The basic principle of operation is that light enters the integrating sphere through the sample port, goes through multiple reflections and is scattered uniformly around the interior of the sphere

Integrating sphere is a general function as a light collector. The collected light can be used as a diffuse illumination source or a measurement source. The measurement principle is based on direct illumination and indirect reflection. The basic principle of operation is that light enters the integrating sphere through the sample port, goes through multiple reflections and is scattered uniformly around the interior of the sphere. In the Avantes line of integrated spheres ,the spheres are mostly used as measurement source. The detection fiber optics are SMA-coupled to the port at the side of the sphere which is viewing illumination on a baffle, independent of the angular properties of the light at the sample port.

The reflection version is used to measure total integrated reflectance of a surface, as well as for color measurement and fluorescence spectroscopy. The inside of the integrating sphere is made out of highly reflective diffuse material; that gives a light diffuse reflection (>96 %) over a wide wavelength range (250-2500 nm).  A special gloss-trap is available for the AvaSphere-50-REFL reflection sphere to exclude specular reflection in the measurement. A light source may be connected to the 8 degree SMA-connector port through a fiber optic bundle to make the integrating sphere an ideal uniform light source. This option needs to be ordered together with the sphere. In case specular reflection needs to be included, a white reflective part can be mounted in the position of the gloss trap. 

The irradiance version of the integrating sphere can be used to measure light sources (Laser, LED, and Halogen Lamps). For the irradiance measurements of LED's a special adapter was developed to be connected to the AvaSphere-50-IRRAD. The reflection sphere has an additional SMA- connector port at 8 degrees, for direct illumination, coupling the light into sphere through a fiber and a COL-UV/VIS collimating lens, connected to a light source. The adapter can hold 3, 5 and 8 mm LED's in the correct and reproducible position inside the sphere. The AvaSphere integrating sphere family can be delivered with an active diameter of 30, 50 or 80 mm and an SMA port at 90 degrees for irradiance and reflection measurements. The AvaSphere-30 has a sample port diameter of 6 mm, the AvaSphere-50 10 mm sample port and  15 mm for the 80 mm diameter sphere. All sample ports are knife-edge, this ensures 180 degree field of view of the sample port.