2015-05-042015-05-042003-12-16Mittleman, Daniel M. and Johnson, Jon L., "Interferometric imaging system and method." Patent US6665075B2. issued 2003-12-16. Retrieved from https://hdl.handle.net/1911/79858.https://hdl.handle.net/1911/79858A broadband imaging system is disclosed that provides greatly enhanced depth resolution through the use of phase shift interferometry. The system may comprise a transmitter, a splitter, a phase inverter, and a receiver. The transmitter transmits a signal pulse that is split into a measurement pulse and a reference pulse. The measurement pulse is applied to a sample, and a relative phase shift of approximately π radians is introduced between the measurement pulse and the reference pulse by the phase inverter. The measurement and reference pulses are then recombined to form a combined pulse that is detected by the receiver. The phase inverter may be a simple lens that introduces a Gouy phase shift by passing the measurement or reference pulse through a focal point. In this manner, a background-free measurement is provided, which provides a greatly enhanced sensitivity to small changes in the measurement waveform, regardless of origin.16 ppengUtility patentUS6665075B2