Disclosed methods and systems may be operable to obtain non-contact diagnostic information about movements of scattering objects such as fluids in subsurface vasculature in tissue. As an example, a method may include causing a light source to illuminate the tissue with at least a first portion of the emitted light and illuminate an optical modulator with at least a second portion of the emitted light. The second portion of the emitted light may be modulated by the optical modulator. An offset source is configured to provide an offset frequency signal. An image sensor may receive optical information from the sample. A heterodyne signal based on the reference frequency signal and the offset frequency signal may be used as a gain input of each detector element of the image sensor. Based on the received information, a movement of a portion of the sample may be determined.
