When security requirements evolve from passive detection to active defense, various image processing algorithms relying on intelligent analysis become important. Among them, fog-through processing integrates multiple image algorithms and is an important class of image processing technology. The known fogging algorithms can be roughly divided into two categories: one is a non-model image enhancement method, which enhances the contrast of the image and satisfies the requirements of subjective vision to achieve the purpose of clarity; the other is a model-based image. The restoration method, which examines the causes of image degradation, models the degradation process, and uses reverse processing to ultimately solve the problem of image restoration.
In order to obtain better processing results, the camera manufacturers will add a special image processing chip, which can automatically detect the density of the image and keep the details of the image signal to the utmost, achieving color enhancement, contrast enhancement, edge enhancement, contrast enhancement and brightness enhancement. , And the density division, deblurring and other operations, so that the video quality under different scenes has been significantly improved to achieve the purpose of fog. According to the manufacturer's capabilities and R&D choices, they will choose to perform corresponding processing on different chips such as DSPs or FPGAs.
The chip will read the video stream information in real time and determine whether the fog-through mode needs to be enabled by comparing the parameters. That is, the fog can be automatically detected. The fog can be determined by the preset mode and the fog mode can be selected. .
Second, optical fog technology
Natural light is composed of light waves with different wavelengths. The visible range of the human eye is approximately 390-780 nm. Wavelengths from long to short correspond to seven colors of red orange, blue-green, green-orange violet, respectively. Among them, the wavelength less than 390 nm is called ultraviolet light, and the wavelength is greater than 780 nm. It's called infrared. Different wavelengths of light have different characteristics because of different wavelengths, and fog and dust affect the cause of visible light imaging. Infrared rays, because they have longer wavelengths, are less affected by aerosol during propagation, and can penetrate certain concentrations of haze and dust. To achieve accurate focus, this is the basis for optical fogging.
(I) The principle of the lens is that the focus of optical fogging is the interception and accurate focusing of light in a specific near-infrared band, and most of this work is done by the lens. It can be said that the quality of the lens determines the effect of optical fogging. The difficulty of the lens design lies in the optical design, including the grasp of the optical path and the selection of the filter. Secondly, the selection of materials and technology also determine the effect of the finished product. The biggest difference of the fog lens is that it can bear the width of the infrared band, that is, the latitude of the focal plane. In principle, the wider the available near-infrared wavelength band, the better, but it is limited by the difficulty of designing the optical path of the lens and the CCD's photosensitivity. Currently, the longest infrared band available in the security industry is known to be 1100 nm.
(II) Filters People who understand the day-to-night conversion cameras are familiar with the filters. Generally, this type of camera is equipped with two filters. One is responsible for filtering the light waves outside the visible light during the day to make the image clearer and brighter. Applied at night, it is responsible for the release of the infrared band that the CCD can carry, enabling infrared monitoring at night.
The professional fog lens incorporates highly targeted filters. The function is to precisely intercept the light in the desired wavelength band. In order to adapt to specific environmental conditions, multiple filters for different bands are often loaded and linked to the camera via the 485 interface. To achieve switching. Normally, a camera with a fog lens can only have the day and night conversion function in the basic imaging performance. However, considering the high cost of the fog lens, some camera manufacturers are also looking for a more economical optical fogging mode. In the past two day-night conversion cameras, we innovatively added four filters inside the camera. In addition to achieving day and night conversion, we also achieved a strong light suppression by adding a filter that selectively filters 400-nm to 400-nm wavelength light. Of course, in order to more accurately capture the near-infrared band suitable for imaging, a fog filter is also particularly added to achieve a more economical optical fogging. This mechanical device can be automatically controlled by the camera or manually switched. The combination of optical penetrating fog and electro-permeating fog is a four-filter color photoelectric combined with intelligent fogging camera, which can achieve twice the visibility of fog.
Third, the development of two kinds of technology analysis (A) bottleneck and development of optical fog technology because of the direct use of light through the haze of the near-infrared wave band imaging, optical fog can only get a black and white surveillance picture, but its imaging effect is outstanding It has also been used in maritime affairs and oceans. On the other hand, due to the high cost of the lens, although the Ping An City and other large-scale projects and even the civilian market have seen certain fog demand in recent years, the actual number is still limited.
At the same time, because the technology is relatively mature, relying on the lens or optics to achieve better fogging requires an alternative approach. In the short term, the latitude of the lens to the wavelength is difficult to extend beyond 1100 nm, but if you do not take into account the visible light, you can also achieve a certain extension in the near-infrared band; so you can consider loading two sets of lenses in a device, under normal circumstances The visible light lens and the foggy day use a special fog lens, which not only preserves the visible color picture, but also makes the tolerance of the fog lens more comfortable and enables multi-image contrast monitoring.
(B) The emergence of an integrated movement to help electronic fog through the diversification of products, the market has continued to mature, the emergence of integrated fog machine core for the popularity of fog products can be significant. In recent years, all-in-one cameras released use pure electronic fogging, and are processed by an embedded FPGA chip. It can output color images. This algorithm can distinguish factors such as distant and distant fog in the distant view. It can enhance each pixel to achieve the best effect in the area, which is different from the overall improvement of the contrast ratio in the past without delay. Moreover, high-speed operation of the chip will produce noise points, and the effect will be more prominent when the nighttime illumination is insufficient. The integrated fog lens core commonly uses CCD sensors and large aperture lenses to achieve a good low-light effect. On the other hand, it is easier to achieve high-definition fog.
In the past, the demand for fog penetration was basically in the bolt, but the monitoring distance of the bolt was generally short, and if the fog was not dense within a short distance, the picture would not have much impact. The all-in-one monitor has a larger range and the zoom is optional, so the haze has a greater impact on it. The appearance of the one-piece fog penetrer is to achieve the penetration of fog within a larger monitoring distance, and as the product is finished, the integrated fogging machine core will reduce the investment of the fogging equipment and realize a greater application.
Future trends
In practical applications, electron fogging, as an ISP image restoration technique, has a fatal flaw in that it cannot restore lost information when the fog is severe. This is determined by its imaging principle. Even if the image restoration algorithm is advanced, it cannot be improved. Once the concentration of haze in the environment changes, the effect of electron fogging will not be controllable. That is to say, the environment adaptability of electronic fogging is weak, and the cost-effectiveness of developing more advanced image restoration algorithms is not high. Therefore, I believe that electronic monitoring based on monitoring needs The fogging technology will gradually converge.
Optical fogging has long been used in forest fire prevention, maritime affairs, and border defense. It has a long history of practical application, and its effect has been recognized by users, but it is limited by high costs and cannot be widely promoted in other general industries. With the emergence of new technologies, the cost issue has been resolved, and it is believed that its application prospects in various industries will increase.
In addition to improving the optical fogging effect, in addition to the camera's own image processing capabilities, lens, window and other supporting imaging systems should also have a higher transmittance of infrared light, so the perfection of the supporting system and even further upgrade of the sensor is optical fogging. The direction of future efforts.
In order to obtain better processing results, the camera manufacturers will add a special image processing chip, which can automatically detect the density of the image and keep the details of the image signal to the utmost, achieving color enhancement, contrast enhancement, edge enhancement, contrast enhancement and brightness enhancement. , And the density division, deblurring and other operations, so that the video quality under different scenes has been significantly improved to achieve the purpose of fog. According to the manufacturer's capabilities and R&D choices, they will choose to perform corresponding processing on different chips such as DSPs or FPGAs.
The chip will read the video stream information in real time and determine whether the fog-through mode needs to be enabled by comparing the parameters. That is, the fog can be automatically detected. The fog can be determined by the preset mode and the fog mode can be selected. .
Second, optical fog technology
Natural light is composed of light waves with different wavelengths. The visible range of the human eye is approximately 390-780 nm. Wavelengths from long to short correspond to seven colors of red orange, blue-green, green-orange violet, respectively. Among them, the wavelength less than 390 nm is called ultraviolet light, and the wavelength is greater than 780 nm. It's called infrared. Different wavelengths of light have different characteristics because of different wavelengths, and fog and dust affect the cause of visible light imaging. Infrared rays, because they have longer wavelengths, are less affected by aerosol during propagation, and can penetrate certain concentrations of haze and dust. To achieve accurate focus, this is the basis for optical fogging.
(I) The principle of the lens is that the focus of optical fogging is the interception and accurate focusing of light in a specific near-infrared band, and most of this work is done by the lens. It can be said that the quality of the lens determines the effect of optical fogging. The difficulty of the lens design lies in the optical design, including the grasp of the optical path and the selection of the filter. Secondly, the selection of materials and technology also determine the effect of the finished product. The biggest difference of the fog lens is that it can bear the width of the infrared band, that is, the latitude of the focal plane. In principle, the wider the available near-infrared wavelength band, the better, but it is limited by the difficulty of designing the optical path of the lens and the CCD's photosensitivity. Currently, the longest infrared band available in the security industry is known to be 1100 nm.
(II) Filters People who understand the day-to-night conversion cameras are familiar with the filters. Generally, this type of camera is equipped with two filters. One is responsible for filtering the light waves outside the visible light during the day to make the image clearer and brighter. Applied at night, it is responsible for the release of the infrared band that the CCD can carry, enabling infrared monitoring at night.
The professional fog lens incorporates highly targeted filters. The function is to precisely intercept the light in the desired wavelength band. In order to adapt to specific environmental conditions, multiple filters for different bands are often loaded and linked to the camera via the 485 interface. To achieve switching. Normally, a camera with a fog lens can only have the day and night conversion function in the basic imaging performance. However, considering the high cost of the fog lens, some camera manufacturers are also looking for a more economical optical fogging mode. In the past two day-night conversion cameras, we innovatively added four filters inside the camera. In addition to achieving day and night conversion, we also achieved a strong light suppression by adding a filter that selectively filters 400-nm to 400-nm wavelength light. Of course, in order to more accurately capture the near-infrared band suitable for imaging, a fog filter is also particularly added to achieve a more economical optical fogging. This mechanical device can be automatically controlled by the camera or manually switched. The combination of optical penetrating fog and electro-permeating fog is a four-filter color photoelectric combined with intelligent fogging camera, which can achieve twice the visibility of fog.
Third, the development of two kinds of technology analysis (A) bottleneck and development of optical fog technology because of the direct use of light through the haze of the near-infrared wave band imaging, optical fog can only get a black and white surveillance picture, but its imaging effect is outstanding It has also been used in maritime affairs and oceans. On the other hand, due to the high cost of the lens, although the Ping An City and other large-scale projects and even the civilian market have seen certain fog demand in recent years, the actual number is still limited.
At the same time, because the technology is relatively mature, relying on the lens or optics to achieve better fogging requires an alternative approach. In the short term, the latitude of the lens to the wavelength is difficult to extend beyond 1100 nm, but if you do not take into account the visible light, you can also achieve a certain extension in the near-infrared band; so you can consider loading two sets of lenses in a device, under normal circumstances The visible light lens and the foggy day use a special fog lens, which not only preserves the visible color picture, but also makes the tolerance of the fog lens more comfortable and enables multi-image contrast monitoring.
(B) The emergence of an integrated movement to help electronic fog through the diversification of products, the market has continued to mature, the emergence of integrated fog machine core for the popularity of fog products can be significant. In recent years, all-in-one cameras released use pure electronic fogging, and are processed by an embedded FPGA chip. It can output color images. This algorithm can distinguish factors such as distant and distant fog in the distant view. It can enhance each pixel to achieve the best effect in the area, which is different from the overall improvement of the contrast ratio in the past without delay. Moreover, high-speed operation of the chip will produce noise points, and the effect will be more prominent when the nighttime illumination is insufficient. The integrated fog lens core commonly uses CCD sensors and large aperture lenses to achieve a good low-light effect. On the other hand, it is easier to achieve high-definition fog.
In the past, the demand for fog penetration was basically in the bolt, but the monitoring distance of the bolt was generally short, and if the fog was not dense within a short distance, the picture would not have much impact. The all-in-one monitor has a larger range and the zoom is optional, so the haze has a greater impact on it. The appearance of the one-piece fog penetrer is to achieve the penetration of fog within a larger monitoring distance, and as the product is finished, the integrated fogging machine core will reduce the investment of the fogging equipment and realize a greater application.
Future trends
In practical applications, electron fogging, as an ISP image restoration technique, has a fatal flaw in that it cannot restore lost information when the fog is severe. This is determined by its imaging principle. Even if the image restoration algorithm is advanced, it cannot be improved. Once the concentration of haze in the environment changes, the effect of electron fogging will not be controllable. That is to say, the environment adaptability of electronic fogging is weak, and the cost-effectiveness of developing more advanced image restoration algorithms is not high. Therefore, I believe that electronic monitoring based on monitoring needs The fogging technology will gradually converge.
Optical fogging has long been used in forest fire prevention, maritime affairs, and border defense. It has a long history of practical application, and its effect has been recognized by users, but it is limited by high costs and cannot be widely promoted in other general industries. With the emergence of new technologies, the cost issue has been resolved, and it is believed that its application prospects in various industries will increase.
In addition to improving the optical fogging effect, in addition to the camera's own image processing capabilities, lens, window and other supporting imaging systems should also have a higher transmittance of infrared light, so the perfection of the supporting system and even further upgrade of the sensor is optical fogging. The direction of future efforts.
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