Beam Crossing Optical System

About this technology

Overview

NASA's Langley Research Center has developed a Beam Crossing Optical System for use in two-point Focused Laser Differential Interferometers (FLDI) that are used in measuring density disturbances in hypersonic flows. Conventional single point FLDI systems only measure how flow fluctuates. In contrast, with the two-point system, velocity can be measured between the two points to compute spatial changes and measure fluctuating flow. In this design, laser beams propagating between the transmitter and receiver sides of the FLDI instrument remain parallel to one another so that velocity bias errors that occur in the conventional testing region with angled beams are eliminated, increasing accuracy and decreasing uncertainty of sensitivity measurements. The technology offers a lower-cost (half the cost) alternative to a Nomarski Prism approach and enables increased manipulation capabilities for the user, such that the separation distance between points and laser beam orientation can be manually adjusted with ease.