The optical inspection system

When dealing with irregularly shaped objects, uniform, diffuse illumination is required to nrininrise highlights and shadows, since these would obviously detract from the measmement of trae surface reflectivity. To eliminate shadows and highlights at the point of measurement, the particle should be surrounded by a spherical surface of uniform brightness. However, in practice this is just not possible due to the following constraints  

To allow a path for particles through the optical inspection chamber, there must be entry and exit points. 

The position of the optical components will result in areas of different brightness, compared with the main chamber wall. 

The use of light sources of finite size leads to non-uniform illumination. 

Specular reflection is almost always a problem, even with a perfect diffuse illumination sphere. If a particle with a diffuse reflective surface is placed in such a sphere, then its trae colour will be observed. However, if the particle surface is not diffuse, specular reflection will occm, giving highlights which do not exhibit the true colour of the surface. Clearly the higlilights can adversely affect the optical system and consequently result in the incorrect classification of a particle. 

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The key point about assessing and defining process and product state similar to the machine operators way, is having objective information about the product quality. In the presented approach, the information from the optical inspection system was used to define characteristic situations based on the profile quality (the kind, distribution and quantity of defects) and the process parameters measured and stored by the automation system. A situation or case is thus characterized, among other things, by the aforementioned profile quality, the kind of profile that is produced, the used rubber-mixture, environmental data like air pressure or humidity, the values and latest progression of physical process parameters hke extruder-temperature, power of microwave heating or speed of conveyor-belts and the countermeasures that are taken by the machine operators. 

It may well be necessary to adapt an optical inspection system to accommodate the three-dimensional layout of MID process surfaces. Class 2l D MID can be inspected without additional kinematics and adaptation of the optical inspection system. This holds true only if the process surfaces are plane-parallel in the inspection plane of the sensor array. Classes n x 2D and 3D call for changes to the AOI system if the electronic components are widely spaced. This could well mean integrating an extra handling and positioning unit for MID, for example an automated workpiece carrier. 

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