System, devices, and methods for digital holography

A digital fresnel reflection holography (DFRH) probe comprising:

• an input configured to receive incident light;
• a beamsplitter positioned to receive light from the input and to direct light perpendicularly to a sample through an imaging window located in front of the sample, and to receive reflected light from an imaging window, wherein reflected light includes a reference wave reflected from the imaging window located in front of the sample and a backscattered wave reflected from particles within the sample;
• an objective lens positioned to focus reflected light provided to the beamsplitter;
• and
• a camera positioned to capture a two-dimensional (2D) hologram based on the reflected light.

A method of imaging particles, the method comprising:

• directing a collimated light beam to a beam splitter, wherein the beam splitter directs the collimated light beam to a sample through an imaging window located in front of the sample, wherein the collimated light beam is directed perpendicular to the imaging window;
• directing reflected light received from the imaging window to an objective lens and an imaging camera, wherein the reflected light includes a reference wave reflected from the imaging window located in front of the sample and a backscattered wave reflected from particles within the sample;
• and
• storing 2D holograms captured by the imaging camera.