Development of a second generation portable specular reflectometer

The second generation design of a portable specular reflectometer is discussed. The instruments respond linearly (+-0.006 transmission units) to variations in the intensity of incident and reflected beams and the readings are not affected by the presence of stray light. As a result of this feature, the reflectometer is well suited for outdoor field use in a normal sunlight environment. A drift problem due to temperature was observed in the detector/preamp at temperatures 100 F. A major improvement in the second generation reflectometer is the use of larger optics to allow averaging over a greater surface area of a mirror. The reflectometer has the capability of a straight through beam configuration, allowing direct determination of the signal level corresponding to 100% reflectance. This capability also allows the user to measure the specular transmittance of materials. A microprocessor can be added to the output of the detector as an option to display percent reflectance values and mean and standard deviations of measurements made.