Z-stacking and Particle Edge Stitching

Z-stacking

If required the system can perform z-stacking so images of each frame are taken at different focus positions and combined together before the particles are separated from the background. This allows large particles to remain in focus and also ensures that any small particles that for example may be in the well of a filter paper (after filtration through a mesh) are counted. Figure 1 shows a section of a frame containing a fibrous particle with and without z-stacking.

Figure 1: Sections of a field of view frame without (left) and with (right) z-stacking

Particle Edge Stitching

If particles cross two or more frames, as is typically the case for fibers, the software identifies the frames which contain the particle image and effectively stitches the pieces of the particle together and then extracts the whole edge stitched particle from the background. It then calculates all of the morphological parameters for that particle image as shown in figure 2. The particle shown is longer than 4 mm and has been extracted from several frames and then edge stitched together. Without particle edge stitching the longest particle to be certain of detecting with the 10X magnification was 420mm.

Figure 2: Field of view images of a particle overlapping several frames and the resulting edge stitched image with particle details. Note length of fiber is 4.1mm