Digital holographic microscopy and related image processing techniques are described. A hologram captured in an image frame is split into different depths while a new hologram is being captured. Image slices of the hologram are determined and using free space impulse responses that are pre-calculated at a different precision than processing operations using the holographic data. Each computation is calculated in parallel based on the number of available processing cores and threads. The image slices are combined into a 2D array or 3D array to permit further processing of the combined array to count and size particles in the image frame. The reconstructed hologram is displayed at a subsequent image frame than that used to capture the hologram.