FRED Stray Light Analysis

Stray Light AnalysisFRED is the proven opto-mechanical analysis package for performing accurate stray light calculations and provides engineers with a complete toolbox of stray light utilities.

Full system specification can be accomplished by using the 13+ surface and volume scatter models, 18 material definition types (including real and imaginary refractive index values) and 7 coating types.

These physical properties can be applied to any geometrical object in the model to produce realistic simulations of light interaction.

FRED's stray light capabilities begin with "real world" scatter models. FRED has the following predefined bidirectional scatter distribution functions (BSDF):

  • Lambertian
  • Harvey-Shack (smooth optical surface scatter)
  • Abg (smooth optical surface scatter)
  • Phong (cosn from specular; does not obey reciprocity but is common in computer graphics)
  • Diffuse black paint (scaleable generic diffuse black paint)
  • Particulate distributions (MIL-STD-1246, uniform, Gaussian)
  • Diffuse/Lorentzian binomial and polynomial models
  • Power Spectral Density (tabulated data)
  • K-correlation
  • Tabulated BSDF
  • User-defined scripting model

FRED’s visual interface allows instant model feedback such as scatter model parametrization verification through 2D or 3D angle and B-B0 plots and total integrated scatter (TIS) calculations.

After a raytrace FRED compiles a list of scatter and ghost paths from source to a specified detector, and these paths can be re-drawn to the 3D view for visualization. Additionally, these raytrace paths can be interrogated using any of FRED’s built in or user-customized analysis routines by simple application of ray path filters.


An effective optical design and analysis program must not only have the proper tools available, the user must be able to accurately and confidently use those tools in practice. FRED’s combination of usability and accuracy make it the industry standard for stray light analysis.