## 2 Materials and Methodology
### Image Acquisitions  
Images are acquired using a snapshot HSI system (Hyperea, Quest Medical Imaging B.V., Middenmeer, The Netherlands). The camera and the spectral response are visualized in Figure 2b,c. Each wavelength is covered with narrow spectral response bands to reach a high spectral resolution. The main characteristics of the camera are summarized in Table 1.  
The camera, running at 16 fps, captures 41 spectral bands in one snapshot, which are equally distributed in the visible near-infrared (VIS-NIR) range of 450-950 nm. The experimental set-up consists of a charge-coupled device camera (CCD) and three sensors--RGB, VIS and NIR--of which two are mosaic spectral sensors and one is a spectrally optimized lens. For 2D reference, a high-resolution color image is included with each HS dataset. The color image is co-registered with the HS data with subpixel accuracy, facilitating accurate data fusion and visualization methods. The two mosaic sensors have a \(4\times 4\) filter pattern for the VIS range and \(5\times 5\) pattern for the NIR range in order to build an HS snapshot system. Each HS image acquisition leads to a data cube with a spatial resolution of 1080 \(\times\) 2048 and 41 spectral bands after processing. The HS camera is based on a tiled-filter approach (Figure 2d), where pixels are individually filtered with narrow Fabry-Perot bandpass filters. This method allows imaging without the need to scan in either the spatial dimension (e.g., moving the  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Spectral Sensitivity** & \multicolumn{2}{c}{**Mosaic Sensor**} & \multicolumn{2}{c}{**Images**} \\ \hline Spectral range & 450-950 nm & VIS (Visible) & \(5\times 5\) & Resolution (upscaled) & 2048 \(\times\) 1080 px \\ Number of bands & 41 & NIR (Near-infrared) & \(4\times 4\) & Resolution spectral image & \(\sim\)500 \(\times\) 250 px \\ Average bandwidth & \(\sim\)12 & & Frame rate & 16 fps \\ \hline \hline \end{tabular}
\end{table}
Table 1: Hyperspectral camera characteristics.  
Figure 2: (**a**) Schematic view of the hyperspectral imaging (HSI) camera setup. (**b**) Plot of the spectral response of the camera, where the different lines correspond to the individual channel responses. Similar to an RGB camera with three filters for each color pixel, in a snapshot HS camera, each sensor is composed of several pixels that are responsive for a wavelength in the band spectrum. (**c**) Experimental prototype of the snapshot HSI camera. (**d**) Mosaic sensor technology. The picture describes a tiled-filter approach where different wavelengths are captured for different cavity heights.  
camera) or to change the pass-through characteristics of an optical filter. To uniformly illuminate the field of view, the camera was mounted on a tripod with a 500 W 240 V halogen light (Philips Lighting B.V., Eindhoven, The Netherlands) fixed 10 cm above it. In this study, the distance between the camera and the subject was 20 cm, resulting in a 15 \(\times\) 15 cm field-of-view (Figure 2a). For every acquisition, the time required is approximately one second. However, in the current setup, a postprocessing step is required to construct the HS data cubes. A schematic view of the experimental setup is visualized in Figure 3.