Rotation-invariant recognition of copepods by circular harmonic filters.

The traditional identification of copepods is exhausting and time consuming. Perhaps that is the reason why in recent years the number of competent taxonomists has decreased significantly. Researchers have tried to automatize the identification process of marine microorganisms, but they have problems with the quality of the images and the orientation of the organisms. Rotation-invariant circular harmonic filters are generated in a computer, the computation time can be improved and the computer can work indefinitely. Three types of circular harmonic filters were studied in older to recognise and count copepods despite their orientation: Classical, phase only and multiple. Classical circular harmonic filters discriminated genus, species and sometimes sex, depending on the complexity of the organism. Phase only circular harmonic filters always differentiated among sexes. Multiple circular harmonic filters discarded false detections. The three types of circular harmonic filters recognised the target organism among others in a test image, so inexperienced observers can use them.