System and methods for differential imaging using a lock-in camera

The present invention describes an imaging system that allows visualization of a wide range of samples both in terms of morphology and in terms of material (e.g. density distribution, varying chemical composition, or anything that induces a change of optical path). The application of this imaging system includes absorptive samples as well as nearly and fully transparent samples with respect to the wavelength of illumination. Two elements are key in this system: the use of a so-called lock-in camera, and the synchronization of the recording to a modulation of choice along the image forming apparatus. Such modulation can consist for example in modulation of the illumination, use of filters, tilt/rotation of the sample or of certain microscope components.