## 3 Experiment Setup  
The indirect ToF camera used in this study is a CamBoard Pico Flexx camera (PMD Technologies AG, Siegen, Germany). This camera contains a 3D CMOS sensor with a resolution of \(171\times 224\), and a field of view of \(62^{\circ}\times 45^{\circ}\). The illumination source on the camera is an 850 nm VCSEL with eye-safe power output and an operating distance from 0.1 to 4 m. This ToF camera comes with a compact form factor of 68 mm \(\times\) 17 mm \(\times\) 7.35 mm and consumes only 300 mW average power, which makes it ideal for mobile application scenarios. In our experiment, the ToF camera is connected via USB to a laptop (2019 Lenovo X1 Extreme), which is used to both control the camera and process the recorded 3D video to extract HR and RR. The ToF camera is mounted on a stand positioned at the same height and \(\sim\)60 cm away from the participants, which allows us to capture a participant's face and chest region in one frame (Figure 1). To provide a reference HR and RR reading, a contact-based finger pulse oximeter capable of recording both HR and RR with accuracy down to \(+/-1\) BPM (Mighty Sat Rx, Masimo, Irvine, CA, USA) is placed on \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Reference** & \begin{tabular}{c} **Wavelength** \\ **(nm)** \\ \end{tabular} & \begin{tabular}{c} **Camera** \\ **Type** \\ \end{tabular} & \begin{tabular}{c} **Avg. HR** \\ **Error (BPM)** \\ \end{tabular} & \
\begin{tabular}{c} **Measures** \\ **RR?** \\ \end{tabular} &
\begin{tabular}{c} **Avg. RR** \\ **Error (BPM)** \\ \end{tabular} \\ \hline
[19] & 675/800/842 & NIR & 0.76 & No & N/A \\
[21] & 940 & NIR & 13.6 & No & N/A \\
[24] & 850 & ToF & 3.46 & No & N/A \\
[29] & 850 & NIR & 2 & No & N/A \\ This & 850 & ToF & 6.25 & Yes & 1.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of recent studies on IR camera-based HR/RR monitoring system. one of the participant's index fingers. All measurements are made under the illumination of fluorescent light (mounted on the ceiling, powered by AC electricity at 60 Hz), no special control of ambient light illumination is applied during the study. To determine the HR and RR of a participant, two ROIs are used to extract HR and RR of the participant (Figure 2): ROI-1 is used for HR extraction while ROI-2 is used for RR extraction. The location of ROI-1 that covers both the nose and cheek is calculated by evaluating the relative position between the participant's eyes and nose with a 66-point facial landmark detection algorithm [33]. The ROI-2 region that represents the upper chest regions is determined from the relative position between the jawline and the shoulder using a pose estimator [34]. Specifically, the system uses both grayscale intensity and depth information from ROI-1 to derive the HR while only the depth information from ROI-2 (upper chest) is used to derive the RR. One advantage of using an indirect ToF camera for physiological monitoring is that it can operate under low or complex ambient light conditions. The enhanced immunity against external lighting conditions is a result of the narrow band-pass filter (centered at 850 nm) placed in front of the optical lens as well as the background illumination suppression from the detection mechanism used in the indirect ToF camera [30]. To demonstrate the benefits of being independent of ambient lighting in physiological measurements, we show the results of HR measurement under various lighting conditions: a dark environment, a bright environment, and an environment where ambient light is switched on/off periodically. Figure 3 shows the (a) raw intensity from ROI-1 when measured under the dark/bright environment and the (b) corresponding frequency domain information. When measuring under the dark environment, all ambient lights are switched off and the background illumination is reduced to <1 Lux. When measuring under the bright environment, in addition to the ambient fluorescent lighting, an 100 W halogen lamp is placed 1 m from the participant to create an illumination of 960 Lux.