The fog-penetration function of SONY FCB-EV7520 is as follows: when there is fog around the subject and the contrast is low, the fog-penetration mode will make the subject look clearer. Its fog-penetration function has four choices: low, medium and high. When it comes to the function of fog penetration, it is generally known that the camera with fog penetration function can output a clearer picture even in haze weather. Now, with SONY FCB-EV7520 as the introduction, I will talk about the principle of camera fog penetration.
SONY FCB-EV7520 with HDMI HD interface board
1. Classification and principle of fog Transmittance camera
1, optical fog penetration
Natural light consists of a combination of different wavelengths of light waves, the visible range of the human eye is roughly 390nm-780nm, wavelength from long to short respectively corresponding to red, orange, blue, green, orange and purple seven colors, wavelength less than 390nm called ultraviolet, wavelength greater than 780nm called infrared. Fog, smoke and other small particles in the air have a blocking effect on the light, so that the light can not be reflected through, so the human eye can only receive visible light is unable to see the object of the back door of the smoke fog. The longer the wavelength, the stronger the diffraction ability, that is, the stronger the ability to bypass the barrier. However, infrared ray has a longer wavelength, it is less affected by the aerosol during propagation, and can pass through a certain concentration of haze and soot to achieve accurate focusing, which is the basis of optical fog penetration.
2, electron through fog
With the diversification of products, the market is also increasingly mature, the emergence of the integrated movement function of fog penetration can be said to be of great significance for the popularity of fog penetration products. Most of the integrated movement released in recent years adopts pure electronic fog-permeating, which is processed by embedded FPGA chip. It can output color images. This algorithm can distinguish the distance and near-range fog intensity and other factors, and improve each pixel to achieve the best regional effect. It is different from the overall improvement of picture contrast in the past, and there is no delay. Moreover, the high-speed computing of the chip will certainly produce noise points, which is more prominent at night when the light is insufficient. The integrated movement generally adopts CMOS sensor and large aperture lens to achieve good low-light effect, on the other hand, it is easier to achieve high-definition fog penetration.
SONY FCB-EV7520 integrated movement adopts 1/2.8 TYPE Exmor R CMOS sensor and F1.6 large aperture, which can achieve good low-light effect, and it is easier to achieve high-definition fog penetration effect, which belongs to the category of pure electronic fog penetration.
Camera fog penetration function
Two, the camera to achieve the three elements of fog penetration
In the range of invisible light, there is a frequency of light can penetrate the fog, but because the wavelength is different, so it needs to be processed on the camera, in order to achieve the purpose of focusing it, at the same time, it also needs to be redesigned on the camera, used to image the invisible light of this frequency, because this invisible light has no corresponding visible color map, So the image presented on the monitor is black and white.
(1) Lens with chromatic aberration compensation
The design of lens is very important in order to get a better effect of fog penetration. In order to ensure that the visible imaging system can get ideal images before and after the fog penetration, the lens must ensure that it has a high transmittance in both visible and near infrared bands, and the color difference is corrected during the switching process of the two bands to ensure that the focal length is not adjusted after the switching.
The central wavelength of the common lens is between 500 ~ 600 m, and the lens in the fog transmission system needs to be 500 ~ 600 nm and 780 ~ 900 nm to obtain a very high transmission rate. Therefore, the lens adopts multi-layer coating technology, and the transmission rate of 500 ~ 900 axis is more than 80%. In principle, it is natural that the wider the available near-infrared band, the better, but it may also be affected by the difficulty of the lens optical path design and the sensitivity of the sensor and slightly deviated.
(2) CMOS with high near infrared sensitivity
Ultra-high sensitivity CMOS camera with good frequency response curves from visible band to near infrared band is a necessary condition for an excellent system. In this way, visible band and near-red band can be used separately with only one camera through the method of transforming the filter. In order to facilitate the use of visible band to improve the clarity of the image and use the near infrared band to penetrate the mist to increase the purpose of observation distance.
(3) Image processing of black level stretch
The scattering of water vapor and solid particles over the ocean and city causes the distant color plain, gray and white light within the visible distance can not go beyond the visible distance. The use of filter undoubtedly plays a small role, but to achieve the clearer the image of the remote observation, the better the better the use of the distance. It is necessary to use electronic processing technology to filter out the interference signal of the gray and white film caused by scattering, and then process the useful white or black and white signal to obtain the excellent image signal of distant objects.
SONY FCB-EV7520 pure electronic fog penetration function, using the advantage of aperture lens and chip algorithm and other means combined with each other, according to the image impurity concentration automatic adjustment, compensation image chromatism, you can get a clearer image close to the real scene. Widely used in security monitoring, UAV, snapshot kiosk, transportation and other industry products.