The method description
Infinite width of fringesFor instrument adjusted to infinite fringes width the measurement output represents one interference pattern [1], [2], [3]. This pattern is converted to digital bitmap form and further proceeded:As first processing step we convert this picture, which has by default 256 shades of gray, to the black and white picture. This simple technique consists in selection of gray threshold shade and transformation of all bright points to the white ones and darker to the black ones. Thresholder shade must be selected so, that each interferential fringe must remain continuous and adjoining fringes must not touch each other. The threshold shade is independent on thickness of fringes. For more complex interferograms it is possible to divide the interferograms in some parts and apply this process subsequently on each one, due to difficult threshold setting. Some annomalies may be corrected by hand.Secondly, when explicit differentiations between interferential fringe and surrounding areas are finished, we must distinguish individual areas between fringes. We search subsequently over the whole interferogram and colour each white point or points creating a white area by color not yet used in the bitmap.In the third step we reduce the interference fringes used for separating of areas up to now. Following algorithm can reduce the interferent fringes: By sequential searching in the picture by one direction (e.g. up to down) it looks for all pairs of contiguous points, where the first is black, and the second is of different color. In this process we repaint the black point by the color of the second point. Applying this process subsequently, in four directions (up to down, left to right, down to up, right to left), all black points are reduced. This process reduces the fringes and bound areas encounts in the middle of fringes.
