Intensity fluctuation spectra of dynamic laser speckle patterns acquired by a full-field temporal modulation method

A method for obtaining the intensity fluctuation spectra of dynamic laser speckle patterns is introduced, which is based on the temporal modulation of the illumination and the subsequent integration of the intensity signals. This approach does not rely on the fast sampling rate to meet the Nyquist criterion, making it applicable for full-field imaging applications. The intensity fluctuation spectra created by the in-plane motion of a random phase object was investigated by using both a single-channel detector and a multichannel sensor. The power spectra obtained by using the full-field temporal modulation method were found to agree with the homodyne Doppler spectra obtained by using the method of autocorrelation and Fourier transform.