Patent ID: 7796256

Claim:
A system for imaging particles in a fluid, the system comprising: a. a flow chamber having a refractive index, the flow chamber including a wall and a channel arranged to transport the fluid therethrough at a selectable rate; b. a light source arranged to illuminate the fluid in the flow chamber; c. a backlighting generator; d. a high numerical aperture condenser to focus backlighting from the backlight generator to the fluid in the flow chamber; e. an immersion oil placeable on the wall of the flow chamber in the area where the light source illuminates the fluid; f. a high numerical aperture objective including a lens placeable in the immersion oil, wherein the high numerical aperture objective is arranged to focus excitation light from the light source onto the flow chamber and to receive incident optical radiation from the flow chamber; and g. means for capturing images of particles in the fluid detected through the high numerical aperture objective.