Tracker Module

The framework for the Multi-Worm Tracker is shown in Figure 1.

Figure 1: Framework of the Tracker

The tracking system is automatically initialized by the detector in the first two frames. For separate worms, the single-worm tracker is used. When two or more worms come into contact, the multi-worm tracker is initiated. Both trackers are based on a particle filter. Figure 2 shows 100 particles (predictions of the current state: axial progression and radial displacement) at one frame, and Figure 3 shows the two observation models used for computing the likelihood of particles. The region-based observation model computes likelihoods based on inward and outward intensity information, while the edge-based observation model uses the distances between the model points and detected edge points.

Figure 2: 100 particles of one worm at one frame (the head part has a larger amplitude of displacement)

Figure 3: Observation models

After tracking, the center line of the worm will be further adjusted, as shown in Figure 4.

Figure 4: Center Line Adjustment based on 1D Filtering

We made several modifications for the multi-worm tracker. For more details about its differences from the single-worm tracker, please refer to:

• Report for the Tracking System