Submicron feature surface mapping interferometer for hard-to-access locations

This paper describes a compact, imaging Twyman-Green interferometer to measure small features such as corrosion pits, scratches and digs on hard to access objects such as assembled parts. The shoebox size interferometer was designed to guarantee proper orientation and working distance relative to the inspected section. The system also provides an extended acceptance angle to permit the collection at selected view points on a subject. We will describe the various image shifting techniques investigated as part of the prototype. All the components with the exception of power supplies were integrated into an enclosure. The interferometer has been demonstrated to provide sub-micron depth resolution and diffraction limited spatial resolution (a few microns). This paper will present the final performance achieved with the system and provide examples of applications.