PSI - Issue 77

Francisco Afonso et al. / Procedia Structural Integrity 77 (2026) 584–592 F. Afonso et al. / Structural Integrity Procedia 00 (2026) 000–000

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The employed tracking targets varied according to the method. With the neuromorphic camera and Prophesee lens, two paper bands with parallel lines were attached to the fan’s side, one horizontal and one vertical, to emphasize motion in each direction. For the macro-lens configuration, a grid (0.1 mm thickness lines spaced 2 mm apart) was used with the neuromorphic and image tracking approaches and placed on the same side of the fan, replacing the vertical and horizontal stripes. Finally, with the frame camera and macro-lens setup, a printed grayscale gradient was used as a pseudo-speckle pattern to attempt DIC analysis. Despite not being a speckle pattern by design, at high magnification values, the printer ink resembles one. Figure 2 illustrates each target type.

(b)Grid.

(a) Parallel lines.

(c) Gradient.

Fig. 2: Target types.

Illumination proved challenging; the laboratory is equipped with fluorescent lighting, which introduced intensity oscillations visible in the recordings. Figure 3a shows a dominant 100 Hz frequency detected by the neuromorphic camera, attributable to the lighting oscillation. To mitigate this e ff ect, an incandescent lamp was used to illuminate the fan. The macro lens was set up using a Thorlabs VG100 / M V-Mount Holder, in order to keep such a large assembly stable without damaging the cameras (Figure 3b).

(b) Neuromorphic camera with macro setup.

(a) 100 Hz dominant frequency.

Fig. 3: Setup illumination.