The large diameter integrating sphere (LDIS) measures total visible transmittance of complex light redirecting/diffusing samples with large scale non-uniformity. The instrument is a sphere 6.5 ft (2 m) in diameter with up to 34 inch measurement aperture (11-15 inch typical).

The theory and application of this sphere is described in the following two papers:

1. Kessel, Jeffrey. "Transmittance Measurements in the Integrating Sphere." Applied Optics 25 (1986): 2752-2756. [PDF]
2. Kessel, Jeffrey, and Stephen E. Selkowitz. "Integrating Sphere Measurements of Directional-Hemispherical Transmittances of Window Systems." In Illuminating Engineering Society Annual Technical Conference. St. Louis, MO, 1984. [PDF]

The integrating sphere has been used to develop measurement standards for characterization of tubular daylighting devices.

Attributes and Capabilities:

• Motorized position relative to the sun allows rapid measurement of many incidence angles
• Validates optical models for light redirecting samples under variable angle of incidence
• Basis for NFRC 203 standard development