Labsphere Inc.'s integrating-sphere source system offers uniform irradiance from the red to the IR and flux from ~0.6 to 5 µm. The USS-400-IG has a 1.25-in.-diameter exit port, a 4-in.-diameter InfraGold integrating sphere and two external illuminators. Its tungsten illuminator contributes flux for the visible and near-IR regions and its glowbar, for the IR. Micrometer-driven variable attenuators control irradiance levels and balance the short- and long-wavelength regions of the source spectrum. Applications include imaging systems and focal plane arrays.