Light entering the sphere bounces many times off its white lining, typically barium sulfate or sintered PTFE, until it reaches the sample port from every direction at once. This produces the diffuse illumination that d/0 and d/8 instruments need for brightness, opacity and whiteness. Aging, yellowing or dirty linings shift readings, so sphere condition is one of the first suspects when a lab's numbers drift.
Readings started wandering after the sphere got dusty, so service is coming out to clean and recoat it.
Also heard as
- sphere
- Ulbricht sphere
Related terms
Spectrophotometer
Instrument that measures reflectance across the visible spectrum and computes brightness, whiteness, opacity and color.
d/0 geometry
Measurement setup with diffuse illumination of the sample and viewing perpendicular to its surface.
Gloss trap
Black absorbing port in an integrating sphere that removes mirror-like surface reflection from a measurement.