1. A centrifuge blood processing system for separating fluid components comprising: a separation chamber rotating about a central rotation axis, at least one pump regulating fluid flow in said separation chamber; a light source in optical communication with said density centrifuge blood processing system for providing an incident light beam for illuminating an observation region on said density centrifuge blood processing system, thereby generating light transmitted, scattered or both from said observation region; a light collection element in optical communication with said density centrifuge blood processing system for collecting at least a portion of said light transmitted, scattered or both from said observation region and for directing at least a portion of said light transmitted, scattered or both from said observation region onto a two-dimensional detector; the two-dimensional detector positioned to receive and detect said light transmitted, scattered or both from said observation region provided by said light collection element, as a field of pixels, each pixel having an intensity; a computational apparatus using, for a particular image, a plurality of image processing procedures in series to distinguish one or more phase boundaries, said computational apparatus being programmed with a control program that causes said control apparatus to determine a set of gradients of said pixel intensities, and to assign a value representing a phase boundary to pixel locations for said gradients which exceed adjacent gradients in a selected direction and to assign an intensity representing a phase to pixel locations for said gradients which do not exceed adjacent gradients in said selected direction.