Researchers at the University of California, Berkeley have developed an invention that consists of an angular interferometer able to measure angle variations of a coherent, collimated light source with an accuracy below 30 nrad. The optical setup is compact and consists of a few simple optical components. The novelty of this innovation lies in the use of a simple, cost-effect technique to amplify the sensitivity of the instrument. The disclosed invention is in principle capable of being integrated into more compact, high-sensitivity commercial instruments for a fraction of the cost of current, state-of-the-art instruments (currently exceeding $30,000). Commercial devices used to measure the angular deviation of a single beam include autocollimators and interferometers. The highest resolution offered by a commercial system is 25 nrad. The disclosed angular interferometer is able to measure relative angle variations (of a sample beam relative to a reference beam) below 30 nrad, though the resolution is known to currently be limited by the specific details of the current application and can therefore be further reduced with minor, inexpensive improvements.