Radiance to Irradiance Conversion Training Level Intermediate Dr

Radiance to Irradiance Conversion Training Level: Intermediate Dr. Richard Young Optronic Laboratories, Inc. 1 Optronic Laboratories

Radiance to Irradiance Conversion Geometry Source Detector Let us start off with a source of radiance, e. g. a sphere source, and a detector 2 Optronic Laboratories

Radiance to Irradiance Conversion Geometry Source Detector Each point on the detector is illuminated by light within the solid angle (cone) to the source 3 Optronic Laboratories

Radiance to Irradiance Conversion Geometry Source Detector A large distance between source and detector is required for even illumination. 4 Optronic Laboratories

Radiance to Irradiance Conversion Geometry Source Area = A Detector Distance = d The solid angle is calculated by A/d² when d²>>A 5 Optronic Laboratories

Radiance to Irradiance Conversion Geometry Although it is a simple formula, it works well at d>10 x source diameter 6 Optronic Laboratories

Radiance to Irradiance Conversion Geometry Source Detector If the source is uniform, then the light in the solid angle to the source… 7 Optronic Laboratories

Radiance to Irradiance Conversion Geometry Source Detector …is equal to the light in the same solid angle from the source. 8 Optronic Laboratories

Radiance to Irradiance Conversion Geometry Source L [W/(cm² sr)] Detector x sr E [W/(cm²)] Irradiance from Radiance: E = L * A/d² Radiance from Irradiance: L = E * d²/A 9 Optronic Laboratories