Today, the security awareness of consumers in all walks of life has increased, and China's security industry has ushered in new developments. For security monitoring, only real-time monitoring during the day can no longer meet people's needs, and the all-weather seamless security monitoring system has been favored by more engineers and customers.
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Five types of infrared cameras
After infrared technology was discovered by British astronomer Herschel in 1800, more and more scientists are studying how to apply it in various occasions. The application of active infrared camera technology in security monitoring has been fast for nearly two decades. The development technology is relatively mature. While the infrared camera has grown stronger and faster, the product types are constantly diversifying and the application fields are further expanding. There are several types that can be summarized:
First, the halogen camera that has been eliminated: The halogen lamp has a very strong luminous power. Of course, the power consumption and heat generation are relatively large, and the cost is relatively high. Its fatal disadvantage is that it is bulky, has insufficient heat dissipation, and has a very short life. It is generally within a thousand hours, and the red storm phenomenon is particularly serious, so it is not suitable for civil night vision monitoring. Due to the high power and the light-to-heat conversion of the filter, the halogen infrared camera has a particularly hot heating problem, high maintenance cost and short life.
Second, LED infrared camera: LED infrared light is composed of a certain number of infrared light-emitting diodes. The infrared emitting diode is made of a material with high infrared radiation efficiency (commonly used GaAs GaAs), and a forward bias voltage is applied to the PN junction to inject infrared light. The spectral power distribution is center wavelength 830~950nm, half-peak bandwidth. About 40nm, it is a narrow band distribution that is sensible for CCD cameras. LED infrared camera is generally suitable for short distances of 10~100 meters, and has the highest market share, but there are problems of uneven illumination. It is mainly suitable for short distances such as corridors, halls, warehouses, etc., indoor and building peripherals, community perimeters, roads, etc. monitor.
Third, the LED array infrared camera: the core of the array type infrared lamp is an LED array, which has the following advantages compared with the conventional LED: 1. The brightness is high, the output of the single LED array is about 1W~30W, and the brightness is about It is the output of conventional single LED 5~15mW, so the range is far; 2, the electro-optical conversion efficiency is high, the electro-optical conversion efficiency of ordinary infrared LED is only about 10%, and the LEDArray electro-optical conversion efficiency is improved to 25%. 3, small size, LEDArray technology will be highly integrated in the lighting unit, much smaller than the ordinary LED infrared lamp product under the same brightness index; 4, long life, LEDArray life is 50,000h, much higher than ordinary LED life . The array type infrared lamp product has an obvious deficiency, that is, "eccentricity phenomenon". Since the illumination angle can reach 120-180 degrees, it is necessary to reduce the light supply angle through the lens to match the camera lens, so that inevitably a lot of light deviates from the center of the lens, resulting in poor light transmission efficiency. The LED array infrared camera is basically the same as the LED infrared camera. It is more suitable for medium and short-distance monitoring applications such as halls, warehouses, etc., indoor and building peripherals, community perimeters, and roads.
Fourth, the dot matrix infrared camera uses a dot matrix infrared light source. The third-generation infrared illuminating components used in dot matrix infrared lamps are based on the second generation of array-based infrared lamps (LED--Array), so it is also called the second-generation LED-Array. Compared with the first generation, the second-generation LED-Array has the advantages of small size, good heat dissipation, slow decay, long life and a rated life of 50,000 hours. Dot matrix infrared lamps are also called high-power array infrared. The biggest difference from low-power array infrared is higher brightness and lower cost. Through independent lenses, the angle of light distribution can be adjusted according to the needs of use. The first generation of "flashlight effect" problem and the second generation of "eccentricity phenomenon".
Fifth, laser infrared camera: laser infrared camera illumination distance is generally up to 300~5000 meters. Due to energy concentration, the angle is small and close, and the cost is still high. It is more suitable for monitoring in forest fire prevention, oil field, railway, water conservancy, scenic area, military, aquaculture, port and Ping An market. With the further reduction of cost, it has been applied to many areas requiring night vision monitoring including community. . Therefore, the infrared camera needs to determine the camera type according to the specific use environment, especially the night environment.
Infrared camera common technical debugging
First, the installation notes
1. Debugging the infrared light must be done at night. The infrared beam illumination position is adjusted at night by a rendering device such as a monitor. And can effectively adjust the lens aperture settings.
2. The infrared light can't directly face the camera. The infrared light seen by the camera is like the sunlight seen by humans, which will make the image appear white.
3. The infrared lamp is not necessarily installed in the same position as the camera. If the camera is far away from the object to be illuminated, consider installing the infrared lamp between the two. The best way to install in the same position is to overlap the camera with the infrared light and the camera.
4. The installation height of the infrared lamp should not exceed 4 meters. Too high will affect the reflectivity of light. The angle should be 20 degrees from the top to the bottom, and the reflectance should be too large.
5. The working index of the infrared lamp must be guaranteed (see the product manual for details). For example, the power supply of the infrared lamp must be higher than the operating power of the infrared lamp itself.
6. Users should first read the instruction manual carefully when using the infrared light, especially the precautions for ensuring the safety of personal equipment. Check whether the matching aspects described above meet the requirements, and whether the influencing factors should be taken into consideration, if the requirements are not met, the equipment used can be adjusted in time.
Second, the precautions when using
Angle problem: First of all, the use of large-angle infrared light with a small angle of the lens, there is a waste of light. Secondly, not the larger the angle of the infrared light, the better the picture.
The problem of the amount of light passing through: the relative aperture determines the light-passing ability of the lens, and the amount of light passing through the lens with a relative aperture of f1.0 is four times that of the lens with a relative aperture of f2.0. The same camera and infrared light are matched with the above two types. The lens and infrared distance can be doubled. The large-aperture lens is four to ten times better than the conventional lens in infrared monitoring. It is reasonable to say that it should be an essential accessory for infrared night vision monitoring. However, due to the high cost and technical difficulty, Most infrared product manufacturers do not have the ability to supply.
The problem of focus shift: visible light and infrared light are different in wavelength, the imaging focus is not on a plane, resulting in clear image under visible light conditions in the daytime, blurred under nighttime infrared light conditions, or clear image under nighttime infrared light conditions, daytime visible light conditions The image is blurred. It can be solved in three ways. First, using an autofocus integrated camera; second, using a dedicated focus without offset lens; third, using a professional adjustment tool, can also be achieved under existing lens conditions. No offset
Color problem: All black and white cameras are infrared light. Infrared light is a kind of stray light for color cameras under visible light conditions, which will reduce the sharpness and color reproduction of color cameras. The color camera filters are blocked. Infrared is involved in imaging. In order to make the color camera sense infrared, there are two ways to do this. First, switch the filter to block the infrared light from entering under visible light conditions; remove the filter in the absence of visible light and let the infrared light enter. The image obtained by the scheme is of good quality, but the cost is high and the switching mechanism causes a certain failure rate. Second, a specific infrared channel is opened on the filter, allowing infrared light of the same wavelength as the infrared light to come in. The method does not increase the cost, but the color reproduction is slightly worse.
How far can infrared night vision be? If the technology is at home, the infrared night vision system of 100 meters or more is not difficult. The technology is home, which means that you must be proficient in infrared light technology, infrared camera technology and infrared sensor lens technology. The three are indispensable. Now the products on the market have been more than 500 meters away, but the cost is relatively high, and the civilian market is still relatively limited.
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