Wide-field goniometer for spectroscopic measurement of albedo in laboratory and field. The goniometer (1) comprises an azimuth ring (2) calibrated 0 to 360° at intervals of 1° and horizontally disposed at an elevation and mounted on legs (3) and a first zenith arch (5) calibrated 0 to 90° in one segment and 90 to 0° in the other segment at intervals of 1° . The first zenith arch is vertically disposed and slidably mounted on the azimuth ring at the ends thereof. The first zenith arch is slidable on the azimuth ring at intervals of 1° to match with the calibrations on the azimuth ring and has a light sensor (6) slidably mounted thereon adapted to slide at intervals of 1°. A second zenith arch (7) calibrated 0 to 90° in one segment and 90° to 0° in the other segment at intervals of 1° is vertically disposed above and coaxially with the first zenith arch and is detachably mounted to the first zenith arch at the centre thereof along the 90° calibration on the first zenith arch. The second zenith arch has a light source (8) and a sun finder (9) slidably and detachably mounted thereon to slide at intervals of 1° to match with the calibrations on the second zenith arch. The zenith arches have common centre at 90° with the azimuth ring (Fig 1). The goniometer provides inestimable combination of precise light source and light sensor angular positions so as to obtain very high resolution and accuracy of reflectance values or albedo so as to characterise a test sample very accurately. It is also simple in construction, compact, cost effective and level adjustable to obtain planimetric accuracy of measurements.
Indian patent application no. 1315/MUM/2012
Inventors: D Ramakrishnan