An apparatus for measuring a goniometric reflection property of a sample
has: one or more illuminators; a toroidal mirror which is rotationally
symmetrical around a center axis effectively contacting with a surface of
the sample; a light receiver having an incident aperture on the center
axis; a rotating optics which rotates around a rotation axis which
effectively coincides with the center axis; and a controller for
controlling operations of the illuminators, the light receiver, and the
rotating optics, wherein the toroidal mirror reflects light fluxes
emitted from the surface of the sample illuminated by the one or more
illuminators in emitting directions perpendicular to the center axis and
directs each of the light fluxes to the center axis, and wherein the
rotating optics specifies one of the light fluxes reflected by the
toroidal mirror and directs the specified light flux to the incident
aperture of the light receiver.