Light-emitting diodes in television monitoring system

In the television monitoring system project, infrared lamps were rarely used in the past. However, due to the increase in social crime rates, the role of infrared in night surveillance has become more prominent. Not only vaults, oil depots, armory, library of books, cultural relics, prisons It is adopted by other important departments and is also adopted in general monitoring systems. Even the residential area television monitoring project also uses infrared cameras. This shows that people's requirements for television monitoring system engineering become more and more standard and more and more. More and more important sites require 24-hour continuous monitoring.

Infrared lamps are divided into semiconductor solid-emitting (infrared emission diode) infrared lamps and thermal radiation infrared lamps according to their infrared radiation mechanism. Most infrared cameras use LED infrared light-emitting diodes as the main material of infrared cameras. .

Infrared lamps using infrared emitting diodes, the principle and characteristics are as follows: The light emitting diode matrix composed of infrared light. The infrared emitter diode is made of a material with high infrared radiation efficiency (usually gallium arsenide GaAs) made of PN junction, plus a forward bias to inject infrared current into the PN junction to stimulate infrared light. The spectral power distribution is center wavelength of 830-950 nm, and the half-peak bandwidth is about 40 nm. It is a narrow-band distribution, which is a range that a common CCD black-and-white camera can sense. Its greatest advantage is that it can be completely free of red storms (using infrared tubes at 940 to 950 nm wavelengths) or only weak red storms (red storms have visible red light) and long life.

The emission power of infrared light emitting diodes is expressed in terms of irradiance μW/m2. In general, the infrared radiation power is proportional to the forward operating current, but near the maximum rated value of the forward current, the temperature of the device rises due to the heat dissipation of the current, and the optical emission power decreases. Infrared diode current is too small, it will affect the radiated power to play, but the operating current is too large will affect its life, and even make the infrared diode burned. Currently, there is a built-in heat dissipation system inside the camera that can extend the stability of the camera.