Infrared light, is the night vision monitoring infrared light short name, is to cooperate with the surveillance camera, at night to collect images of light filling equipment. Infrared light emitted by the wavelength of 850nm and 940nm2, are invisible light, with hidden, energy-saving features, nearly 10 years in the field of security monitoring has been widely used.
Infrared light from the material can be divided into:
1, LED light-emitting diode: the most widely used, cost-effective, monitoring distance of 150 meters within the effect is better.
2, laser infrared light: the farthest distance, you can reach more than 200-2000 meters, but the light angle is small.
Infrared light principle
(A) infrared light-emitting diode (LED) principle Infrared light is composed of infrared light-emitting diode (LED) matrix. Infrared light emitting diodes from the infrared radiation efficiency of the material made of PN junction, plus forward bias to the PN junction injection current excitation infrared light. Spectral power distribution for the central wavelength of 830 - 950nm, half - peak bandwidth of about 40nm, as shown in Figure 1 (850nm, 940nm infrared light emitting diode spectrum diagram) shown. It is narrow band distribution, for the ordinary CCD black and white camera can feel the range. Its biggest advantage is that there can be no red storm (using 940 ~ 950nm wavelength infrared tube) or only weak red storm (using 850nm wavelength infrared tube); also has a long life characteristics.
(B) light control soft-switching circuit circuit The infrared light using a light-controlled soft-switching circuit to reduce the impact of its working state transition to extend the life of infrared light
(3) constant current constant current circuit to compensate for infrared light and winter infrared radiation power difference, the infrared light using a constant current regulator circuit, the infrared light-emitting diode optical power stability, thereby enhancing the use of infrared light effect, Extended service life.
(D) the choice of infrared light and the choice of the use of infrared light The most important issue is the infrared light and the camera, lens, protective cover, power supply, such as complete sets of. Some people buy surveillance cameras, lenses, hoods, power supplies, and even after installation to consider buying infrared lights, which is not correct, should be in the design of all the equipment when considering it as an infrared low light Night vision monitoring system engineering to carry out the design.
Infrared light conversion power is fixed, if you want to light angle, it will naturally sacrifice the distance, on the contrary, if the distance will ensure that the sacrifice angle! The choice of infrared light angle is a very important issue. The use of large angle infrared light with a small angle of the lens, there is a waste of light phenomenon. For example, an infrared light, light angle is 80 degrees, (equivalent to F3.5mm lens angle), if with the F35mm lens, then, there will be ninety-nine percent of the light in the lens field of view, but also That is, only one percent of the light is useful, the other is wasted. The use of small angle infrared light with large angle lens, the lamp angle is small, will appear in the image center of a spot, the surrounding relative brightness is low, which is usually said "flashlight" effect.
Under normal circumstances, the angle of the infrared light and the lens of the same angle, is the most scientific match. In addition, the infrared lamp is not the greater the angle, the better the screen effect. Some environments, infrared light angle is too large, but also affect the imaging, such as the corridor, because of its "narrow" features, if the infrared light angle, near the edge of the image is too bright, the formation of "light curtain" phenomenon distant center but not see , Only a white phenomenon. Therefore, the most appropriate approach is the corridor of the infrared light should be slightly narrower than the angle of the lens Second, you can use the "double lamp complementary" technology, wide angle and narrow angle infrared light with, adjust the position, you can achieve the angle and distance complementary effect.
In general, different focal lengths of the lens selection to adapt to the angle of the infrared light, infrared light angle under what conditions should not be greater than the angle of the lens, narrow environment should use a smaller angle than the lens infrared light. Narrow-angle infrared light through the match, you can get the ideal wide-angle effect, better results, lower cost.