High-definition monitoring easily overlooked four major issues
In recent years, the concept of high-definition surveillance has been scolded. In addition to urban surveillance, smart buildings, and bank monitoring, which we often see, maritime surveillance and forest fire monitoring are all focused on high-definition surveillance systems. It seems that as long as the monitoring system is mentioned, people immediately think of HD. So can HD monitoring really bring us an HD experience? The lenses that play a key role in the imaging process are those that are easily overlooked.
First, the lens is the key to using ED lenses
Commonly used monitoring markets, we are more often used fixed-focus or manual zoom lens, because the monitoring distance is close, the lens focal length is generally used within 50mm. This scene has almost no requirement on the lens's anti-dispersion performance. However, once a power zoom lens is used to monitor distant objects, the problem of dispersion is highlighted. (Dispersion is the phenomenon in which light of various wavelengths in the visible light is refracted by the lens and the focus shifts. The image shows that the edges of the object are blue. Color or red color bar). Originally in the analog surveillance system, due to the large pixel size, the problem of dispersion is not very prominent, and it will only be demonstrated when the 300mm focal length is configured. In the era of high-definition, in the commonly used 120mm focal length of the electric zoom lens, it has been more obvious that this problem can be seen. This imposes higher requirements on the lens in terms of material and coating accuracy. The higher the camcorder resolution, the more impact the lens material has on the imaging effect.
Second, large-caliber design is the key
Then is it possible to completely solve the problem of remote monitoring by using ED lens lenses? Normally, we output images with 720p or higher resolution as high-definition images. According to the free choice of the market, most of them use the 1080p output format. In the field of remote monitoring, users want to use high-definition monitoring systems to improve the picture pixels, and then more clearly watch long-distance goals. According to our actual experience, using high-definition system viewing, not only does not make the picture clarity, but the picture's color reproduction ability, sharpness are greatly attenuated, the output image clarity is even worse than the D1 picture quality, and even not as good as the analog camera . When the focal length is elongated, the screen becomes a black and white image, and the sharpness is seriously degraded. The effect of the image is worse than that of the Hitachi ultra-low illumination camera with the same lens. This is actually not difficult to understand. Most of the high-definition cameras we use today are CMOS chips, and the luminance performance can only reach 0.5 Lux. The telephoto lens in the process of focal length changes, the luminous flux will also change, the longer the focal length, the worse the luminous flux. When the focal length is stretched to the maximum, the luminous flux is reduced to the weakest. Although it is during the day, it is equivalent to the camera being shaded in the front, leaving only a small hole to transmit light. In this case, ordinary HD cameras will suffer from picture quality degradation due to insufficient illumination. To solve this problem, we can start from two aspects:
1, using high-definition cameras designed for remote monitoring, such as high-definition SDI camera, this camera in addition to the minimum illumination to achieve 0.3Lux at the same time, but also for the long-distance monitoring added color reduction and low-light image enhancement technology. This allows a clear picture to be obtained even when the luminous flux drops.
2. Improve the luminous flux of the lens when the focal length is elongated. Once the lens is produced, the range of luminous flux is determined and cannot be changed. Therefore, we must choose those products with long-focus time luminous flux performance when selecting the lens. According to the optical relationship of the lens, F (inverse ratio of luminous flux) = f (focal length)/D (effective aperture before the lens). The F value is inversely proportional to the luminous flux. The smaller the value, the better the luminous flux performance. Then, in the case of the same f, choose the lens with the larger effective aperture, the better the screen effect is.
Third, the IR function is easily overlooked
Users pay attention to high-definition systems, not only to pay attention to whether clear images can be obtained during the day, but also to monitor performance at night. In the HD system, the IR function is generally forgotten. However, with the improvement of the sensitometric performance of high-definition systems, the IR function has gradually been recognized by users in all-weather monitoring systems. Especially with a power zoom system, the IR function is crucial. For a system with an auxiliary light source such as a laser illuminator, whether the IR function is available will directly affect the ease of use and availability of the system.
Fourth, large target surface design of the camera to a high degree of adaptation
At present, high-definition products often use large target light-sensitive chips in order to improve the picture performance. Often these cameras encounter a lot of confusion when configuring the lens. The lenses produced by most lens manufacturers still use the dimensional standards of the past analog era, namely 1/2" and 1/3". The actual conditions of camera specifications on the market use the following two types:
1, use more than 1/3 "and less than 1/2" products, such as 1/2.5", 1/2.7", 1/2.8". When these cameras are equipped with HD lenses, if you use 1/3" lens, it will It will make the picture produce a "dark corner." Therefore, the current 1/3" high-definition lens, especially the power zoom lens has become almost a tasteless. In this application, users are using more than 1/2" products. For example, KOWA's 7.5-127mm product.
2, using more than 1/2 "products, such as 1/1.8", 2/3". Camera with 1/1.8" sensor in the configuration of high-definition lenses, if the use of 1/2" products, more or less Vignetting may occur, so when the customer chooses to configure, try to use a 1/1.8" mirror head. This will ensure that there will be no vignetting. For sizes greater than 1/1.8", you should choose 2/3" or 1" and other specifications.
In a word, there are many technical details that are not taken seriously for the high-definition imaging system compared to the mature analog monitoring system. While details determine success or failure, excellent imaging systems will consider more. With the increasing popularity of high-definition systems, the selection of high-definition lenses will be more rational, and with the demand for strong, will continue to promote the continuous upgrading and development of products.
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