1. A method of characterizing a parameter of a sample by holographic microscopy, comprising the steps of: receiving multicolor holographic image data of the sample from a storage medium; determining a first estimate of the number of objects in the holographic image data, each object associated with a set of concentric bright and dark rings; determining, for each set of concentric bright and dark rings, by a voting algorithm, a centroid defined by an approximate x, y position in a plane, with each pixel of the image data voting for pixels in a transformed image that may be centroids; determining an estimate of the axial position (z) of each of the objects; determining by Lorenz-Mie analysis an estimate of each of the objects' radius, refractive index; using holographic image data from the sample to characterize properties of the sample and generate information characteristic of the parameters of the sample; and comparing the holographic image data with control holographic image data corresponding to an uncoated sample and determining if the sample has a coating.