IES TM-25-20

Many commercially available ray-tracing optical design and simulation software programs have been developed to support a wide variety of optical design tasks. All of these software packages can use ray files as source models. Ray files are typically generated by light source manufacturers using either an optical simulation or physical measurements using near field goniometers. These ray files are then put in a specific format for each optical design program, which allows optical engineers to integrate the light source characteristics into their optical system design simulations. Ray files describe light sources by a large number of rays with individual start location, direction, flux, and optional spectral and/or polarization data. Ray files are mainly intended for optical engineers, who are designing optical systems using light sources. Ray files are a characterization of the near field characteristics of a light source. This document provides recommendations for a standard ray file format to describe the emission properties of light sources. The ray file format contains information necessary to interface between ray tracing or other optical design, simulation, analysis and metrology software used in lighting applications.