Austen 

This project presents a novel imaging interferometer to capture airflow density, temperature, and composition information using a grid-patterned fringe structure. This capability is needed in aerospace testing, where high-resolution and frequency data are needed about the test aircraft. At the same time, imaging/optical systems have the advantage of not interfering with the test aircraft, instead being placed outside of the observed airflow. Typical shear-type interferometers are limited to being able to capture information from one direction. In this project, more than one Wollaston prism is used, oriented at an angle to each other, typically 90 degrees, creating a novel grid pattern capable of gathering information from two directions. This paper aims to demonstrate the setup and evaluate the sensitivity and possible analysis techniques that would come with such a system. To explore this concept, a collimated HeNe laser system was used, focused on two large 3-inch Wollaston prisms. The placement of optics and sensitivity of the grid system was tested using cylindrical optics, which generate optical disturbances similar to those that would be created by airflow changes in one direction. Preliminary results from the grid interferometer show the creation of a dense fringe grid with typical sensitivity, but in multiple directions. Although the grid interferometer does provide increased amounts of information, there are difficulties in processing the image when fringes shift exactly perpendicular to the grid. Nonetheless, the grid interferometer setup provides significantly more information, allowing for airflow temperature and density gradients to be gathered in multiple planes.