A flow cell and use thereof

A flow cell, for analysing objects (e.g. plankton, bubbles and detritus) in a liquid stream, comprises a body 204 having a chamber 206, defined by an inner surface, an inlet 208 and an outlet 210. The inlet comprises a first coupling member 220 having a flow passage 222 and the outlet comprises a second coupling member having a flow passage. The flow cell body comprises a first transparent portion 240, through which light may enter the chamber, and a second transparent portion 250 through which objects within the chamber can be imaged. The chamber comprises a first transition portion 270, providing a smooth transition between the flow passage of the first coupling member and the chamber, and a second transition portion 280, providing a smooth transition between the chamber and the flow passage of the second coupling member. An imaging apparatus and an illuminating apparatus is included for use with the flow cell. The liquid in the chamber is illuminated through the first transparent portion. The illuminating apparatus comprises a light source, a first collimator comprising a pin hole through which the light is passed, and a second collimator comprising a telecentric lens.