Infrared night vision product selection 1, pay attention to the camera's aperture size and luminous flux
The size of the aperture of the camera's light-sensing element has become smaller, and the size of the camera's aperture on the market is generally from 1/1.8â€ to 1/4â€. When the light sensor is used with the lens, the amount of light passing depends on the size of the camera, and the aperture is small. Less light flux is accepted, and vice versa. In addition, the principle of collocation with the lens needs special attention, that is, the focal length value and the aperture aperture inversely proportional relationship, for example, 4mm aperture ratio may be f1.2-1.4, but 50mm or even 200mm aperture aperture may be only f1.8-2.2, As a result, the amount of light passing through is also affected, and the corresponding screen brightness that affects the imaging distance will also be affected when the infrared light is projected.
2, must use low-light conditions of the camera
The minimum illuminance of the camera is the lowest brightness value of the subject, and the camera manufacturer will give the lowest illuminance of the f-number of the different apertures, which is the minimum illuminance (also called the sensitivity) of this camera. If the minimum illuminance of the selected camera is higher than the maximum illuminance of the infrared projector, the effective distance of the infrared ray will be affected by the minimum illuminance, so that the projection distance will be shortened or the imaging range will be insufficient. This will result in a bright spot on the center of the screen and a dark display around the periphery. . Therefore, whether the camera is a true low-light camera is a very important indicator for monitoring the low-light environment.
3, or can use a black and white camera or day and night color / black and white camera
In addition to the camera itself has low light performance, because the photosensitive element CCD has a wide range of sensing spectrum, can sense the visible light area and a certain range of infrared light spectrum, so at night without lighting, the auxiliary infrared light source makes a clear black and white picture . The day/night color/black-and-white camera can transmit color signals. The green, blue, and red three-color video signals are separated from the output signals of the CCD photosensitive elements, and then combined to generate color television signals (the color signals only sense the visible light spectrum). With the advancement of imaging technology, it has been possible to utilize digital circuit switching to achieve the advantages of day and night color/black-and-white camera infrared sensitivity.
4, camera and lens function collocation requirements
Cameras usually have automatic electronic shutter, AES and automatic gain control, AGC and other functions, which can help to set the night vision and camera conditions, including night vision with the lens must have automatic aperture function, in order to achieve day and night illumination changes The lower camera's automatic illumination adjustment.
5, camera power collocation requirements
The power supply of the front-end equipment of the monitoring system must be designed in a unified manner. The part of the infrared projector lamp must take into account the influence of the operating current of the infrared lamp and the infrared LED on the supply voltage, and the length of the transmission cable also affects the attenuation of the DC voltage. When there is a large difference in the distance between multiple infrared lamps from the control room, the centralized DC12V power supply may cause the infrared lamp supply voltage near the control room to be high, and the infrared lamp supply voltage far from the control room to be low. Coupled with the deviation in the power supply voltage adjustment, may cause voltage or current impedance and other issues, so that the life of infrared lamps shortened or even burned. The low-voltage infrared lamp has insufficient emission power, so that the projection range, distance and brightness are insufficient, which reduces the imaging effect. Therefore, it is recommended to use the AC24V AC power supply or DC power supply as much as possible, which can ensure stable output of the DC power supply when the voltage fluctuates at AC100V-240V, ensuring the stable operation of the infrared lamp.
Infrared night vision camera installation anatomy
Different media have different transmittances and reflectivities. Therefore, different protective cover glasses, especially those with automatic defrosting coating layer, will cause some attenuation of infrared light. Special attention must be paid to construction.
The installation location of the equipment should be avoided by aiming at strong light (such as sunlight, lighting, etc.), otherwise it may easily cause excessive bright or light (not a malfunction), and it will also affect the life of the CCD.
Cameras should be kept away from humid, dusty, extremely hot, cold, and strong electromagnetic radiation.
Some infrared lamps have no irradiation distance parameters, only the number of power, which is a very vague concept, because the power consumption is converted into infrared light energy, it also includes the power heat loss, circuit heat loss, light source heat loss, filter glass Infrared light efficiency and so on. That is, the same power of the infrared projection lamp, the irradiation distance may be very far away;
Manufacturers continue to increase, but the factory inspection of related products is not easy, and the conditions of technology, detection equipment and equipment are not all different. Users should make more comparisons, carefully read the operating instructions before installation, and pay special attention to the safety of personal equipment. matter;
Consider the degree of reflection of the scene being photographed. Infrared rays have the same characteristics of reflection and refraction as visible light, so a certain distance margin should be considered when there are no good reflective environments (such as buildings, fences, signs) around the target scene.
Optional infrared projection lamp, in addition to its indicator parameters need to consider other. Most of the infrared projection lamps on the market today are in the two bands of 850nm and 940nm, and the selected camera must be able to sense the infrared light of these bands.
Weather conditions such as rain, fog, and dust are all factors that limit the distance that affects the irradiation distance. In addition, the difference between the site environment and the reflectance of the monitoring site will also make the night vision effect very different. Therefore, it must be tested before installation.
The electronic control switching device is used as far as possible, and its fuzzy logic capability can effectively control the working status of the ICR-CUT filter. Because most manufacturers use simple sensors such as photoresistor sensors to control the ICR-CUT filter and the On/Off state of the IR projection lamp, the repeated transition of its critical point is often unsatisfactory.
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