Reflectometer for measuring the bidirectional reflectance of rough surfaces.

A fully automatic, four-axis gonioreflectometer is described. It has an angular accuracy of 0.3 degrees and a range of 90 degrees in both the theta(i) and the theta(r) zenith angles. The gonioreflectometer is simpler than previous designs because of its use of rotating arms rather than moving carriages to mount the optical components. Where possible, commercial components have been used to reduce the cost. A novel off-axis angular encoding scheme is also described.