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What kind of lens is an HD lens
For high-definition cameras, you can use ordinary lenses called megapixels, you can also use millions of HD lenses, and you can also use 3 million HD lenses. In the case of the same camera, the final performance of the screen and the resolution of the lens A decisive role.
According to the technical indicators released by some products, the general “megapixel camera†has only 1 million pixels of its center resolution, and the surrounding area will decay to only 50-600,000 pixels. At present, the mainstream “megapixel HD†lens on the market, the published technical indicators are usually an imaging circle with a radius of 70% of the field height, a resolution of 3 million pixels, and resolution beyond 70% of the imaging circle of the field height can reach the resolution. More than one million pixels.
Currently, there are only a few “HD†lens products on the market that can do: an imaging circle with a radius of 80% of the field height, a resolution of 3 million pixels, and an 80% field circle around the imaging circle, and the resolution remains. More than 2 million pixels. It is not difficult to see: Because there is a huge spread between HD lenses and ordinary lenses, there are more and more confusing concept lens definitions on the market, making consumers look at the flowers. But after unveiling these "beautiful" veils, the high prices are not necessarily high quality products.
Today, with the development and maturity of high-definition cameras, high-definition monitors, and network transmission technologies, the CCTV security market is also entering the high-definition era. In such a wave of technological upgrading, the lens should not become a stumbling block in the development of high-definition CCTV market, so a clear and unified "high-definition lens" indicator has become a pressing matter of the moment. 
High-definition lens four issues of concern
It seems that as long as the monitoring system is mentioned, people immediately think of HD. 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. Please look down.
First, the lens used ED lens is the key commonly used security monitoring market, we are more often used fixed-focus or manual zoom lens, because the monitoring distance is closer, 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. This is reflected in the image. 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 use ED lens lens can completely solve the problem of remote monitoring? Normally, we output images with a resolution of 720 p or higher 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 sharpness, but the picture's color reproduction capability, sharpness are greatly attenuated, the output image clarity is even worse than the D1 picture quality, or even not as 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 light 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 field of remote 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. The user pays attention to the HD system. It is not only concerned about whether the screen can be clearly seen during the day. The monitoring performance at night is also the focus of attention. 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 adapt to the current high-definition products in order to improve picture performance, often using a large target surface of the photosensitive chip. 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" products. 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. This can guarantee that there will be no vignetting. For sizes larger than 1/1.8", you should choose 2/3" or 1".
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.
High-definition camera with high-definition lens has been the trend of product application in the past two years. The functional requirements and application capabilities of the surveillance application market are also increasing. With the development of high-definition cameras, the camera has been leading the development of the lens, making high-definition With megapixel lenses there is still a lot of room for upward development.