British astronomer Herschel discovered infrared technology in 1800. In the constant efforts of the scientific community, infrared technology has also been applied to various occasions. The most typical one for security applications is the infrared camera.
Infrared cameras can be divided into 2 categories, analog infrared cameras and infrared network cameras. But they all have the same characteristics, which are mainly manifested in the different characteristics of infrared light source and the choice of low illumination camera. Only by combining these two points with an infrared camera can you become an excellent product.
In selecting different infrared light sources and distances, the main infrared light source characteristics for different applications are as follows: Infrared light is an invisible light with a wavelength greater than 780 nm. Generally, the infrared lamps of current infrared cameras have the following types. 1. Use infrared light emitting diode LEDs or LED arrays to generate infrared light. Such devices generate infrared light by recombining electrons and holes in a gallium arsenide (GaAs) semiconductor. 2. The infrared laser diode LD can also be used as an infrared light source. However, it is necessary to excite or pump electrons in a lower energy state to a higher energy state, and maintain the stimulated radiation infrared light by reversing a large amount of particle distribution and resonating.
The first is an infrared lamp composed of a semiconductor gallium arsenide LED array, especially an array-type integrated light-emitting chip LEDArray that is now developed using a new technology. Its LED-Array has an optical output of 800mw-1000mw, which has become a replacement for ordinary LEDs. The LED-Array has a half-power angle of 10-120° (variable angle). Since the LED-Array is a highly integrated LED and the size is only one penny coin, its life span is 50,000 hours.
The second is to use an infrared laser diode LD. For the monitoring of ultra-long-distance scenes of more than 1km, it is still necessary to select an infrared LD source. Because semiconductor lasers have higher brightness and better directivity than LEDs.
Infrared camera installation and debugging need to pay attention to the following issues:
First of all, debugging infrared lights 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.
Secondly, 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.
Again, the infrared light is not necessarily mounted in the same position as the camera. If the camera is far away from the object being illuminated, consider installing the infrared light between the two. The best way to install in the same position is to overlap the camera with the infrared light and the camera.
Finally, 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.
The use of large-angle infrared light with a small angle of view lens, there is a waste of light. Secondly, the larger the emission angle of the infrared light, the better the picture effect. The relative aperture determines the light-passing ability of the lens. The relative light-through of 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 lenses, and the infrared distance is It 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 products 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 below is blurred. 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 prevent infrared rays from participating in imaging. There are two ways to make the color camera sense infrared. 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 quality is good, but the cost is high and the switching mechanism will cause a certain failure rate. Second, open a specific infrared channel on the filter, allowing infrared light of the same wavelength as the infrared light to come in. This method does not increase. Cost, but the color reproduction is slightly worse.
At present, infrared night vision distance has been more than 500 meters, and price is also one of the reasons. Among them, infrared light, infrared camera technology, infrared lens is the core.
