Segmentation d'images couleur par un opérateur gradient vectoriel ...

QUANTIFICATION ET MORPHOLOGIE DE PHASES DE CLINKER PAR ANALYSE D'IMAGE.
representative for the clinker as the 2000 points manually counted by the expert, which cover a
larger analysis domain.
For the analysis, two different magnifications were tested. The analysis of clinker 1 and 2
used an examination field of 95µm*125µm for each image. The 50 fields of clinker 3 were taken
with a less important magnification. Each image represents a field of 240µm*315µm. This
corresponds to at least 40 crystals. The examination field is about six times bigger than in the case
of clinker 1 and 2. The bigger field represents the clinker more correctly and the examination
points are placed in a higher distance of 13µm.
In the case of the reduced magnification, the dimensions (measured in picture elements)
of each crystal in the image are less important. Thus, automatic colour and texture classification
works with a local window of a smaller size. This decreases the performance of the automatic
classification observed in Table 1. The difference between column a) and b) is more important
for clinker 3 than for clinker 1 and 2.
For the future, the solution will be either to increase the number of images with the
bigger magnification to obtain a statistically significant sample or to increase the performance of
the classification method to obtain good results with a less important magnification.
2.7 CONCLUSIONS
The object of this paper was the automatic quantitative determination of the phases of
Portland cement clinker using a computer imaging system. The applied methods are based on
advanced texture and colour analysis. The automatic segmentation of the phases takes advantage
on the characteristics of local windows. The decision is made using data fusion from separated
colour and texture classifications. The presented software determines the percentage of the main
clinker phases.
The proposed method gives access to the results manually obtained by the expert on
different clinker types. The automatic phase segmentation between alite and belite gives good
results. The system is integrated in a user interface, which makes the clinker analysis easy to be
used even by a less experienced operator. The complete system can use the acquired images
twice. Besides the use for the phase distribution analysis, the images can be used for the crystal
size measurement.
The automatic system is installed in the Lafarge laboratory in Viviers (France) and is used
as a routine tool for the microscopic analysis. It permits to considerably reduce the time needed
for the analysis of the different clinker samples. The system can replace the classical hard and
tiring work and gives new possibilities to the clinker microscopy.
The manual modification of wrong classed points is possible by the open and interactive
software design by a simple mouse click. The corrections can be used to optimise the classifier.
This can be made by adaptation of the parameters used for the texture analysis or by amelioration
of the learning database.
In an additional developing state of the system, the automatic crystal measurement and
form determination will be integrated. This could bring new information about the clinker and
increase the performance of the quality control. Also, the determination of the minor phase
WORLD CEMENT RESEARCH AND DEVELOPMENT 1998 107