A fully automatic, four-axis gonioreflectometer is described. It has a
n angular accuracy of 0.3 degrees and a range of 90 degrees in both th
e theta(i) and the theta(r) zenith angles. The gonioreflectometer is s
impler than previous designs because of its use of rotating arms rathe
r than moving carriages to mount the optical components. Where possibl
e, commercial components have been used to reduce the cost. A novel of
f-axis angular encoding scheme is also described. (C) 1998 Optical Soc
iety of America.