Infrared digital holographic imaging

A digital holographic technique has an extended measurement range and improved resolution at infrared wavelengths. Long-wave interferometers have been widely used in many applications, including infrared (IR) optics, IR transmitting ma-terials, and high-reflective multilayer dielectric coatings for high-power laser systems.1–3 In the field of metrology, re-searchers have focused on longer wavelengths because they greatly extend the measurement range of interferometric techniques. However, one significant drawback of longer wave-lengths is that they decrease resolution, and existing technolo-gies for IR interferometers, such as pyrocam arrays, are limited by low spatial resolution. Other methods to extend the measurement distance employ longer synthetic wavelengths4 (the beat wavelengths between two different wavelengths). In thesemethods, several hologram