# Automated Cart with VIS/NIR Hyperspectral Reflectance and Fluorescence Imaging Capabilities
## 3 Results and Discussion
### Camera and Laser Mount Design  
There are a number of considerations for mounting the camera and laser given that these components do not share a common aperture and are being used in a line-scan mode. First, the laser and camera can be mounted so that the illumination and imaging fields are on intersecting planes or on a single plane. For both configurations, the illumination field and the imaging field will only fully overlap for a limited range of focal distances (Figure 4). One advantage of single plane configuration is that the imaging field will always be at the center of the illumination field, so changes in the focal distance will not alter the effective illumination intensity given a uniform intensity along the center axis of the illumination profile. In contrast, when using the intersecting planes configuration, illumination intensity is a function of the focal distance. Another advantage of the single plane configuration is that the usable range of focal distances can be expanded by increasing the length of the illumination profile relative to the imaging profile. A second consideration is whether to mount the components in parallel, or with one or both components at an angle. This consideration is complicated by the limited choices in the selection of Powell and camera lenses. Given the constraint that the desired imaging field of view should be 1.5 m and the height of the components above the ground should be less than 3 m, the best choices are a 30\({}^{\circ}\) Powell lens and a 16 mm camera lens. With this selection, if the components were to be mounted in parallel, the illumination field would slightly smaller than 1.5 m. It was decided to mount the camera perpendicular to the ground and to angle the laser so as to stretch the illumination field. Figure 5 shows this mounting arrangement. Figure 6 demonstrates the equations used to calculate the offset and angle of the laser that would allow the illumination field to be 1.5 m. The final design  
Figure 4: Alignment of imaging and illumination fields as a function of distance from the optics and the positioning of the laser relative to the camera. Figure 3: Torque-speed chart for the stepper motor (Oriental Motor U.S.A Corp.), the red line indicates the maximum torque the stepper motor can produce at 22.33 rev/min when powered by 24 VDC. called for the components to be separated by 105.1 mm at an angle of 2.0\({}^{\circ}\). This positioning produces overlapping 1.5 m fields when the components are mounted 2.74 m above the ground at an angle of 12.2\({}^{\circ}\) relative to fully vertical. The components were mounted at an angle relative to fully vertical for stability, i.e., so that the center of gravity remained within the wheelbase if the cart were to transverse a small incline. Figure 5: Orientation of the camera and laser on the aluminum mount. The distance b between the laser and camera is 105.1 mm and the angle (\(\theta_{\text{Laser}}\)) is 2.0\({}^{\circ}\). Figure 6: Imaging and illumination fields and equations when the camera lens’ center is assumed to be at the origin. The laser lens’ center is assumed to be along the \(y\)-axis and at an offset b from the center of the camera lens. Note m\({}_{1}=\tan(\theta_{\text{lens}}/2)\), m\({}_{2}=\tan(-\theta_{\text{lens}}/2)\), m\({}_{3}=\tan(\theta_{\text{laser}}+\theta_{\text{Powell}}\ /2)\), and m\({}_{4}=\tan(\theta_{\text{laser}}-\theta_{\text{Powell}}/2)\) with \(\theta_{\text{laser}}\) being the angle of the laser relative to the camera. Angling the laser relative to the camera produces a non-uniform illumination intensity profile along the major axis of the illumination. Figure 7 shows the calculated relative distortion in illumination. While it is possible to mathematically correct images for this distortion, this is probably not warranted as the variability introduced if this distortion if ignored is small compared to the response differentials that would be expected for fecal contaminates. Figure 8 shows the camera and laser mounted on the cart.