Megapixel HD Camera Lens and Its Development Trend

     With the development of high-definition concepts becoming more apparent, security industry technology slowly mature. For the monitoring field, the development of millions of HD is in full swing. The emergence of high-definition cameras has brought significant improvements to the image quality of security systems, such as 720p, 1080p IP high-definition cameras, 3M, 5M resolution industrial high-definition cameras, and its associated high-definition lenses have mushroomed in the market. A lot of appearance.

High-definition lenses, also known as megapixel lenses, have the advantages of high resolution, strong spectral transmission capability, and high spectral correction capabilities compared to common industrial lenses. With the increasingly fierce development of the industry's HD, the application of various types of high-definition lenses and camera products has become increasingly widespread, and megapixel lenses have become one of the focuses of industrial applications.

The camera lens is the most critical equipment of the video surveillance system. Its quality (index) advantage directly affects the camera's overall index. The choice of the camera lens is not only related to the system quality, but also related to the project cost. However, in the face of various forms of high-definition surveillance products and the ever-changing application scenarios, millions of high-definition surveillance cameras in various scenarios of complex light conditions, have to bring outstanding imaging results for the camera, which requires a high-definition surveillance camera with certain The technical content.

Aspherical lens technology is a very important technology for millions of high-definition lenses, and it is also an important guarantee for high-definition lenses. The traditional spherical lens has a congenital defect of spherical aberration, which brings about an insurmountable spot phenomenon and greatly affects the imaging quality.

The aspherical lens has good light transmittance and low refractive index. The use of an aspherical lens can replace a group of spherical lenses, so that the optical structure of the imaging lens is relatively simplified, so that it is easier to obtain a larger pass in optical paths and mechanical structures. Optical caliber. In addition, the aspherical lens enables the light of the edge portion and the light of the central portion to be focused on the same plane through the lens, so that the entire surface of the lens can be clearly and effectively used, so that the entire lens can be properly focused, and the effective communication is relatively effective. Optical caliber becomes larger.

The effective aperture of an aspherical lens increases, allowing more light to be projected onto the CCD sensor surface, which also increases sensitivity. Also, because an aspherical lens can replace several sets of spherical lenses, the camera lens can be reduced in size and lighter in weight, and because the light passes through fewer lenses, the light transmittance is greatly enhanced, and the image becomes Delicate and bright.

The important feature of aspherical lenses is that they can improve the refractive index of light on the edge of the lens and make the imaging of the lens edge better. The spherical lenses, especially the high-magnification spherical lenses, are more prone to spherical aberration and image distortion, especially the barrel distortion caused by the refraction of the light at the edge of the spherical lens. When the aspheric lens is used in a high-magnification zoom lens, due to the aspheric lens The edge incident light is corrected in the opposite direction of the spherical lens distortion, thereby effectively eliminating the barrel distortion. The aspherical design corrects for unclear images, distortion of vision, narrow visual field, and other undesirable phenomena, making the imaging more clear and delicate. It is usually used in wide-angle and ultra-wide-angle lenses, and is suitable for large-scale monitoring sites such as squares and parking lots.

The size of “transmittance” in megapixel lens technology directly affects the clarity of the lens and is an indispensable condition for high-definition image quality. "Light transmittance" refers to the light transmission capability of the lens lens, and the main decisive factor is the coating technology. The so-called lens coating is the use of vacuum vapor deposition technology to lay a thin layer of transparent film on the lens, anti-reflection film layer can produce anti-reflection effect, the higher the light transmittance, the greater the amount of light transmission, illumination requirements also The lower the backlight level, the lower the illusion and halo that can be generated due to the influence of the film layer, especially at night monitoring conditions. The level of illumination is a determinant of the quality of a night shot.

With the advancement of processing technology and the ever-increasing scope of use, a highly technical multi-layer coating technology has been produced, and multi-layer coating technology can be used to prevent reflection of light, enhance light penetration, increase the overall light transmission of the lens, and ultimately improve the image quality. . It can be said that there is no rapid development of multi-layer coating technology, and high-magnification, large-aperture zoom lenses cannot have today's development.

Recently, the multi-lens zoom lens has become the mainstream of the development of the world's lens. With multi-layer coating, the light that reaches the film surface is greatly reduced in the stray light, so that the lens discrimination rate is not reduced, and the color reproduction is not damaged. The re-evaluation of the improved film layer and the development of the most suitable coating film latest technology in various lenses is an important subject that has been studied by various manufacturers.

Lens coating seems to be a "post-processing" step, but it has already been completed before leaving the factory. Coating coatings vary according to the technology of each manufacturer, and all surveillance lens coatings are not guaranteed to be completely consistent. Therefore, understanding the coating directly affects the performance of the lens. The main types of lens coatings include nano-coatings, integrated coatings, composite coatings, and clear coatings, as well as some high-performance coatings such as BBARs and high-fidelity coatings. At present, the monitoring lenses use more BBAR and nano-coating methods. Most of the rest are used for DSC or SLR camera lenses.

High-definition is an inevitable trend in the development of video surveillance systems, and it is also an essential weapon for major security companies to compete in the deer market. As a lens that plays a key role in the imaging process, the following major issues should be noted.

First, the lens is the key to using ED lenses

The commonly used security monitoring market, 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 visible light is refracted by the lens and the focus shifts. The image shows that the edge of the object is 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, this problem has been more clearly seen, which in the material and coating accuracy on the lens has higher requirements. The higher the camcorder resolution, the more impact the lens material has on the imaging effect. High-definition power zoom lens with ED lens can provide a clearer picture for the camera when monitoring at a long distance from a long distance.

Second, choose a large-caliber design lens

Lenses with ED lenses do not completely solve the problem of remote monitoring. Usually we call an image output with a resolution of 720p or more as an HD image. According to the free choice of the market, most of them use the 1080p output format. In the field of remote monitoring, users hope to use high-definition monitoring systems to enhance the pixels of the screen, and then more clearly watch long-distance goals, but the actual results are far from satisfactory, and it is not difficult to speculate. 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 long-distance monitoring, such as high-definition SDI cameras, this camera in addition to the minimum illumination to achieve 0.3Lux at the same time, also for the field of remote monitoring added color reduction and low light image enhancement technology, making A clear picture can also be obtained when the luminous flux drops.

2, to increase the focal length of the lens when the light flux. 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.

Compared to mature analog surveillance systems, there are many technical details that HD imaging systems do not pay attention to. However, with the increasing popularity of high-definition systems, the selection of high-definition lenses will surely become more rational. At the same time, as the demand is strong, it will in turn promote the continuous upgrading and development of products.

As the trend of high-definition video surveillance has intensified, it has become the hottest topic in the monitoring industry. Major mainstream manufacturers in the industry have all launched their own high-definition products. In particular, high-definition network cameras have rich models and relatively complete peripheral equipment. The IP high-definition system solution greatly improves the video data bearing and application capabilities, greatly improves the resolution of video images, and has high scalability, centralized management, and other advantages. It has become the mainstream of current high-definition video surveillance application solutions.

Network cameras are usually divided into two types: one is that the front end is based on an analog camera to place video and network processing modules, and therefore has the same disadvantages as analog cameras: the image resolution is not high, the highest quality does not exceed D1, and the other is digital HD network camera, which is characterized by direct digital video processing and transmission via the network, to avoid the common analog camera susceptible to interference problems, can achieve a clean screen, clear and delicate picture quality, high signal to noise ratio.

In order to get the best performance of a megapixel camera, it is very important to use high-quality megapixel lenses. The quality of the optical image is a key factor in the overall image quality. As a megapixel network camera “eyeball”, a megapixel lens can provide high contrast, sharpness and sharpness for the entire image, but not a megapixel lens. Fully shows the high resolution of megapixel sensors, especially at the edges of the picture.

According to some experts, two important indicators of sharpness include resolution and contrast. Resolution refers to the ability of the lens to reproduce the details of the scene being photographed. The higher the resolution, the clearer and sharper the picture. Contrast refers to the ability to reproduce the low-contrast details and light and dark levels of the scene. The higher the contrast, the sharper the outline of the scene and the sharper edges. Rich levels, strong texture, bright tone. High-resolution and low-contrast lens, the image outline is not clear, dark contrast, dull tone, giving the impression of anti-unclear, which is also a major cause of the cold market of domestic million HD lens, so the contrast and resolution have reached At a certain height, it is the real ideal million HD camera.

In addition, the megapixel HD camera lens also has the following trends.

First, large-caliber miniaturization

In order to increase the amount of light passing through the lens, the aperture of the lens must be increased, and the brightness of the screen in the dimly-lit and night mode is better than that of a small-calibre lens. Miniaturization means that the lens has a compact structure that can be applied to different product installations and reduce the size of the product. Compared with megapixel surveillance cameras abroad, the application of aspheric technology is mature, often with the same lens, which has a focal length, a large aperture, a small structure, and high definition. Most of the major lens manufacturers in the country are slowly exploring for the early application of megapixel surveillance cameras to the development of new products, competing with foreign manufacturers.

Second, day and night are not defocused

In the intelligent transportation industry, the imager's target area is getting larger and larger, and more and more products using 1 "CMOS are available. Such products have better low-light effects than 2/3" CMOS. At present, many products do not have the function of night-vision parfocal. They rely on the flash to fill the light. Many countries do not allow the use of flash, and domestic companies have begun to discuss solutions that do not use flash.

At the same time, under the premise of ensuring the quality of the daytime, users are increasingly demanding the quality of nighttime images. On the premise of ensuring the daytime image quality, the infrared filter function can be used, and the ED (Low Refractive Index High Dispersion Coefficient) glass can better correct the color difference and improve the confocal power and image quality of day and night imaging. In recent years, major glass manufacturers have also tried to promote ED glass.

Third, noise light elimination

Noise light mainly includes stray light and ghost images. Stray light refers to the rainbow-like stray light caused by the reflection of mechanical parts. Stray light can be perfectly eliminated by the extinction treatment of the inner wall of the lens and spacers. The ghost image refers to the secondary imaging of light reflected multiple times between the lenses inside the lens. The ghost image is similar to the outline of the light object and cannot be completely eliminated. It can only be reduced as much as possible by plating the multilayer antireflection film. A high-definition multi-million surveillance camera with comprehensive performance, it should have excellent performance in the elimination of noise light in order to achieve high quality in a bright light environment, matching its reputation as a million HD surveillance cameras.

Today, the trend of high-definition has become the development consensus of the monitoring industry. With the development of high-definition, one million HDTV lens, which is one of the core components, has also shown high-speed market growth. With the development of technology and the market, higher requirements will be put on the camera. The market competition has forced the enterprises to increase their awareness of innovation. Domestic lens manufacturers must attach great importance to technological innovation and product innovation in order to improve the quality and stability of products.