In 2015, the security surveillance industry continued to develop rapidly, and the pace of high-definition video surveillance went deeper and deeper. At the same time, high-definition also promoted the networked and intelligent video surveillance, accelerating the progress of the era of high-definition surveillance. Before the popularization of high-definition, monitoring equipment users often encountered such a situation. When handling evidence and collecting clues, there were surveillance cameras on the scene, but after viewing the video, it was found that the video screen was very poor, the characters were blurred, and they were full of snowflake noise. At night, it is even dark, and it is difficult to extract valuable information. These videos are even dubbed "Impression oil paintings composed of Tetris". 1. Development status of surveillance camera In recent years, with the introduction of new security technologies, high-definition technology has been widely used, and high-definition cameras have gradually replaced standard-definition cameras and become the mainstream of the market. HD cameras can provide users with better picture quality and more detailed information, reducing the "impression oil painting composed of Tetris" mime. The high-definition effect of the camera is not only dependent on higher-pixel photosensitive devices, better ISP technology, and more efficient storage technology. The high-definition lens is also a key technology. Without a matching high-definition lens, the high-definition camera cannot play the high-definition effect. High-definition lens, also known as super megapixel lens, has the advantages of high definition, strong spectral transmission capability, and more precise workmanship compared to ordinary lenses. Generally, the resolution of the center of the lens imaging circle and 0.7 field of view is selected as the criterion for judging the sharpness of the lens. The center of the imaging circle and 0.7 field of view can reach more than 1000TVLine, which is called a high-definition lens. Since 2010, high-definition lenses have maintained an average annual growth rate of more than 10%. At present, the main domestic CCTV high-definition lens market brands include Hikvision, Phoenix Optics, Fujian Fuguang, Xiamen Liding and other domestic brands, as well as Fujinon, Tamron, computar, Japanese brands such as Pentax. Due to the rapid progress of domestic optical technology and the localization trend of security lenses, domestic brands represented by Hikvision gradually replaced Japanese brands and began to occupy more market share. With the precise grasp of market demands and the unremitting pursuit of performance and quality, Hikvision's high-definition lens products have covered many major products such as 1 / 2.7 "HD infrared zoom, 1 / 1.8" HD infrared zoom and ITS HD. Series. Figure 1 Hikvision HD lens Two, four core technologies The lens itself is high-precision optics, especially for high-definition lenses. The reason why the HD lens has better HD performance is inseparable from the key technologies used: 1. Ultra-precision molded aspheric technology The traditional spherical technology has developed to this day, and its design technology and manufacturing process are quite mature, and it has been widely used in almost all fields of the optical industry. However, when designing complex high-definition lenses, the imaging effect of spherical technology cannot reach the best. Aspheric technology can correct spherical aberration and greatly improve the imaging quality of the lens. The shape of the aspherical lens is accurately calculated and molded by a precision machine. A single aspherical lens can achieve the effect of correcting aberrations of multiple spherical lenses. Lenses using ultra-precision molded aspherical lenses can effectively reduce the lens volume, while making the lens imaging clearer, better light transmission, and more accurate color reproduction. Figure 2 Aspheric technology 2. Multilayer broadband AR coating technology Multi-layer broadband AR coating technology can maximize the light transmittance of the lens and reduce the residual reflection of light on the surface of each optical lens. This technology can suppress the visible light reflectance of the glass and air interface to less than 0.5%, while reducing the reflectance of near-infrared light to about 1%, as shown in Figure 3. The high-quality coating reduces unnecessary stray light and ghost images on the image, effectively improves the transparency of the picture, and also ensures a reliable high-definition effect. Figure 3 Comparison of ordinary single-layer AR coating and multilayer broadband AR coating 3. Ultra-low dispersion material technology Ordinary surveillance lenses will also be designed to correct the aberrations of different wavelengths of light (red, green, and blue), but they usually focus the red and blue colors of the two ends at the same position, but with the green focus in the middle. It still does not coincide, that is, there is aberration of the secondary spectrum, which limits the imaging quality of the lens to be further improved. In order to correct the secondary spectrum, such as Hikvision surveillance high-definition series lenses, ultra-low dispersion optical glass materials are widely used. With its dispersion characteristics different from conventional optical glass, red, green, blue and other colored lights can be focused to the same On a plane, as shown in Figure 4, the lens HD performance is better. Figure 4 Ultra-low dispersion glass corrected secondary spectrum 4. Precision zoom cam design technology For high-definition zoom lenses, the imaging quality depends largely on the accuracy of the zoom cam. Through the rotation of the cam, the lenses of the zoom and focus groups are moved back and forth, so as to realize the continuous change of the focal length and the adjustment of the focus point. If the accuracy of the cam is not good, in the process of zooming and focusing, it is inevitable that the optical axis of the lens will shift or tilt, resulting in a serious deterioration in imaging quality. Hikvision high-definition series of surveillance lenses adopt precision zoom cam design technology, which can ensure good cam manufacturing accuracy, ensure the imaging quality during zooming and focusing, and also ensure smooth adjustment without losing the sense of damping. Figure 5 The zoom cam used by Hikvision HD lens Open Frame For Capacitive Touch All-in-one ShenZhen GreenTouch Technology Co.,Ltd , https://www.bbstouch.com
