| abstract |
An apparatus for analyzing the presence of a single molecule comprises a sample plate (30’) having a sample located thereon. In one embodiment the apparatus comprises two lasers (46’, 46’’) for providing illumination light at two different wavelengths suitable for exciting fluorescence in the sample, a collimator comprising a band-pass filter (50’, 55’’), a diverging lens (54’, 54’’), a field stop (62’), and a converging lens (66’) for directing the illunination light through a total internal reflection objective (74’) onto the sample, and means (34’, 34’’) for detecting a fluorescent image produced by said sample in response to the illunination light. In one embodiment the apparatus further comprises an auto-focus module comprising a laser (38’), a beam splitter cube (86’), a converging lens (90’), and an auto-focus dichroec (94’) for maintaining focus of the objective on the sample. |