FIGURE 1.

Prismless TIRM. Excitation light from an expanded laser beam is focused by a lens on the BFP of the objective. Light is refracted at the objective into a parallel ray propagating toward the glass/coverslip interface. All refracted light is incident on the interface at angles beyond critical angle for TIR. The evanescent light at the interface excites fluorescence at the sample surface that is focused into a narrow cone by the metal film with maximal intensity at θ_m > θ_c and collected by the objective. Fluorescence transmits the filter cube and is focused by the tube lens on the pinhole. A collector focuses light transmitting the pinhole onto the active surface of the APD.