ROUGHNESS ANALYZER

A device for measuring surface irregularities of an optical surface. A light source strikes the surface to be tested and is both specularly reflected and scattered outside the specular direction. A reflecting cone directs some of that light outside the specular direction to a measuring device. Some of the scattered light falls on the device without striking the cone, as does the specularly reflected light. Thus the fraction of the reflected light which is within a given angle of the specular direction may be measured. Alternatively a light source passes through a hole in the back of a Coblentz sphere. Light within the specular direction returns through the hole and is measured with a light measuring device while light scattered without the specular direction is measured by a second light measuring device.