An integrating sphere is used to homogenize the wavelength and radiance of light from a specific source. For this purpose, a sphere is used whose inner surface reflects as efficiently and diffusely as possible, so that maximum homogenization is achieved by multiple internal reflection.
Avantes provides the AvaSphere-xx-REFL in three different sizes (30, 50 and 80 mm) for reflection measurements. A fiber-coupled light source is coupled via a collimating lens on the upper side of the sphere, so that the surface to be measured is irradiated through a port on the underside. The reflection is then captured by the sphere independently of direction and color and transmitted as homogeneous radiation via an SMA output and a second optical fiber to a spectrometer.
The AvaSphere -50-LS-HAL-12V is a variant with an already integrated 5 W halogen light source for a significantly higher irradiance for the measurement of absolute reflection of a surface as well as for color measurements and fluorescence spectroscopy. The light source can be switched on and off via a TTL signal.
For the measurement of irradiance, the AvaSphere-xx-IRRAD series is available in the same sizes (30, 50 and 80 mm). These integrating spheres are only equipped with an input port on the underside to capture the light incident there. This allows not only the irradiance to be measured at a certain distance, but also the radiant flux of small light sources such as LEDs or lasers that fit into the input port.
The inner surfaces of Avantes spheres are made of PTFE to provide a very high and diffuse reflection property from 250 nm to 2500 nm.