This article describes how to generate any desired ray set from an RSMX Radiant Source Model file.

Authored By Dr. Sanjay Gangadhara

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Introduction

The most general description of a complex source is given in a Radiant Source Model (RSMX) file. This file contains the measured radiant or luminous intensity of the source as a function of wavelength, position, and angle. As such, this file can be accurately used to characterize the behavior of the source in both the near- and far-fields.

This article will show how to generate a ray set from a downloaded RSMX file in order to model a complex source.

Generating a ray set in OpticStudio

To model a source described by an RSMX file in a ray-tracing program such as OpticStudio, the data contained within the RSMX file must be used to generate a ray set. This may be done within OpticStudio itself, using the following steps:

1. Download the RSMX file using the “Download Radiant Source Model Data” feature.
2. Generate a spectral color format (SDF) file from this source using the “Generate Radiant Source Model^TM Rays” feature.

Both of these features may be found under “Libraries...Radiant Source Models”.

Downloading a source model

If you already have an RSMX file from a vendor (or from an in-house measurement), this step is not needed. However, if you are in the process of deciding between various sources for your optical design, it may be valuable for you to convert a number of RSMX source models into ray sets for further analysis inside of OpticStudio.

OpticStudio provides links to over 700 RSMX source models as a part of our installation. The required source models may be downloaded using the “Download Radiant Source Model Data” feature under the Libraries...Radiant Source Models...Download Radiant Source Model Data menu:

Within this feature, you may select the vendor (manufacturer) whose sources you wish to view, and additionally sort the data by lamp type (i.e. arc lamp, LED, etc.). You can ensure that all the models supplied by a particular vendor are up-to-date by selecting the option to “Download Source Catalog”.

For this example, we will download a particular model supplied by Philips Lumileds:

Once the model is chosen, hit the “Download Source Model” button to download the model (RSMX) file. The download process can take several seconds to several minutes depending upon your internet connection and the size of the RSMX file. Once downloaded, the file will be placed in the {Zemax}\Objects\Sources\Radiant Source Model Files folder (for details, see the section entitled “Folders” in the OpticStudio help file: The Setup Tab...System Group (the Setup Tab)...Project Preferences (system group)...Folders).

Generating a Spectral Color Format file

Once the source model has been downloaded, an SDF file may be generated from this model. This may be done directly within the download tool (by hitting the “Generate Rays” button) or by closing the download tool and selecting “Generate Radiant Source Model Rays” from Libraries...Radiant Source Models:

Note that any RSMX file may be chosen for the tool, as long as the file is in the {Zemax}\Objects\Sources\Radiant Source Model Files folder.

The source model that was chosen in the previous step did not include measurements of the source spectrum, so within the ray generation tool we have an option to specify the spectral distribution for the rays. Consistent with the nomenclature used by Philips in the source model description, we will choose the spectrum file for a standard cool white fluorescent (this file is provided with the OpticStudio installation). We have chosen to generate 10 million rays from this source model. The other options for this tool are described in the Help Files under the Libraries Tab. To generate the ray set once all options have been specified, simply hit “Generate Rays”.

Validating the results

To confirm accuracy of the ray generation, we may view the far-field distributions for both the RSMX and SDF files in either the Directivity Plot or the Polar Plot (both features may be found under the Analysis…Source Viewers menu). For example, a comparison between the full directivity plots for both source files at scan angles of 0, 45, and 90 degrees shows:

RSMX

SDF

The agreement is excellent, as expected.

We can also see what this source would look like when imaged onto a distant plane using the Illumination Map (found under the Analysis...Source Illumination Map; more information is provided in the article entitled “How to characterize far-field color mixing with the Source Illumination Map”). Just as with the Directivity (and Polar) Plot, the Illumination Map can be used with either RSMX or SDF files (all these analyses also work with far-field source files given in either the IESNA or EULUMDAT formats). When the RSMX file representation, we’ll also need to specify the spectrum (SPCD) file which represents the source spectral distribution:

Again, the spectrum file for the standard cool white fluorescent illuminant is included as a part of the OpticStudio installation.

Using the “Source Position and Orientation” and “Screen Size and Sampling” settings shown above, the results for the RSMX and SDF files are:

RSMX

SDF

Again, excellent agreement is observed between the two cases.

The generated ray set may now be used in OpticStudio by selecting the Source File object in Non-Sequential mode and specifying the desired SDF file as input. More details on the Source File object may be found in the following OpticStudio help file: “The Setup Tab...Editors Group (Setup Tab)...Non-sequential Component Editor...Non-sequential Sources...Source File”

Automating the process

If you would like to convert a number of RSMX source models into SDF files, and/or generate many SDF files from the same RSMX but with different ray generator settings, the easiest way to proceed is via a ZPL macro. The appropriate keyword to use is RAYGENERATOR, and a full description of this keyword may be found in the following OpticStudio help file “The Programming Tab...About the ZPL”.

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