Classifying microbeads in near-field imaging

A method comprising

• placing a sample at a surface of an imaging sensor, the imaging sensor comprising a two-dimensional array of photosensitive elements,
• the sample including (a) microbeads, at least some of which are attached to units in the sample, (b) and target elements, at least some of which are attached to the units attached to the microbeads,
• holding the sample statically within a near-field distance of the photosensitive elements,
• using the imaging sensor to capture a two-dimensional image of the statically-held sample including the microbeads,
• counting the microbeads belonging to each of two different classes in the two-dimensional image, or identifying locations of the microbeads of each of the two different classes in the two-dimensional image, or both counting the microbeads belonging to each of the two different classes and identifying the locations of the microbeads of each of the two different classes, and
• based on at least one of the count of the microbeads belonging to each of the two different classes and the locations of the microbeads of each of the two different classes, performing at least one of an assay, a count, a classification, and an analysis of the target elements in the sample.