Two-color differential dynamic microscopy for capturing fast dynamics.

Differential dynamic microscopy (DDM) is increasingly used in the fields of soft matter physics and biophysics to extract the dynamics of microscopic objects across a range of wavevectors by optical microscopy. Standard DDM is limited to detecting dynamics no faster than the camera frame rate. We report on an extension to DDM where we sequentially illuminate the sample with spectrally distinct light and image with a color camera. By pulsing blue and then red light separated by a lag time much smaller than the camera’s exposure time, we are able to use this two-color DDM method to measure dynamics occurring much faster than the camera frame rate.