Infrared waterproof camera purchase and common problems
In the security electronic monitoring system, with the increase of people's awareness of prevention, the need for 24-hour continuous monitoring of television monitoring in important places, and the maturity of infrared imaging technology, the usage rate of infrared waterproof cameras is getting higher and higher, and has gradually developed into a kind of trend.
Purchase of infrared waterproof camera
1. While giving the camera low illumination, also give the required value of the aperture F, and the zoom lens generally only gives a large value of 1: F, that is, a small value of the aperture F (large value of the actual size of the aperture), F = f / D, then D is a fixed value, and when the focal length of f is 10 times larger, F becomes very large (that is, the actual size of the aperture becomes very small). Luminous flux will be greatly affected
2. When using automatic aperture lens, automatic gain control or automatic electronic shutter camera, the lens aperture F value will also change. For example, if there is a scene near the camera that reflects strong light back to the camera, or there is light nearby to illuminate the camera, the sensitivity of the camera will be reduced, the size of the automatic aperture will be reduced, and the luminous flux will be greatly affected.
3. Low illumination given by the camera. What is the concept of low illumination here? The video signal generated by the camera is nominally 1V, the standard value is 0.7V, and the video signal value at low illumination is 1 / 3-1 / 2 standard plant.
4. The protective cover also affects the effect of the infrared light. During the transmission of infrared light, the transmittance and reflectance are different through different media. Different window glass, especially the automatic defrost coated glass, has different attenuation of infrared light.
With the rapid development of infrared waterproof cameras and infrared night vision systems, the production and supply of infrared lights will also increase, but red light products are not as easy as some people think, and conditions are different in terms of technology, testing equipment, etc., I hope users Compare more and choose carefully. Users should read the instruction manual carefully before using the infrared waterproof camera infrared light, especially to ensure the attention of personal equipment. Check whether the compatibility mentioned above meets the requirements and whether the influencing factors to be considered are taken into account. If the requirements are not met, the equipment used can be adjusted in a timely manner.
Users should not increase the supply voltage without authorization, because the infrared waterproof camera infrared lamp is designed with both its full irradiance and reliability in mind. Increasing the power supply voltage may cause the infrared lamp to burn out, and the infrared lamp should not be dismantled and changed without authorization. If this is done, the manufacturer may no longer be responsible for repairs. If there is a problem with the infrared light of the infrared waterproof camera, you should contact the manufacturer or supplier.
5. The sharpness of the image produced by the camera at low illumination is measured with a TV signal test card. The black and white stripes require black reflectance to be close to 0% and white reflectance to be greater than 89.9%. And we sometimes do not have such conditions when observing on the spot, for example: the reflectance of leaves and grass is very low, the contrast is small, it is difficult to obtain a clear image.
Infrared waterproof camera fog and water vapor problems
Problems such as mist and water vapor can be solved in the following ways.
In one case, mist appears inside the machine:
The formation of fog and frost is due to the condensation of saturated water vapor in the air, and the formation of frost and fog due to the strong and weak cold environment. During the working process of infrared cameras, especially indoor cameras, fog or frost may be formed on the window glass of the protective cover due to fog or water vapor, etc., causing the camera to be unable to see objects, which directly affects the monitoring effect.
Each company's solution to this problem is also different. Add defrost circuits, open air holes, fill nitrogen, add fans, put desiccants, etc. The methods are different, and of course the effects are different. Some can solve the problem, and some can't solve the problem. However, from a basic point of view, it is very important to strictly control the cleaning of the materials to minimize the presence of volatiles. For example, the PCB board must not have residual flux, and the light-shielding rubber sleeve is made of silicone material.
Two cases, frost and fog appear outside the machine:
The camera works in a high humidity environment, and the window glass of the protective cover is prone to dirt, which will cause the camera's vision to be blocked.
Solution: 1. Add a wiper to the protective cover and clean the glass by controlling the wiper. 2. Use invisible wiper window glass. Compared with ordinary window glass, invisible wiper window glass has the function of repelling water and dust.
Later, for high humidity conditions, some requirements for enclosure sealing
If the infrared waterproof camera is used in the north, there will be a large temperature difference between the inside and outside of the machine, and the front lens will be fogged. Therefore, it is required to have a good seal inside the machine, and the protective cover must also have good rain resistance .
At the current stage, there are technical problems in the sealing performance of continental technology, such as the design of the housing, and the places where joints and screw interfaces are leaking.
How to do a good job of sealing? The basic solution is this:
First, add a waterproof rubber sleeve, add a water pad at the interface, play a waterproof role, the effect is ideal.
2. Add waterproof glue at the screw port of the wiring to enhance the water resistance.
Third, the infrared waterproof camera uses an aluminum alloy shell to improve the accuracy of the interface, and the use of silicone material adhesion, the effect is also ideal.
Infrared waterproof camera image problem
Why does the infrared waterproof camera flicker? As mentioned before, when the illumination intensity is lower than the threshold, the infrared light turns on. It turns off when it exceeds the threshold. Let's consider the situation when the illumination intensity is slightly lower than the threshold: the light sensor detects that the illumination intensity is slightly lower than the threshold, and controls the infrared light to turn on. After the infrared light is emitted, the detected illumination is increased (plus the reflection Back to the infrared light), and exceeds the threshold, control the infrared light to turn off-causing the detected illuminance to decrease, and control the infrared light to turn on again. This keeps going back and forth, causing the image to flicker. This situation is due to the principle, not normal, at least not the quality of the product.
The first is to extend the use time of the infrared light of the infrared waterproof camera, which affects the service life of the product;
The second is to turn on the infrared light for situations where color images can also be produced, which will cause the image quality to decrease at this time;
The third is to generate infrared eyes on color images (infrared eyes are also determined by principles, a phenomenon that people do not want to see). If the threshold is low, the infrared light may not be turned on in time when supplemental lighting is needed.
At present, ordinary infrared waterproof cameras generally use a light-sensitive element to detect the illumination intensity of the surrounding environment, and generate a control signal according to the threshold determined in the design parameters to realize the turning on of the infrared light. The level of the threshold depends on the environment used, the preferences of the user, and the importance of the designer in considering various factors. The products of different manufacturers are different. Such as 20, 10, 5 Lux. If the threshold is high, the turn-on time is earlier. It is possible that the camera has not yet switched from color to black and white, and the infrared light is turned on. This has three disadvantages.
So how to solve this problem?
The environmental illuminance detected by the photosensitive element is slightly lower than the threshold value, which is the problem. There are two cases:
First, at a certain point in the dusk, for a short time, this problem occurs. If you don't want to increase the cost, use a general heart film. Our idea is to explain the reason to the user and tolerate it.
2. This problem is solved when the lighting intensity is stable.
1. Change the threshold.
In the same type of product, the threshold is also different, and there is dispersion. Changing the product may solve the problem.
Manufacturers provide products with different design thresholds for replacement.
Products with higher threshold design parameters are less likely to flicker.
2. Change the environment
Change the intensity and angle of the lighting.
Slightly change the installation angle of the infrared waterproof camera, move up, down, left and right, the illuminance detected by the detector will change a lot, and it will leave near the threshold to solve the flicker problem.
3. Use high-quality low-light camera cores with backlight compensation and anti-glare, especially dedicated IR lenses;
In addition, when people or other objects reflect infrared light near the infrared waterproof camera, the detected illuminance will change repeatedly, causing flicker. For example, during the demonstration test and inspection, the camera is installed at a low position, and when the object is close to the camera.
This is not a problem. When the infrared waterproof camera is in the normal installation position, this phenomenon naturally disappears. For example, just be careful not to reverse the infrared light directly to the photosensitive element from a very short distance.
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