Design and validation for laser based scanning reflectometer

Abstract

Scope and Method of Study:

The goal of this study was to design and validate laser based scanning reflectormeter. This senor generates information indicative of spectral reflectance characteristic of the small spot. The information indicative of the spectral reflectance characteristic can be used to determine the object in the field. Light emitted from the optical source is modulated so that reflected light from the source can be discriminated from the reflected ambient light. The influence of detector location, source location and uniformity of reflectance across the swath width were characterized.

Findings and Conclusions:

The calibration constant was developed as a function of sensor height, incident angle, and detector area. Results of uncertainty analysis indicate that incident angle and detector area rapidly effect the measured reflectance. The second design with off-axis parabolic reflector is capable of achieving the design objectives. The average predicted reflectance values along the swath width were 50.26% and 42.97% for red and near-infrared correspondingly. This design indicated that uniform illumination (reflectance) across the swath width and height invariant reflectance can be obtained. In order to design a sensor, which is capable of producing uniform illumination across the swath width and produce height invariant reflectance following specifications must be met, the surface quality of the scanning mirror must be at least 60-40, the detector and source must be perpendicular to the target object.