# A Real-Time Remote Respiration Measurement Method with Improved Robustness Based on a CNN Model
## 1 Introduction
However, changes in the human body due to respiration may not necessarily be observable with contact methods. The movement of the human body due to respiration can be detected by observing the amount of change in the pixels of a video based on optical analysis of motion using motion detection technology, such as optical flow and object detection, performed by applying technology such as frequency analysis based on radar. Changes in temperature due to respiration can also be measured and can be observed by quantitatively measuring changes in temperature in images taken using a thermal imaging camera. In addition, respiration can also be measured based on optical pulse waves through the change in blood flow caused by the change in chest pressure due to respiration [30]. These noncontact methods can overcome some limitations on patients' freedom and enable respiration to be measured more conveniently than with contact methods. Thermal imaging cameras and radar-based methods also involve significant limitations owing to the necessity of using expensive and bulky equipment. However, vision-based technologies using standard, commonly available RGB cameras, such as smartphones and laptops, can also overcome these limitations. Therefore, in this study, we limit the scope of our investigation to remote measurements of respiration using RGB cameras only. Compared with contact respiration measurement methods, noncontact measurements involve several important advantages. First, owing to the noncontact measurement environment, the existing problems of limited freedom of movement or discomfort can be solved. This provides a more relaxed measurement environment and prevents the occurrence of unnatural breathing patterns by minimizing patients' discomfort. Second, there is no need for specialized equipment to measure respiration only. Existing devices for contact respiration measurement are designed for respiration measurement; therefore, they are not used routinely and are difficult to utilize for other purposes. In contrast, the RGB camera-based respiration measurement method uses technology that is commonly encountered daily and can be used for various purposes; this can improve accessibility because of the specificity of the device. Third, a cumbersome preparation process for measurement is not required. For the contact respiration measurement methods, a process must be performed to prepare to attach the sensor to the body for measurement, and some basic knowledge is required to attach the sensor correctly. Because the camera-based noncontact respiration measurement device does not require a separate sensor attachment, the preparation process for the measurement can be greatly simplified. Finally, it can be used as an alternative to contact sensors for patients with skin diseases, children, people with difficulty communicating, and patients with immune disorders who may encounter difficulty attaching sensors to their body. Existing noncontact respiration measurement methods perform image capture in highly controlled situations to achieve sufficient performance, which enables stable measurement of respiration without major impacts on region of interest (RoI) detection performance or signal quality degradation due to noise in the detected RoIs. However, these methods have the disadvantages of being semi-automated and require an environment in which patients' motion is restricted. It is natural for various noise elements to occur in an uncontrolled environment, and thus these methods should be adapted to be used without any additional restrictions to allow stable respiration measurement from the images of the environment that contain noise elements. Therefore, in this study, we propose an RGB camera-based noncontact respiration measurement method that satisfies the following conditions to mitigate the limitations of existing methods and to apply noncontact respiration measurement universally. 1. Noncontact methods can be used to measure respiration without any attached device. 2.