Glass particles detection.

Glass discs are used in industrial environment (e.g. laboratory) but also in commercial applications. The production of these glass discs is basically comparable with the production of other commercial available glass products (e.g. drinking glass, beer glass, wine glass).
During production by opening the mold, small glass particles can break off of and get in contact with the hot glass disc.
The glass particles and the hot disc will join together. In the most worse situation large particles with sharp points stay on the disc and can cause some injury.
The small particles results in an unwanted rough surface of the disc.

To detect these small particles with a size of a few pixels is not obvious. All depends of a very good illumination which causes a large contrast.

J.A.I.M.S. Compared two type of illuminations, one the most common illumination method (Standard illumination) used in the most glass vision inspection systems, and a special designed illumination (JAIMS illumination). This special designed illumination is designed for a disc shape and fit to the size of the disc. Using the JAIMS illumination gives the possibility to increase the light intensity so small particles getting more visible without increasing substantially the background noise.
To show the difference between these two illumination types a pseudo 3D plot is also shown.
Schotel B JAIMS Schotel B 3D small JAIMS Schotel D JAIMS Schotel D 3D small JAIMS First image is the camera image created with the Standard illumination, second is the 3D plot of this image.
Third image is also the camera image created with the JAIMS special disc illumination, fourth is the 3D plot of this image.
The white spot are the particles. In the 3D plot of the JAIMS special disc illumination the very small particles are clearly visible and detection is no problem. The Standard illumination shows only the larger particles, the small particles can not be detected.

Im analysed particle Standard illumination and line profile JAIMS illumination and line profile JAIMS illumination and line profile High Int
Here a few sub images including the intensity (line) profile are shown from a particle within the green rectangle.


    First sub image: Standard illumination, 'delta intensity' = max–min = 124–33=91, 'delta relative' = (max–min)/min = 2,76.
    Second sub image: JAIMS illumination, 'delta intensity' = max–min = 72–20 = 52, 'delta relative' = (max–min)/min = 2,60. Even the 'delta intensity' and the 'delta relative' are lower then the image created by the Standard illumination but not it's not a substantially difference.
    Third sub image: JAIMS illumination high intensity, 'delta intensity' = max–min = 251–45 = 206, 'delta relative' = (max–min)/min = 4,58.

After boosting the intensity without increasing substantially the background noise 'delta intensity' and 'delta relative' are increased with respect to the Standard illumination image.
Compare also the standard deviations: 25,5; 15,6 respectively 62,7.

This way of illuminating the glass disc gives the possibility to detect very small particles and results in a higher reliable vision detection system.
And again:

Lighting is the key.

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