ABSTRACT
This chapter discusses detection by light, visible or infrared, and leave out picture processing. Automatic detection will probably also use mostly optical techniques, although acoustics or X-rays may possibly be used in combination with optical methods. The chapter looks at optical absorption on its own, it is clear that a substantial portion of500-1200 nm light penetrates through a fillet. Observations through optical band filters of different wavelengths show that a worm on the surface stands out most clearly in violet to green light. Automatic sorting of fillets and other fish products according to the number of quality defects they contain is the next logical step toward fully automatic fish processing. This will require reliable and practical methods for detection of the various kinds of defects in fish flesh. Herring muscle shows considerably higher scattering than cod. Light at the wavelengths involved in the fluorescence processes is, according to the results of the present work, strongly scattered.
