A method includes attaching two or more beads to each unit of one or more units of a chemical component in a sample, to form, for each unit of the chemical component, a multi-bead complex including two or more beads and the unit of the chemical component; placing the sample on a surface of an image sensor; at the image sensor, receiving light originating at a light source, the received light including light reflected by, refracted by, or transmitted through the beads of the multi-bead complexes; at the image sensor, capturing one or more images of the sample from the received light; and identifying, in at least one of the images of the sample, separate multi-bead complexes, the identifying of the separate multi-bead complexes including associating the two or more beads of each of the multi-bead complexes based on proximity to one another.