends on it together in one place.

You will need to tell the Source Object the row number of its parent object, and this is done through the parameter columns of the Non-Sequential Component Editor. Full details are described in the Help Files. Give the source 200 layout rays and position the source wherever you like in the optical system.

To avoid geometry errors, and to prevent rays leaving the source from immediately striking the parent object, you will want to tell OpticStudio to ignore the parent CAD object:

This means that rays will never interact with the parent object. However, that may be overly restrictive: after all, the parent object may have scattering properties, or be reflective, or have any optical property you wish. It’s usually better to use the "Rays Ignore Object: On Launch" setting or the "Ignore objects" list and to place the parent object's object number in this list. That way, when a ray is generated it fires straight out, and if it is re-imaged onto the parent it interacts with the parent object normally.

Now put a Detector Rectangle object into your design and position it properly down the z axis or where ever you choose, and give it some size in x and y. Then take a look at your tungsten filament source by doing an Analyze...NSC Shaded Model. Trace rays!

Here is another example of a Socket Head Cap Screw from SolidWorks that I saved as a step file and used the above procedure to bring into NSC OpticStudio. I made the object radiate rays at 10.6 micron wavelength and then created a bi convex germanium lens to image this “source” onto a detector.

Both these CAD files can be downloaded from the sample file link of this article.

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