Different lens brands have different definitions of megapixel lens. Taking 1.5 megapixel lens as an example, some Japanese brands define that 70% of the image area can reach 1.5 megapixel from the center of the image to the four sides of the image, and other parts can reach 1 million pixels. Such a lens is called a 1.5 megapixel lens; Some Japanese brands define that: 65% of the picture area can reach 1.5 million pixels, and other parts can reach 1 million pixels, which is called 1.5 million pixel lens; There is also a Japanese brand definition: at least 95% of the picture area can reach 1.5 million pixels, and other parts can reach 1 million pixels, which is called 1.5 million pixel lens. The definition of domestic brands is even worse. Generally, the central part can reach 1.5 million pixels, which is called a 1.5 million pixel lens. However, it is hard to say how clear the surrounding area is and whether it can reach 1 million pixels. In general, there is no uniform standard for megapixel lens at present, and the effect of clarity is still at a stage of mixed good and bad.
Coating of lens. There are many coating processes, and each lens manufacturer's coating process also has its own characteristics. The coating plays a great role in color restoration and processing of polarization and color deviation. At present, in the domestic monitoring market, the processing of color restoration has made some progress, which is basically satisfactory to users, but the processing of polarized light and color, especially glare ghost, is quite different from that of lenses applied in foreign markets.
The "light transmittance" of megapixel lens technology directly affects the definition of the lens, which is an indispensable condition for high-definition image quality. "Light transmittance" refers to the light transmittance of the lens, and the main determinant is the coating technology. At present, the highest transmittance coating in the industry is the SMC coating of Pentax lens in Japan. The transmittance reaches the highest 0.998 in the industry, laying a solid foundation for the long-term development of high-definition lens. In addition, the higher the light transmittance, the greater the light transmittance, and the lower the illuminance requirements. Especially under the condition of night monitoring, the illuminance is a decisive factor for the quality of the night lens.
In the domestic market, lens materials are generally divided into glass lens, composite material lens and resin lens, and glass lens must be used in the monitoring lens. Because resin and composite lenses are prone to aging and even deformation under high temperature and exposure to the sun, which seriously affects the image quality and lens quality.
Aspherical technology is an important factor that affects the sharpness of lens, especially the sharpness of edge part. Aspherical lens can effectively increase the light transmittance of lens edge and effectively correct the aberration blur caused by spherical lens. In practical application, few manufacturers will apply aspherical lens in the lens with small focal length. Although the aspherical lenses are exaggerated in the propaganda, they are rarely used in practice. Through the test, it can be easily seen that the lens 8 with slightly blurred image edge is not an aspheric lens, including most Japanese brand lenses. This phenomenon is mainly caused by cost. High grade glass aspherical lens uses grinding process at the edge of glass lens, while the common method is to coat the surface of glass spherical surface to make it become aspherical surface. Both aspherical processes need to increase costs, especially the former. Therefore, aspheric lenses are rarely seen in batch applications, especially in products with less stringent effect requirements. In the megapixel lens with electric zoom, because the lens itself is more expensive and requires higher effect, aspheric surface is a big selling point and a necessary technical indicator.
The concept of depth of field is a term that is widely valued when the megapixel lens will dominate the market in the future.
At present, it is impossible to see the depth of field parameter in the lens parameters, let alone the actual depth of field. But through the image after imaging, we can see which lens has a larger depth of field. high definition video camera It is required to get a very clear picture in the monitoring, and the whole picture can be clearly presented, even after being magnified, the remote scenery can be clearly seen. At this time, the lens needs to have a good depth of field. The greater the depth of field, the greater the range of near and far that can be seen clearly on the image after imaging. After the image screenshot is magnified, the remote scenery can be seen more clearly. For example, in road monitoring, the license plate number can be seen clearly after the screenshot is magnified. At present, there are only one or two manufacturers that can make a large depth of field of high-definition lens in the market, and on the basis of making full use of the large depth of field, they can keep the definition of the lens basically unchanged during the process of zooming, without refocusing. Some old Japanese manufacturers are also gradually applying new technologies in TV lens to monitoring lens.
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