ABSTRACT
The prerequisite for any vision application is that the features to be analyzed by the computer can be seen in the image. In spite of the rapid progress in sophisticated image analysis algorithms, the performance of the camera and illumination subsystem can greatly affect the reliability and cost of a machine vision application. The vision applications in the fish industry present a real challenge to illumination design. In diffuse backlighting, partly translucent parts of the fish such as the tail and the head have a low contrast in respect to the background. The diffuse backlighting for line scan camera can be implemented by using linear light sources like fluorescent lamps. The transparency of the fish and the specular reflections can cause inaccuracy in dimensional measurements of fishes when diffuse backlighting is used. However, the method is more robust than condensing backlighting that is sensitive to dirt and water drops on a transparent background.
