## 2. **Breadboard Design and Implementation**
### 2.1. **Breadboard Architecture**  
The architecture of the breadboard consisted of the computer laptop, the camera plus the camera controller, the image sensor, the optics, the temperature sensor, and the temperature controller, as shown in Figure 1.  
All components used in implementing the camera breadboard are COTS devices. The selected image sensor was an Aptina MT9J001 monochromatic CMOS sensor of 10 megapixels (MP). This sensor is similar to the one proposed by the APST STR [6]. The specifications of the sensor are presented in Table 2.  
Figure 1. The architecture of the breadboard.  
The image sensor relates to the Arducam USB2 Camera Shield, which is the camera control board. The sensor is connected to the Arducam by a 30-pin ribbon cable in the secondary camera interface. The chosen lens is a Fujian, with an \(f_{number}\) of 1.6, a parameter value suggested by the literature, and a focal length of 35 mm. Therefore, the system's \(FOV\) is given by:  
\[FOV=2\left(\frac{h_{sensor}}{f}\right) \tag{1}\]  
In (1), \(h_{sensor}\) is the sensor's active image size and \(f\) the focal length. Thereby, the \(FOV\) of the system is 10.5 deg horizontally and 7.5 deg vertically. Thus, the circular \(FOV\) is given by [17]:  
\[FOV_{circular}=\sqrt{\frac{FOV_{horizontal}FOV_{vertical}}{\pi}}\times 2 \tag{2}\]  
Then, the circular \(FOV\) of the camera is about 10 deg, which is within the values recommended by the literature. Moreover, the \(f_{number}\), which denotes the photons that cross the lens, is calculated by the ratio between the focal length \(f\) and the diameter of the system's aperture \(d\):  
\[f_{number}=\frac{f}{d} \tag{3}\]  
Considering (3), it is possible to calculate the lens aperture, which is 22 mm.
* Mechanical design  
An optical system is very sensitive, and minimal disturbances can lead to errors in the acquired data. So, a mechanical system was designed to maintain the optics as stable as possible. This mechanical design was done in SolidWorks and then 3D printed. The design was developed to place the optical and temperature systems on the same breadboard. The outcome is shown in Figure 2.  
The temperature system is made of aluminium parts produced in a CNC-milling machine. The remaining parts of the platform were 3D printed. The sensor and Arducam are inside the platform. The lens is connected to the sensor by a c-mount adaptor, and the  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Properties** & **Specification** \\ \hline Active image size & 6.440 mm (H) \(\times\) 4.616 mm (V) \\ \hline Resolution & 3856 \(\times\) 2764 pixels \\ \hline Pixel size & 1.67 \(\times\) 1.67 \(\upmu\)m \\ \hline SNR\({}_{\text{MAX}}\) & 34 dB \\ \hline \hline \end{tabular}
\end{table}
Table 2: Aptima MT9J001 specifications.  
Figure 2: Mechanical design and assembled breadboard.  
structure that involves the lens has the purpose of fixating the focus. The optical system is connected to a computer, which controls the camera.  
The temperature system has a temperature controller, a temperature sensor, a thermoelectric cooler (TEC), a heat sink, and aluminium pieces. The temperature controller is connected to an external power supply and the computer. This device sends a programmed temperature to the TEC, cooling the aluminium pieces and, consequently, the optical sensor. The temperature sensor measures the temperature of the CMOS sensor.