Analysis of the application of LED infrared light source in surveillance cameras

With the increasing demand for night vision monitoring in security video surveillance system projects, infrared cameras with LED light sources have entered the mainstream camera market, and sales are increasing day by day. This article discusses the application of LED infrared light sources in camera night vision technology.

　　Selection of LED infrared light source

　　The infrared light projection of the infrared surveillance camera is like a flashlight. When the projection angle is small, the projection distance is farther, but the monitoring range will be smaller. The opposite is true. At present, the better quality infrared surveillance cameras in China generally use LED infrared light modules produced and packaged by Taiwanese manufacturers, such as Dingyuan, Hongbai, Lite-On, etc. In the minds of most users, they think that the number of LED infrared lights determines the quality of infrared surveillance cameras, but in fact, this view is not very accurate. At present, the LED infrared lights of infrared surveillance cameras on the market are generally designed in two ways: external or built-in. Their size and power will affect the detection distance of the camera. For example, the space for built-in LED lights is small, so the monitoring distance is also shorter. Industry insiders pointed out that in fact, the power of infrared LED lights is the key to directly affecting the irradiation distance of infrared surveillance cameras.

　　At the same time, in order to achieve the best effect, the design of LED light components and the matching between LED lights and lenses are also very important. To improve the actual function of infrared surveillance cameras, first of all, we must carefully select LED infrared lights. Only high power and low current will not cause LED overheating; secondly, we must choose aluminum substrates with better heat dissipation to avoid problems such as poor waterproofing, fogging and dust caused by adding fans to general fiberglass substrates for heat dissipation; thirdly, to prevent the exposure problem of infrared surveillance cameras, we must fundamentally solve the reflection of LED infrared lights. Metal partitions can be installed between LED lights and lenses to isolate them to prevent interference from LED lights; in addition, in order to prevent fogging, the waterproofing of infrared surveillance cameras must also be strengthened; the last is the focus problem. Usually, infrared surveillance cameras focus normally during the day, but often cannot focus normally at night. This must depend on the technical improvement of the ED glass inside the lens.

　　How to reduce the attenuation of infrared lamps as much as possible and extend the service life of infrared monitoring products is also an important topic. In the interview, Hu Ping of Hikvision said that this goal can be achieved through the following methods: select high-quality infrared lamps; use metal film reflective technology; use high-efficiency optical lenses (5% higher light transmittance than ordinary glass); maintain constant current and constant voltage circuit design to ensure that the light source works in a stable current state; use LED circuit protection system; each group of infrared lamps is powered separately to avoid vicious current circulation, even if a single lamp is damaged, it will not cause the failure of all lamps; multiple designs can also be used to ensure the life of a single infrared lamp, etc.

　　Application Analysis of LED Infrared Light Source

　　The infrared LED used in the remote control does not emit completely infrared light, but also contains some visible light (red) components, so the naked eye can see a little light. The LED used in the remote control generally has an emission angle of about 30 degrees, so the user can operate effectively even if they do not completely aim at the target.

　　When there is no external infrared interference, the remote control distance can reach 5 meters or more. However, due to the presence of infrared in natural light, the actual distance is generally within 3 meters. Of course, increasing the transmission power of the remote control can increase the remote control distance. In theory, a 100% increase in transmission power will increase the remote control distance by 40%.

　　Surveillance cameras also use infrared LEDs. I personally think that most of them use products similar to remote controls. The camera's sensitive range includes the infrared region, so using infrared LED lighting can allow the camera to obtain clear images. The effective distance of a single LED lighting is generally no more than 2 meters, and at this distance, the brightness is already very low. Therefore, common surveillance uses multiple LEDs side by side. The more LEDs there are, the longer the effective range is, and it also follows the approximate relationship of 100%-40%.