The most general and accurate description of a complex light source is provided by a Radiant Source Model (RSMX) file. An RSMX file contains measured radiant or luminous intensity data as a function of:
- Wavelength
- Spatial position
- Emission angle
Because it preserves both spatial and angular characteristics, an RSMX file can accurately characterize source behavior in both near-field and far-field regions, making it ideal for high-fidelity optical simulations.
As an example, we use a tungsten halogen lamp (model 183053) from BLV Licht.
Source information and radiant source data are available at http://www.blv-licht.com/products/tungsten-halogen-lamps.html
The RSMX file can be obtained directly from the manufacturer using the “Download Radiant Source Model Data” feature.
Generating a Spectral Color Format (SDF) File
In this example, the selected RSMX file does not include measured spectral data. To address this, the ray generation tool allows the user to define a spectral distribution for the emitted rays.
For this lamp:
- Spectrum type: Blackbody
- Color temperature: 2900 K
This approach is physically appropriate for tungsten halogen sources and allows correct spectral weighting during ray generation.
Validating Ray Generation Results
To confirm the accuracy of the ray generation process, the far-field intensity distributions of the original RSMX source and the generated Spectral Distribution File (SDF) are compared.
The far-field patterns show excellent agreement, confirming that the angular intensity characteristics are preserved during conversion.
Spectral and Color Validation
Color validation is performed by comparing the spectral and chromatic behavior of the generated rays against the expected blackbody emission at 2900 K. The results show excellent agreement, as anticipated for a thermally dominated light source.
Source Illumination Map Verification
Finally, the source illumination map is examined to verify spatial and angular consistency. Once again, the agreement between the original RSMX data and the generated ray source is excellent, confirming:
- Correct spatial distribution
- Accurate angular emission
- Proper spectral weighting
Conclusion
Radiant Source Model (RSMX) files provide one of the most accurate ways to represent real-world light sources in optical simulations. Even when spectral data is not included, defining an appropriate physical spectrum—such as a blackbody distribution—allows reliable ray generation and validation.
By validating far-field patterns, color behavior, and illumination maps, designers can confidently use RSMX-based sources for precision optical system analysis.