Recognising blood cells presents a big challenge for automated counting systems. As blood flows through veins, the cells are deformed in the direction of blood flow. Blood also contains a lot of other 'junk' material such as proteins. Computers find it difficult to recognise the cells once they have been deformed against this background 'junk' and therefore require a large number of 'templates' of each different cell shape.

The Sysmex system shines a laser onto a part of the body that has blood vessels close to the skin, for example an earlobe, lip or finger. A set of fibre optic cables collects the light reflected from the blood vessel and pipes it to an image intensifier. This signal is then sent to a CCD camera and analysed on an Apple Mac computer in real-time. The computer converts the captured image into a two dimensional grid and a mathematical algorithm is used to determine if a particular object is a blood cell or not. Rapid analysis of the blood passing through the system then allows the computer to calculate the number of cells in the blood.