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Infrared waterproof camera soft ribs, infrared light utilization and red storm problems
What is Redstorm? Redstorm is due to the fact that the emitted infrared light contains visible light components. Infrared lamps can be completely red-free (using 940-950nm wavelength infrared tube) or only a weak red storm. The light with a wavelength of more than 700 nm is called infrared light, and the infrared light with a wavelength of more than 900 nm has almost no red-storm. The shorter the wavelength is, the stronger the red-storm is, and the higher the infrared-induction sensitivity is. There are currently two mainstream infrared lamps on the market. One is a light red storm with a wavelength of about 850 nm, one with no red storm and a wavelength of about 940 nm. The same infrared waterproof camera, the sensitivity of the 850nm wavelength than the sensitivity of the 940nm wavelength to 10 times. Therefore, infrared light with a slight red-storm at 850nm has higher efficiency and should be used as a preference for infrared night vision monitoring.
Second, the problem of life
The service life of a traditional bolt machine is generally 8 to 10 years or more, but many contractors have reported that the service life of the infrared waterproof camera is too short and the maintenance in the later period is too troublesome. The reason is that China's domestic infrared lamp production process accuracy is not high and the camera manufacturer for the one-sided pursuit of high power to increase the current load and resulting in shortened life expectancy. The IR lamps used in infrared waterproof cameras currently on the market are mainly multi-chip LEDs and single-chip LEDs. The multi-chip LED has a high current and poor heat dissipation, thus resulting in a very short lifetime. Single-chip LED production process is simple, easy to ensure quality, low heat, light emitting optical system is reasonable, is the ideal device for infrared light, the theoretical life of up to 100,000 hours or more. In general, multi-chip LEDs have a much shorter lifetime than single-chip LEDs.
Third, waterproof problem
It can often be seen that a manufacturer's infrared camera is equipped with an aluminum rain cover, which is called an "infrared waterproof camera." It is not known whether this "vest", which looks like it can withstand wind and rain, can really meet the national certification standards. However, the reporter also disassembled and tested some of the products of responsible manufacturers. The real parts of the infrared camera were firmly inlaid with a layer of waterproof rubber. In general, IP65 is an ordinary "wind and rain" level, and through IP68 is the "dive" level.
Fourth, the color problem
Infrared is the biggest assistant of infrared waterproof camera at night, but it is a kind of stray light in the daytime situation, which will reduce the clarity and color reproduction of the camera. The filter can prevent and distinguish the infrared involved in imaging. Now camera-induced infrared is generally the two methods: First, automatically switch the filter, in the visible light conditions to block the incoming infrared light; night in the absence of visible light to remove the filter, let the infrared into, this program image Good quality, but high cost, the switching device has a certain failure rate; Second, a specific infrared channel is attached to the filter, allowing infrared light with the same wavelength as the infrared light to come in. This method does not increase the cost, but the color reproduction Slightly worse.
Fifth, the problem of sensitivity
Camera sensitivity is a core part of infrared night vision monitoring. The better the sensitivity, the stronger the ability to sense infrared rays. Of course, the better the sensitivity, the more expensive the camera is. In general, infrared night vision systems within 50 meters, the use of Ql Lux camera is better; 50 meters to 100 meters of the night vision system should use 0.01 lux camera; 100 meters above the night vision system should use 0.001 Lux Above the camera. However, there is a phenomenon that the infrared waterproof camera market is nominally imaginary, and many products with an illuminance of less than a certain amount of magnitude must be marked with high values.
Infrared waterproof camera purchase attention (a) choose to leave room for the selection of infrared light irradiation distance
1. Given the minimum illuminance of the camera, it also gives the required value of the aperture F, and the zoom lens generally only gives the maximum value of 1:F, that is, the minimum value of the aperture F (the maximum size of the actual aperture), F= f/D, then D is a fixed value. When the f focal length is increased by 10 times, F becomes large (ie, the actual aperture size becomes very small). Luminous flux will be greatly affected.
2. When using an auto iris lens, automatic gain control, or automatic electronic shutter camera, the lens aperture F value also changes. For example, if there is a scene near the camera, the light is reflected back to the camera, or there is a light near the camera. At this time, the camera's sensitivity will be reduced, the size of the auto iris will be turned down, and the light flux will be greatly affected.
3. The minimum illumination given by the camera. What is the minimum illumination concept here? The video signal produced by the camera is nominally 1V with a standard value of 0.7V, while the video signal with the lowest illumination is 1/3-1/2 standard. Therefore, the image of the camera at the lowest illumination level will never be "like white."
4. The protective cover also affects the effect of the infrared lamp. In the infrared light transmission process, through different media, the transmittance and reflectance are also different. Different window glasses, especially automatic defrosting coated glass, have different attenuation of infrared light.
With the rapid development of the infrared night vision system of infrared waterproof cameras, infrared lamp production and supply manufacturers will also increase, but the red light products are not as easy as some people think, but also have different conditions in terms of technology, testing equipment and equipment, and hope that users Too much to compare, choose carefully. The infrared light waterproof camera infrared light should be read carefully for the user first, especially for the personal equipment safety precautions. Check whether the supporting aspects mentioned in the previous section meet the requirements. Whether the influencing factors that should be taken into consideration should be taken into consideration, if not meet the requirements, the equipment used can be adjusted in time.
The user should not arbitrarily increase the power supply voltage, because the infrared waterproof camera infrared light is designed to take into full consideration of its irradiance, taking into account its safety and reliability. Raising the power supply voltage may cause the infrared lamp to be burned, and it is even more desirable not to tamper with the infrared lamp. If this is done, the manufacturer may no longer be responsible for maintenance. If there is a problem with the IR waterproof camera infrared light, contact the manufacturer or supplier.
5. The sharpness of the image produced by the camera at the lowest illumination is measured by a television signal test card. The black and white stripes require a black reflectance of approximately 0% and a white reflectance of greater than 89.9%. Sometimes we do not have such conditions when we observe on the scene. For example, the reflectivity of leaves and grass is very low, and the contrast is very small, so it is not easy to obtain clear images.
(b) The most important issue in the selection of infrared lamps is the completeness of the set
The infrared light and the camera, lens, protective cover, power supply, and other sets of properties. In the design of the program, all equipment was comprehensively considered and designed, and it was considered as an infrared low-light night vision monitoring system project. Some people think about purchasing infrared light after they have bought a camera, lens, protective cover, or even power supply. This is not true. When considering the completeness, special attention should be paid to the following issues.
1. Requires size specification of infrared waterproof camera
The nominal size of the camera is becoming smaller and smaller. Currently, the size of the camera on the market is 1/2"1/3"1/4". The size of the camera is large, the received light flux is large, the size of the camera is small, and the received light flux is small, such as infrared light The nominal effective distance is tested under 1/2" camera conditions. If a 1/3" or 1/4" camera is used, the effective distance will also be affected. 1/3" camera light flux is only 1/2" 44% of the camera's luminous flux
2. The size of the lens is the same as the size of the camera and will not be repeated.
3. Camera and lens function requirements The camera has an automatic electronic shutter function, AGC automatic gain control function, the lens has an automatic iris to adapt to large changes in day and night illumination.
4. Use black and white camera or special color camera
The CCD image sensor has a wide range of light-sensing spectrum. The light-sensing spectrum includes not only the visible light region but also extends to the infrared region. With this feature, the CCD image can be illuminated with an auxiliary infrared light source without visible light illumination at night. Image sensor clear imaging. However, in order to transmit a color signal, an ordinary color camera separates green, blue, and red primary color video signals from the output signals of the CCD device, and then synthesizes the color television signals, and the photosensitive spectrum is only in the visible light region.
5 requires the use of low light camera
The minimum illuminance of the camera is the brightness value of the scene when the brightness of the subject is low to a certain degree and the level of the video signal output by the camera is as low as a predetermined value. When measuring this parameter, you should also specify the lens aperture F size. For example, when using an F1.2 lens, when the illuminance of the subject being photographed is as low as 0.02Lx, the amplitude of the video signal output by the camera is 50%-33% of the standard amplitude of 700mv, the minimum illumination of the camera is said to be 0.02Lx. /F1.2. Some camera manufacturers give the lowest illuminance at different apertures F. When the minimum illuminance of the camera is selected to be higher than that of the infrared lamp, the effective distance of the infrared light of the infrared waterproof camera will be affected.
Users should be reminded that there are two kinds of abnormalities in the minimum illumination of camera technology performances on the market. One is that the minimum illumination of the camera manufacturers is the so-called target illumination, that is, the illuminance on the CCD image sensor. It is about 10 times lower than the illuminance of the scene; the other is that some camera manufacturers or vendors falsely report the minimum illuminance. Currently on the market more economical black and white cameras (prices in the 700 yuan, some of the minimum illumination is marked as 0.01 ~ 0.02Lx) infrared waterproof camera's actual minimum illumination is only 0.1 ~ 0.2Lx, if, the use of infrared waterproof camera infrared light The minimum illumination of the camera is required to be 0.02Lx, which will inevitably affect the effective illumination distance of the infrared lamp. However, if the camera with the minimum illumination of 0.02Lux is purchased, the price may be at least twice as high as the 0.1-0.2Lx camera. At this time, there are two options: spend more on the camera and spend less on the infrared light; spend less on the camera and spend more on the infrared light. Experience has shown that when the distance is especially long, the former is more economical.
Infrared waterproof camera is a CCTV surveillance camera that integrates cameras, rain cover, infrared LED lights and other components. Its basic principle for achieving night vision is to use an ordinary camera equipped with an aperture CCD to sense the spectral characteristics of an infrared light source (that is, visible light and infrared light can be felt), with an additional LED infrared lamp as an "illumination source" at night or in micro Imaging under light conditions.