Can human infrared sensors penetrate glass? Why

A human infrared sensor is a sensor that uses the principle of infrared radiation to detect the presence or absence of a human body. It detects the human body by detecting the infrared radiation emitted by the human body. However, human infrared sensors cannot penetrate glass for the following reasons:
The wavelength range of infrared radiation: The human infrared sensor mainly detects the infrared radiation emitted by the human body, with a wavelength range between 8-14 microns. The absorption and reflection characteristics of glass for infrared radiation will change with wavelength. For infrared radiation in the range of 8-14 microns, the transmittance of glass is low, so human infrared sensors cannot penetrate glass.
Optical properties of glass: Glass is a transparent solid material, and its optical properties include refractive index, reflectivity, and absorptivity. For infrared radiation, glass has a higher refractive index and reflectivity, but a lower absorption rate. When infrared radiation encounters glass, most of it will be reflected or refracted, and only a small portion can penetrate the glass. Therefore, human infrared sensors cannot penetrate glass.
The thickness and material of glass: The thickness and material of glass also affect its transmittance to infrared radiation. Generally speaking, the thicker the glass, the stronger its ability to absorb and reflect infrared radiation, and the lower its transmittance. In addition, the transmittance of infrared radiation varies among glass materials. For example, ordinary glass has a lower infrared transmittance, while infrared glass has a higher infrared transmittance. However, even infrared glass has a low transmittance for infrared radiation in the range of 8-14 microns, which cannot meet the detection requirements of human infrared sensors.
Environmental factors: In addition to the characteristics of glass itself, environmental factors can also affect the detection performance of human infrared sensors. For example, when there are pollutants such as dirt and water droplets on the surface of glass, it will further reduce the transmittance of the glass to infrared radiation. In addition, factors such as environmental temperature and humidity can also affect the propagation of infrared radiation, thereby affecting the detection performance of human infrared sensors.
The working principle of human infrared sensors: The working principle of human infrared sensors is to detect the infrared radiation emitted by the human body to achieve detection of the human body. When there are obstacles such as glass between the human infrared sensor and the human body, infrared radiation cannot directly reach the sensor, so the sensor cannot detect the presence of the human body. In addition, the detection range and sensitivity of human infrared sensors are also affected by obstacles such as glass, resulting in a decrease in detection effectiveness.
Application scenarios of human infrared sensors: Human infrared sensors are mainly used in smart homes, security monitoring, medical and health fields. In these application scenarios, human infrared sensors usually need to directly detect the presence of the human body and cannot be interfered by obstacles such as glass. Therefore, the inability of human infrared sensors to penetrate glass limits their application range to a certain extent.
Alternative solution: Although human infrared sensors cannot penetrate glass, there are also some alternative solutions on the market that can achieve similar functions. For example, other types of sensors such as ultrasonic sensors and microwave sensors can be used to detect the presence of the human body. These sensors are not affected by obstacles such as glass and can achieve a wider range of applications.
In summary, human infrared sensors cannot penetrate glass mainly due to factors such as the absorption and reflection characteristics of glass towards infrared radiation, the optical properties of glass, environmental factors, and the working principle of human infrared sensors. Although human infrared sensors are limited in certain application scenarios, there are still other types of sensors on the market that can replace their functions.