Matters needing attention when choosing a megapixel lens

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Matters needing attention when choosing a megapixel lens

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With the popularity of megapixel cameras in recent years, the demand for corresponding megapixel lenses has also increased. Beyond the traditional transportation field, other emerging industry applications such as urban surveillance also list HD systems as must device. Faced with the exquisite products of major manufacturers, how to choose a lens that suits for the security project? We will analyzes the characteristics of megapixel lenses, the functions of mainstream megapixel lenses, and how to choose them.
Megapixel lenses are currently commonly used with fixed focus, manual zoom, electric zoom, etc. For different industry applications, there are basically relatively mature applications. For example, a commonly used solution in the field of traffic capture is a fixed-focus megapixel lens. So what is the difference between a megapixel lens and a normal lens?
1. The difference in clarity
The resolution of the lens at the center of the imaging surface is the highest, and the resolution at the edge is the worst. Ordinary lens can basically meet the sharpness of the center resolution, while the sharpness of the edge is greatly reduced, and the overall sharpness can meet the requirements of 440,000 pixels of ordinary cameras.
There are three key factors that determine the sharpness of the lens:
A. the lens material and purity. The less impurities in the lens, the less interference light it produces, and the clearer the picture.
B. The grinding precision of the lens. The grinding precision of the lens is determined by the grinding equipment.
C. The coating precision of the lens. The best control of the coating process is also one of the determinants of lens clarity. 
In addition, the megapixel lens adopts aspherical lens, which can reduce aberrations, and achieves a miniaturized design while improving the sharpness compared with ordinary lenses; through special optical design technology, the image quality from the center of the image to the peripheral part is high. The resolution, high-contrast picture, the resolution is about 2.5 times higher than the traditional lens, even when the image is cut or zoomed in, it can still ensure high image quality.
2. Difference in spectral transmittance
The spectral transmittance of the lens also contributes to the improvement of picture clarity. The transmission of wide frequency light will greatly increase the amount of light received by the camera's target surface. It can enhance the contrast and brightness of the picture, and the details of the picture are more abundant.
3. Difference in spectral correction ability
Only the wide-spectrum transmission ability is far from enough for high-definition imaging. If the spectral correction ability of the lens is insufficient, it will make some wavelengths of light unable to accurately image on the camera target surface, resulting in the production of virtual images. This kind of technology cannot be achieved by ordinary lenses through coating. 
So what should we pay attention to when choosing megapixel lenses?
1. Correspondence              
High-definition cameras have just entered the market, and the resolution is often around 2 million pixels. Engineers often feel that the cost of megapixel lenses is too high. The high-definition cameras are equipped with standard-definition lenses, and the effect is decent, and the clarity of the standard-definition system has been greatly improved. Therefore, many systems have blurred pictures, especially when the center of the picture is clear and the edges are blurred. The debugging cannot solve the problem. With the introduction of 3 million, and 5 million cameras into the market, engineers have gradually learned about megapixel lenses. Start rationally choosing the right lens according to the camera. 
Megapixel lenses are divided into definitions. Common ones are 1.3 million pixels, 2 million pixels, and 3 million pixels. High-end products have 5 million pixels. Individual manufacturers have already achieved 10 million pixels. Then when choosing a lens, you should choose a lens product with the same or higher pixels according to the highest resolution of the camera. For example, a 2 million pixel capture CCD camera commonly used in traffic should be selected according to the actual application environment of 25mm or 35mm corresponding to 2 million pixels. At present, the definition of common electric zoom lens generally corresponds to 1.3 million pixels. The needs for telephoto and high-definition lenses are diverse. 2. According to the camera application, select products that match the function              
In some security projects, the camera needs to cooperate with infrared light during use, so a lens with IR function should be used. Get a brighter picture at night. At the same time, it also reduces the problem of virtual focus at night. For more demanding environments, such as with laser lights, for long-distance target monitoring, it is necessary to choose products made with ED (ultra-low dispersion) lenses. Ensure that the non-visible light wavelength can still achieve a transmittance of more than 60% when the wavelength is 900um. 
3. Use the auto-focus function lens to solve the delay problem              
At present, most of the HD cameras on the market use IP output, and the encoding is completed inside the camera. After being transmitted through the network, it needs to be decoded in the monitoring center before it can be displayed on the screen. Everyone knows that the camera will cause a delay in the encoding process, and the network transmission also has a delay. The more equipment and the more the forwarding times, the longer the delay. The decoding process of the monitoring center will also cause delays. These delays are superimposed. Will seriously affect the operation of monitoring personnel. For fixed-focus products, this part of the delay has relatively little influence. As for the system using a power zoom lens, it is embarrassing to use. On the one hand, it is a high-definition system. On the other hand, due to the above-mentioned delay superposition, the picture is always unfocused, or the focus time is too long to quickly capture the target. In this case, choose a product with auto-focusing function is necessary. 
The automatic focusing lens is used to automatically complete the focusing process at the front end, so that the picture transmitted back to the center is always clear, which can bring the following benefits to the high-definition system:
1. Reduce the focus operation of the lens by the operator and extend the service life of the motor.
2. Because the picture is always clear, the camera can have a higher rate and higher compression ratio when encoding, which reduces the resource occupation of transmission and storage;
3. It shortens the target capture time, so that the monitoring personnel can Browse more pictures, thereby improving the effect of the monitoring system.
With the popularity of high-definition cameras, more and more systems require the access of high-definition lenses. Major lens manufacturers have launched high-definition products with different focal lengths. Provide engineers with more choices. With the application of ED lenses, auto focus and other functions in high-definition lenses, the difference between high-definition electric zoom lenses and standard-definition products is getting smaller and smaller. The future trend will be a great integration of products, and HD products will gradually replace existing SD products and become the mainstream of the market.
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