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Security infrared camera application principle
Infrared cameras have become a dominant force in night-vision surveillance since their introduction, thanks to their ability to see in the dark, remain discreet, and deliver reliable performance. Their popularity continues to grow as they offer a practical solution for security and monitoring in low-light or no-light conditions.
Before diving deeper into infrared cameras, it’s important to understand some basic concepts about light. Visible light ranges from 0.4 to 0.7 micrometers in wavelength, which is what our eyes can perceive. Beyond that, from 0.7 to 400 micrometers, lies the infrared spectrum—light that is invisible to the human eye. All objects above absolute zero emit thermal radiation in the form of infrared light. For instance, the human body emits more infrared radiation than inanimate objects like buildings, trees, or rocks.
At the heart of every camera is the sensor—commonly known as a CCD or CMOS chip. This semiconductor device converts optical images into digital signals. Unlike the human eye, which cannot detect infrared light, camera sensors are sensitive to a broader range of wavelengths, including infrared. The sensitivity of the sensor, often referred to as the minimum illumination value, determines how well it can capture images in low-light conditions. The higher the sensitivity, the better the camera performs in darkness, especially when it comes to detecting infrared light.
Because of this sensitivity, regular cameras use an infrared cut filter on the sensor to block out infrared light during the day, preventing color distortion in images. However, if an infrared camera also uses such a filter, it would block the very infrared light it relies on at night, making the infrared lamps ineffective. To solve this issue, many high-end infrared cameras are equipped with a dual-filter system. During the day, the filter blocks infrared light to maintain accurate color reproduction. At night, the filter is removed or bypassed, allowing the camera to capture the infrared light emitted by the environment or by built-in infrared LEDs, enabling clear imaging in complete darkness.
This combination of sensor sensitivity and intelligent filtering makes infrared cameras ideal for nighttime surveillance. They don’t rely on visible light but instead use the natural infrared radiation from objects or artificial infrared sources to produce clear, usable images when the human eye cannot see. Whether it's for security, wildlife observation, or industrial applications, infrared cameras provide a powerful tool for seeing beyond the limits of human vision.