Method for the optical inspection of a transparent protective layer and of a colored patterned surface

A method for the optical inspection of a transparent protective layer and of a colored patterned surface, whereby the transparent protective layer at least partially covers the colored patterned surface, said method using a first source of illumination and a first imaging sensor associated with the first source of illumination, said method comprising the steps of:

• illuminating said protective layer with light emitted by the first source of illumination in order to recognize defective places inside and beneath the transparent protective layer, said first source of illumination emitting shortwaved light in the range that is visible for the first imaging sensor, the light striking said surface penetrating at least partially into the protective layer and scattering at the defective places:
• picking up light scattered back from the defective places with the first imaging sensor;
• and
• recognizing the defective places by the local increase in the intensity of the light picked up by the first imaging sensor in the area of the defective places;
• the light emitted by the first source of illumination being imaged in the form of a line on the surface of the transparent protective layer and the widening of the line caused by the back-scattered light in the area of the defective places being detected on the surface of the protective layer by the first imaging sensor.

A method for the optical inspection of a transparent protective layer and of a colored patterned surface, whereby the transparent protective layer at least partially covers the colored patterned surface, said method using a first source of illumination and a first imaging sensor associated with the first source of illumination, said method comprising the steps of:

• illuminating said protective layer with light emitted by the first source of illumination in order to recognize defective places inside and beneath the transparent protective layer, said first source of illumination emitting shortwaved light in the range that is visible for the first imaging sensor, the light striking said surface penetrating at least partially into the protective layer and scattering at the defective places;
• picking up light scattered back from the defective places with the first imaging sensor;
• recognizing the defective places by the local increase in the intensity of the light picked up by the first imaging sensor in the area of the defective places;
• providing a second source of illumination that emits light at a first wavelength that excites the protective layer to fluoresce with light at a second wavelength that is different from the first wavelength, the fluorescent light being picked up by a second imaging sensor associated with the second source of illumination, and defective places in the transparent protective layer being recognized on the basis of local changes in the intensity of the fluorescent light.

An arrangement for the optical inspection of a transparent protective layer and of a colored patterned surface, whereby the transparent protective layer at least partially covers the colored patterned surface, said arrangement comprising a first source of illumination and a first imaging sensor associated with the first source of illumination, the emission spectrum of the first source of illumination encompassing shortwaved light that is visible for the first imaging sensor, the first imaging sensor picking up light scattered back from defective places inside and beneath the transparent protective layer, whereby the defective places can be recognized by the local increase in the intensity of the light picked up by the first imaging sensor in the area of the defective places, a second source of illumination arranged at a distance from the transparent protective layer to be inspected, the second source of illumination emitting light at a first wavelength that excites the protective layer to fluoresce with light at a second wavelength that is different from the first wavelength, and a second imaging sensor associated with the second source of illumination arranged in such a way that it can pick up the fluorescent light of the protective layer, whereby defective places in the transparent protective layer can be recognized by local changes in the intensity of the fluorescent light.