Direct measurement of nanometric displacement under an optical microscope

A novel method has been developed to measure nanometric displacement under a conventional optical microscope. The magnified image of a pinhole was divided into two parts using a prism-shaped mirror. The difference of light intensity between the divided images was determined, which was proportional to displacementof the pinhole. Using a 5-microm diam pinhole, the accuracy to determine displacement was ~1 nm. Instead of a pinhole, polystyrene microbeads were used in the new method. Displacement of the microbeads was also measured with nanometric accuracy. This technique could be used to probe nanometric phenomena using optical microscopes.