An imaging device (46) comprises a carrier stage (12a) for carrying a sample slide (14a) including a micro-array of cellular binding event samples, a linear light source (37a) for illuminating the sample slide (14a), and a motor drive (16a) for moving the carrier stage (12a) relative to the sample slide (14a) such that successive portions of the sample slide (14a) are illuminated by the light source (37a). A digital opitical line scan camera system (44a) is disposed such that, in use, it captures substantially only the successive portions of light rays (40a) which emerge from the sample slide at an offset angle relative to light rays (42a) from light source transmitted through and emerging from the sample slide (14a) to generate a series of linear dark field images arranged to be reconstructed into a composite image of the sample slide or array of samples.