An optical diagnosis and analysis system is developed to in-situ observe and estimate crystal growth situation. A polarizing filter and a high pass binary amplitude filter are used in a common microscopy to observe the phase object and also to inverse the image contrast and strengthen the image edge. Meanwhile, a series of image processing techniques, such as median filtering, Robert operator, optimal threshold method and so on, are introduced to analyze the images of the crystal. An improved Hough transformation is carried out to get the pattern of crystal lattice. Finally, according to the integrity of crystal lattice and the evenness in the crystal lattice, some advice on the crystal growth situation is given. Experimental results with the acquired images demonstrate that the proposed system is feasible.
A spatial filtering method was developed for in-situ observing crystal growth and concentration variation. We insert a polarizing filter between the growth chamber and objective lens for eliminating the transmitted light through the solution. The dark background introduced by polarizing filtering method is advantaged for observing the sample. Due to the birefringence property, the image of crystal is contributed by extraordinary-ray and ordinary-ray through the crystal and analyzer. Meanwhile, a high pass binary amplitude filter is inserted on the back focal plane of the objective lens for attenuating low-frequency information and transfer phase information of the object to intensity information of the image. The image intensity has become squarely related to the phase shift φ of the crystal and solution. It is possible to observe the phase object and also to inverse the image contrast and strengthen the image edge. The method has been successfully used to observe not only crystal morphology and details but also concentration field variation around the growing crystal.