A different type of equipment employs a sensor located above a conveyor
belt, which views products as they pass beneath. The sensor detects up to eight
colours and provides an alarm or control signal whenever a pre-selected colour
passes the detector beam. It is also able to distinguish between different
coloured foods which are to be processed separately. In a more sophisticated
system, foods which have variations in colour over their surface are colour
sorted by image processing. The foods are fed in rows on a roller conveyor
beneath a video camera. The relative intensities of reflected red, green and
yellow light are transmitted to the microcomputer which constructs a composite
image of each piece of food, showing both the spread of colour and the mean
colour of inspected foods. The computer compares the constructed image with
pre-set specifications and activates a compressed air ejector or a mechanical
deflector to remove rejected food. When this type of system is used to sort
baked goods, it is also used to control directly the gas or electricity supply to
the ovens, which is reported to reduce energy consumption in ovens by 20%.
The sorter can be easily adapted to different foods, by operators using the
microprocessor keypad.