Label: Low illumination AGCON This article refers to the address: http:// In the security city of “Safe City†project, finance, cultural, hotel, office, residential, safe village, campus, port, highway, street, etc., the performance requirements of the camera are getting higher and higher, because the conventional camera is difficult Meeting the needs of 24-hour continuous monitoring, the low-light camera immediately became the primary choice for 24-hour surveillance. What is a low illumination camera A low-light camera, as seen from the name, refers to a camera that still has a sharper image in the case of darker lighting (low illumination). In the security industry, it is generally believed that a camera with an illuminance indicator lower than 0.1 Lux (F1.2, AGCON, 30 IRE) can be called a low-light camera. According to the traditional name, low-light cameras can be divided into two categories: "Starlight" and "Moonlight". Roughly speaking, cameras with illumination below 0.01Lux (F1.2, AGCON, 30IRE) are called "Starlight". A low-light camera with a illuminance between 0.1Lux and 0.01Lux (F1.2, AGCON, 30IRE) is called a "moonlight-level low-light camera." Of course, there is no clear definition in the above-mentioned division of the industry, or there may be differences, but it may be a consensus agreed by the industry. The low-light cameras in the industry, in addition to mechanical color-to-black (also known as ICR), now include hemispheres, all-in-ones, domes, and conventional guns. The low illumination index of the camera is a parameter for evaluating the sensitivity of the camera. The smaller the number, the higher the sensitivity of the camera and the better the performance of low illumination. The 0.1Lux (F1.2, AGCON, 30IRE) mentioned above is not only "0.1Lux". "This illuminance indicator, and there are additional restrictions: F1.2, AGCON, 30IRE, why do you have these restrictions? It is to ensure the fairness, consistency and effectiveness of the camera imaging evaluation. F1.2 indicates that when the camera reaches low illumination, it requires the lens flux (F value, luminous flux, measured by the ratio of the focal length f of the lens to the aperture D of the lens. The smaller the F value, the larger the aperture and the luminous flux reaching the CCD. The larger the value, the smaller the F value is, the better the lens is. AGCON indicates the state when the camera's automatic gain is turned on. 30IRE means that the video output of the camera reaches the lowest level of quality on the monitor (standard image is 100 IRE or 700 mV; 210 volts at 30 IRE, the lowest level, lower than 30 IRE is useless image). In addition to the restrictions explicitly written here, in fact, there is an implicit condition, that is, the electronic shutter of the camera is the default 1/50s (in the PAL system), because only under these conditions, the judgment is made. Comparable and fair. Often on some camera specifications, only one "0.0001lux" is seen, the low illumination value is written very low, but there is no additional condition behind, so it is not clear whether the camera is really low illumination. Perhaps it is just a false propaganda. Why do you need a low illumination camera? In the "Safe City" project, finance, cultural, hotel, office, residential, safe village, campus, port, highway, street, etc., the camera performance requirements are relatively high, because the conventional camera is difficult to meet 24-hour continuous monitoring The demand, so low-light cameras become the primary choice. In these applications, such as the “Safe City†project, it is impossible to install the fill light lighting facilities on a large scale at night, and in this case, to obtain better monitoring results, it is necessary to install a high-quality low-light camera. It not only ensures the monitoring effect, but also simplifies the system composition and achieves better reliability and lower cost. In addition to these traditional monitoring areas, forests, hospitals and other places, generally also installed low-light cameras, in these occasions, the ambient lighting is not ideal, but it is not appropriate to add light sources, such as hospitals, in order to ensure the patient rest, inconvenient to fill light, etc. In order to improve the ambient illumination, you can only find a way to monitor the performance of the camera, so you need to install a low-light camera. There are also some places where there is no condition to add a light source and a low light camera is also required. For example, some outdoor sites such as construction sites, oil fields, factories, and freight yards have large monitoring areas and often no street lights. In this case, ordinary cameras cannot guarantee the monitoring effect, and low-illumination cameras are needed to ensure effective monitoring effects. In short, low-illuminance cameras rely mainly on their own performance to achieve better monitoring in weak light, making them less dependent on the external environment. For special occasions, hidden monitoring can be achieved at night. Because the reliability and performance requirements of low-light cameras are relatively high, the price is also higher than that of ordinary cameras, and the user budget should be higher. Low illumination camera classification and technical principle With the continuous expansion of application requirements, low-light camera technology is also constantly improving. There have been three low-light cameras: electronic day and night cameras, slow shutter cameras, and professional ultra-low illumination cameras (generally ICR mechanical color to black) Types of). The electronic day and night camera, also known as the electronic color-to-black camera, uses electronic circuit switching to convert color images into black and white to enhance the photographic effect in low illumination conditions. A slow shutter camera, also called a frame accumulating camera, enhances the brightness of an image by extending the exposure time. When such a camera turns on the slow shutter function, the output image is not a real-time image, as long as the shutter of the camera is slowed by more than 4 times, on the monitor. On the top you can see the more obvious image smear. Slow-shutter cameras do not enhance the image quality through the hardware performance of the machine, but rather improve the image clarity in low-light situations by sacrificing the real-time nature of the image. But for monitoring, it's important to have clear, consistent, real-time images, so frame-accumulated slow-shutter cameras are often used for monitoring static things, not for non-static applications. Professional ultra-low illumination camera (generally ICR mechanical color to black type), through the use of high-performance CCD, professional low-light circuit design, ICR filter switching mechanism and other hardware to enhance the image quality of the camera under weak light To ensure real-time, clear output of the screen. The CCD of this type of camera adopts advanced technology, and the photographic performance is 1.5 times higher than that of the previous generation CCD. Together with the performance improvement of DSP, the overall performance far exceeds the previous two types of cameras, which is called true color to black. Camera. Future development of low illumination cameras The development of low-light cameras is mainly focused on product performance and product functionality. The improvement of product performance mainly depends on better photosensitive devices, such as SONY's SuperHADIICCD, followed by better DSP technology, through DSP signal optimization, image noise reduction, and overall machine sensitivity enhancement to achieve camera performance leap. Product features are more integrated with actual needs: For example, in practice, it is easy to realize virtual focus after color-to-black, so the introduction of automatic back focus adjustment (ABF technology), stepper motor driven ICR dual filter technology (one filter is responsible for filtering out infrared light, and the other is responsible for optics). make up). Another example is the low-light camera and the infrared light, which are prone to frequent day and night switching. Therefore, AMPON has developed infrared detection and locking technology, and some manufacturers have developed photosensitive switch metering technology to protect the color-turning black camera. The conversion performance is stable. The most reasonable way to improve the low-light camera is to use hardware to improve product performance. For example, through the efforts in CCD and DSP, the low-light effect can be improved on the spot. The method of increasing the exposure time (slow shutter) or the frame accumulation technique to improve the low illumination effect often leads to undesirable effects. If a slow shutter is used, the brightness of the screen is increased due to the extended exposure time, which seems to improve the low illumination effect. In fact, the details of the captured image are blurred, so it is not advisable to extend the exposure time. Some products increase the factory default brightness value to 120 IRE (greater than the standard value of 100 IRE, 700 mV), often with good nighttime brightness, excessive exposure during the day, and poor monitoring quality. The last thing to say is digital noise reduction. This is a very effective way to suppress noise. It is through digital processing, which can reduce clutter and highlight the main body of monitoring information. The performance of the camera will be greatly improved. Low-illuminance cameras have high requirements for their important companion devices, such as high-quality lenses, and their F-values ​​can be made smaller, that is, the amount of light passing through is larger; The lens, its biggest advantage is that the day and night focus are the same, there will be no color to black defocus. 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