... | ... | @@ -22,7 +22,7 @@ The convolution method is fast in computation, but requires high contrast image |
|
|
|
|
|
### 1.2 Detection of the particles from UV light imaging
|
|
|
|
|
|
Though used most commonly in granular studies, discs are far from grains in reality. Hence there have been numerous studies on granular systems with different shapes other than discs, e.g., ellipses, polygons and star-shape-like particles. Here we choose star particles as an example to illustrate how to detect them from UV light imaging.
|
|
|
Though used most commonly in granular studies, discs are different from shapes of grains in reality. Hence there have been numerous studies on granular systems with different shapes other than discs, e.g., ellipses, polygons and star-shape-like particles. Here we choose star particles as an example to illustrate how to detect them from UV light imaging.
|
|
|
|
|
|
With the particle positions and radii information, orientations can be found in the `U' image. Using the blue channel of the `U' image, e.g. Fig.~\ref{fig-diskori}(a), an adaptive threshold is applied locally to binarize the image so that the UV bars are 1 (bright) and the rest of the particle is 0 (dark), as shown in Fig.~\ref{fig-diskori}(b). Then a least squares fit with the minimized perpendicular offsets reveals a linear function between the x and y positions in each UV bar, shown in Fig.~\ref{fig-diskori}(c). The slope of the line gives the orientation associated with each particle.
|
|
|
|
... | ... | |