Integrating Spheres Create ’Artificial Sunshine’

Joe Jablonski and Scott Jennato

When testing a camera system or a material's weathering performance, researchers need a stable, uniform light source that closely mimics the conditions that the product will encounter in its actual application. For devices that work on Earth or that image Earth, the test light source must simulate the solar spectrum.

Several industries and applications require sources to generate uniform radiance fields that simulate the solar spectrum at or near 100 percent albedo (the ratio of reflected radiation to incident radiation). A xenon discharge lamp provides the closest match to solar spectra of any single source. However, the phenomenon of "arc wander" makes xenon sources inherently unstable.

An integrating sphere can help. Integrating spheres are insensitive to the directional input of the source and can act as a "mixing bowl" to combine the spectral output of several sources, such as xenon with tungsten-halogen. This mixture can produce a stable, uniform source with 98 percent radiance uniformity at 100 percent albedo levels. . . .

Meet the authors

Joe Jablonski is the director of product support for Labsphere Inc. in North Sutton, N.H. He has a BS degree in physics and optics from the University of Lowell.

Scott Jennato is the marketing and new-product development director of Lab-sphere's component and systems group. He has a master's degree in optics and electromagnetics from Northeastern University and an MBA from the University of New Hampshire.