IR Camera Frequently Asked Questions

common problem

First, the image color cast problem

All black and white cameras are infrared light sensitive. Under visible light conditions, infrared light is a stray light for color cameras, which reduces the clarity and color reproduction of color cameras. The camera uses a CCD to sense all light (visible light, infrared, ultraviolet, etc.). This causes the image taken during the day to be different from the image produced by our eyes only visible light. Because the CCD senses infrared light, it will interfere Operation to the DSP leads to color cast. A lot of technical research and development have been carried out to address the problem of color cast of infrared camera surveillance images. At present, there are mainly three ways to solve this problem. The first is to debug the RGB hue on the CCD for DSP processing. This approach does not cure the symptoms, and not every manufacturer has such chip processing capabilities. The second is to switch through filters, using all filters during the day. In addition to the infrared filter, an ordinary quartz plate is used to trim the light at night; the third is to change the model and replace the IRCUT camera with a dual CCD infrared camera. Under the condition that the color is not discolored during the day, an infrared camera can be added. Service life.

Second, the heat dissipation problem

Due to the configuration of the infrared lamp with a large amount of heat, after the infrared lamp is activated, there will be heat concentration in the front of the infrared camera during the entire working period (in 12 hours), that is, the temperature at the front end of the cavity is too high. It will affect the normal operation of other parts such as the camera. For example, if there are 50 ï¿  5 infrared lamp boards, the temperature on the LED board can reach almost 90 degrees if it is operated for a long time.

Because the radiant power of infrared light-emitting LEDs is proportional to the current, many non-standard manufacturers increase the current to increase the irradiation effect. However, the larger the current, the higher the temperature. Although the irradiation effect is improved, the machine itself will be greatly damaged due to the overheating of the LED. Among them, the CCD behind the LED board is the most direct victim. CCD can only support 60-70 degrees.

In order to solve this problem, different manufacturers use different methods. There are roughly the following:

1. Reduce the current. Using an infrared lamp with low power consumption instead of an infrared lamp with large power consumption, although the heat dissipation is reduced, the effect is definitely not as good as the latter when irradiating a long distance.

2. Adding a cooling fan inside the machine is definitely effective, but the test of the fan is very strict, and the addition of a fan is also a test of the design of the casing, and it must be practical to ensure its beauty.

3. Use a constant current power supply. Keep the current constant and control the heat dissipation of the LED.

4. Grouping of LED lights. For example, with 24 infrared rays, you can arrange them into 3 groups to reduce heat.

5. Selection of structural materials. For example, the LED lamp board and the housing are made of a material with good heat dissipation such as aluminum alloy.

6. The automatic cooling and heating air conditioner with forced cooling and cooling effect is used to automatically adjust the internal temperature of the body, which solves this problem well.

Life issues

From the perspective of external red lights, increasing life and distance are often contradictory. Because if the manufacturer needs to increase the distance of the infrared lamp, it is bound to increase the power of the infrared lamp, and increasing the power will definitely shorten the life of the infrared lamp. Some manufacturers deliberately increase the power of the infrared lamp in order to blindly pursue the distance of the infrared lamp. So that the life of the infrared lamp is greatly reduced. And with the increase of power, the internal temperature of the camera increases, making the camera easily damaged, causing a vicious cycle.

In this case, we cannot increase the brightness of the infrared lamp by increasing the supply current to make it work overload. Although the infrared performance is optimized on the surface, the life of the infrared lamp is seriously affected. To improve the life of the infrared lamp, it is necessary to ensure that the infrared lamp is unloaded, and to increase the number of infrared lamps to ensure the effective distance while unloaded; some manufacturers use high-conductivity materials such as aluminum substrates and increase the air-cooled components. Use, increase the area of ​​the shell, etc. to increase the heat dissipation capacity of the fuselage, thereby increasing the life.

In the circuit control part, some manufacturers also adopt pulse width modulation law to keep the current of the infrared lamp constant, thereby reducing the heating of the infrared lamp and achieving the purpose of extending the life. After adopting the pulse width modulation law, no matter how the external input current fluctuates, the current that enters the infrared lamp through the circuit is very stable, thereby ensuring that the infrared lamp can exert its maximum efficiency and prolong its life.

Fourth, the red storm problem

What is a red storm? Let's take a look at this concept first. The red storm is because the infrared rays emitted contain visible light components. Light with a wavelength exceeding 700nm is called infrared. Infrared rays above 900nm are basically no red burst. The shorter the wavelength, the stronger the red burst, and the higher the infrared sensitivity.

Some infrared camera manufacturers have promoted whether it is possible to produce red storm-free infrared lamps as a technical issue. It seems that red storms are low-tech, and red storms are high-tech. In fact, infrared lamps can be completely free of red storms (using infrared tubes with a wavelength of 940 to 950 nm) or only have weak red storms. At present, there are two mainstream infrared lamps on the market, one is slightly red burst, with a wavelength of about 850 nm; the other is red burst, with a wavelength of about 940 nm. With the same camera, the sensitivity at the 850nm wavelength is 10 times better than the sensitivity at the 940nm wavelength. Therefore, the 850nm infrared light with a slight red storm has higher efficiency and should become the first xuan term of infrared cameras.