Ellipoidal Mirror Reflectometer Including Means for Averaging the Radiation Reflected from the Sample

An ellipsoidal mirror reflectometer for measuring the reflectance of materials includes a source of monochromatic light, an ellipsoidal mirror reflector with an aperture therein, a specimen support position at the first focal point of said reflector, means for directing the monochromatic light through the aperture onto the support, and an averaging sphere detector positioned adjacent a second focal point of the reflector, the first and second focal points being on a common axis normal to the first focal plane of the reflector