US Patent 7339681 Surface plasmon resonance microscope using common-path phase-shift interferometry

The present invention integrates the surface plasmon resonance and common-path phase-shift interferometry techniques to develop a microscope for measuring the two-dimensional spatial phase variation caused by biomolecular interactions on a sensing chip without the need for additional labeling. The common-path phase-shift interferometry technique has the advantage of long-term stability, even when subjected to external disturbances. Hence, the developed microscope meets the requirements of the real-time kinetic studies involved in biomolecular interaction analysis. The surface plasmon resonance microscope of the present invention using common-path phase-shift interferometry demonstrates a detection limit of 2×10−7 refractive index change, a long-term phase stability of 2.5×10−4π rms over four hours, and a spatial phase resolution of 10−3 π with a lateral resolution of 100 μm.