Eight Problems of Infrared Night Vision Surveillance System

When technology arrives, an infrared night vision system over 100 meters is not that difficult. When technology arrives at home, it means that you must master infrared light technology, infrared sensor camera technology, and infrared sensor lens technology. All three are indispensable. The "nighthawk" system on the market now has a distance of more than 500 meters and a power of less than 50 watts. The 1,500-meter night vision system under development will be available in March next year.

The development direction of video surveillance lies in the outdoor, and the development direction of outdoor surveillance lies in night vision, and the development direction of night vision lies in infrared technology. This trend is more and more obvious. In the field of infrared night vision, Chinese companies have taken the lead in the world, and some advanced technologies have made foreign counterparts far behind. However, this is a new industry after all. A large number of low-quality products flooded the market, affecting people's trust in infrared night vision products. In addition, there are still some leading companies in the past, because the phenomenon of persisting in profits, standing on the ground in technology, and being abandoned by the market soon is worth thinking deeply.

This article deals with common technical problems and confusions in infrared night vision surveillance. It is an opportunity to communicate with readers and contractors. It also hopes to provide valuable insights for engineering companies and users of infrared night vision surveillance. reference.

Looking at the north and south of the sky, so many manufacturers of infrared lamps vowed to claim their own infrared light irradiation distance is 100 meters or 200 meters and so on, also invented the term "foot meters", which misled the engineering firm as if the infrared light There is a fixed irradiation distance. Regardless of how the manufacturers advertise, the contractor is unbelieving and believes that a nominal 100 meters infrared lamp can barely use 50 meters. A lot of responsible engineering companies, but also bought numerous infrared lamps can not meet the requirements of users, it is really bitter words.

So, infrared light does have a fixed exposure distance? Infrared night vision monitoring only involves infrared light technology? Numerous facts prove that the answer is negative. In fact, as far as any infrared lamp is concerned, there is absolutely no fixed irradiation distance. Any practice of marking the irradiation distance of an infrared lamp in isolation is very unscientific. There are also fairly professional people and manufacturers who have come to realize that in order to achieve the desired effect of infrared lighting, they need excellent cameras and infrared lenses with excellent performance. The most commonly heard argument is that it requires an infrared-sensing camera of 0.001 Lux or more, preferably black and white; it needs a special infrared lens, and its infrared transmittance reaches over 95%. The problem is that any professional engaged in optical research and manufacturing knows that these so-called lenses with an infrared transmission rate of more than 95 percent really need to achieve 95 percent or more of infrared transmission. The rate is more difficult.

This article will start from the eight common problems in infrared night vision surveillance system, aiming at the difficulties that users often encounter in the use of this type of products to develop a perspective unique analysis, will be for the majority of engineering companies to monitor the infrared night vision further Cognitive belts have valuable references.

Red storm problem

Some manufacturers have been able to create red-threatening infrared light as a technical issue to promote, as if there is a red storm is low-tech, no red-storm is high technology. In fact, whether or not there is a red storm is just a matter of choice. It is not a technical problem. Light with a wavelength of more than 700 nm is called infrared light, infrared light with a wavelength of more than 900 nm is almost no red-storm, and the shorter the wavelength is, the stronger the red-storm is, and the higher the infrared sensitivity is. Currently, there are two mainstream infrared lamps on the market. One is a light red storm with a wavelength of about 850nm, one with no red-storm and a wavelength of about 940nm. With the same camera, the sensitivity at 850 nm is 10 times better than at 940 nm. 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.

Life problem

The service life of the camera can reach more than 10 years. Can the life of the infrared lamp reach this level? To answer this question correctly, we must first understand the current manufacturing principle of infrared lamps. At present, there are mainly three manufacturing modes of infrared lamps: 1, halogen lamp, 2, multi-chip LED, 3, single-chip LED. Halogen lamps are a more traditional technology, with high energy consumption, large heat generation and short service life. Due to their low use efficiency, they are expected to gradually fade out of the market.

Multi-chip LEDs also come in two forms, one containing 4 to 8 chips; the other is an array of light-emitting chips containing 10 to 30 chips. Why do multiple chips? Some of the theories from the manufacturers are: Infrared light is not irradiated enough because of insufficient energy, more chips are gathered together, of course, the energy is large, and it is taken for granted that the irradiation distance is further away. Of course, farther distance requires more energy, but it is not how much infrared light the infrared light emits, how much infrared light the camera can receive.

Multi-chip LEDs have no light-emitting focus due to their inherent structural defects, their luminescent optical system is unreasonable, and their useful light efficiency is relatively low (of course, they are several times stronger than halogen lamps), and their advantages are not effectively exhibited. For example, an arrayed LED with a current of 1000 mA or more is basically just a penny coin size, and heat dissipation becomes a problem. The most afraid of LED is high fever, ah, not bad it is strange. At the same time, the production requirements of multi-chip LEDs are very strict. Each chip cannot have a slight difference in performance. Otherwise, if one chip is broken, the whole machine is completely finished. In general, the life of multi-chip LEDs is far from enough compared to single-chip LEDs.

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. So, is the lifetime of all single-chip LED lights good?

In fact, far from it. There are many reasons for this, such as some LED chips are very low level, impurities exceeded; some production processes but off, there is leakage phenomenon; some use of super power, rated 20mA, but use more than 50mA; some without protection circuit, or Unreasonable circuit design, these will lead to a single chip LED infrared light quickly broken.

To ensure the longevity of infrared lamps, high-grade LED chips must be selected first. High-grade chips have large power, good consistency, high luminous efficiency, and low heat generation. A high-grade LED is 10 times better than ordinary LED's, but it is also very expensive. Second, the optical system design must be reasonable, the light should be uniform, the utilization rate should be high, and the heat dissipation should be fast. Third, we must strictly control the operating voltage. The LED is very sensitive to voltage, and the LED die will burn off when the voltage is slightly higher. However, if the voltage is lower, the amount of light emission will be greatly reduced. It is best to match a high quality switching power supply. The AC input voltage is preferably regulated from 170 volts to 270 volts to suit a harsh power supply environment. Fourth, the input power cord is preferably made of anti-high/low temperature, ultra-soft, and bend-resistant. There is a manufacturer of infrared light, the input power cord can be used at a temperature of minus 60 degrees Celsius, 250 degrees above zero at normal temperatures, minus four, fifty degrees of cable is still as soft as silk, this product is only worthy of trust.

The problem of angle

Infrared light is not the bigger the better? Whether manufacturers or contractors take it for granted, they believe that the greater the infrared light emission angle of view, the greater the scope for selecting the lens, and the selection of a wide-angle lens will not cause a "flashlight" phenomenon. So, everybody is desperate to say how big the perspective of their infrared light is. This seemingly reasonable argument is actually very unscientific.

First of all, there is a waste of light when using a large-angle infrared lamp with a small-angle lens. For example, with an infrared lamp, the light emission angle is 80 degrees (corresponding to the angle of the f3.5mm lens). If a lens with f35mm is used, a considerable part of the light will be outside the field of view of the lens, that is, part of the infrared light will be wasted. Under normal circumstances, the infrared light's viewing angle is consistent with the lens's viewing angle, and the effect is optimal. For example, the infrared lamp of Changchun Tatda, the light emission angle is represented by the focal length of the lens. Its SK-4.2W-16 infrared lamp, the meaning is this: "-4.2W" indicates that the lamp's rated power is 4.2 watts; "-16" indicates that the lamp's emission angle and the f16mm's lens angle are the same, both are Can be matched.

Its infrared lamps are classified by angle and currently include four series of "-4", "-8", "-16" and "-35", which can be matched with commonly used lenses on the market.

Second, the larger the angle of emission of the infrared light, the better the picture. In some cases, if the infrared light angle is too large, the imaging will be affected. For example, the corridor, because of its "narrow" characteristics, if the infrared light emission angle is too large, the imaging of the near edge will be too bright, forming a "light curtain" phenomenon; far away from the center but can not see, only a whitish phenomenon. Therefore, the infrared light in the corridor should be one-half or one-third of the camera angle.

Third, you can use "light up" technology, two narrow-angle infrared lights with the location and adjust the position, can achieve the effect of wide-angle lights, the market's "Nighthawk" series infrared night vision system, is the use of "receiving the light" Technology has achieved both long-term and wide-angle. Under the same power conditions, the "light up" technology can double the effect distance.

In general, the problem of the emission angle of the infrared lamp is both a selection problem and a technical problem. Lenses with different focal lengths should be selected in accordance with the infrared angle of the launch angle, infrared light emission angle under no circumstances should be greater than the lens angle of view, but in the narrow environment of the application, the choice should be smaller than the lens perspective Even one-third of the infrared light. Narrow-angle infrared lamps can achieve ideal wide-angle effects with a better effect and lower cost.

The amount of light

The relative aperture determines the light transmission capability of the lens. The relative light flux of the lens with an aperture of F1.0 is four times the light flux of the lens with a relative aperture of F2.0. The same camera, infrared light, respectively, with the above two lenses, infrared action distance can be doubled.

Large-aperture lenses are four to ten times better than conventional lenses in terms of infrared monitoring. It is reasonable to say that they should become necessary accessory products for infrared night-vision monitoring. However, due to high costs and technical difficulties, most infrared product manufacturers do not have the ability to supply.

As a result of well-known reasons, a large number of lenses on the market flooded with false-standard F-values, especially zoom lenses, only mark short focal lengths and non-standard telephotos, thus misleading the engineering firm, causing users to simply discern who is selling the genuine goods, and who Shoddy. Users are advised to go to a professional manufacturer to purchase the lens.

Focus offset problem

Due to different wavelengths of visible light and infrared light, the imaging focus is not on one plane, resulting in clear images under visible light conditions during the day, blurring under nighttime infrared light conditions, or clear images under nighttime infrared light conditions, and image blurring under daytime visible light conditions. It can be solved in three ways. First, the use of automatic focus integrated camera; second, the use of IR special focus does not shift the lens; third, the use of professional adjustment tools, under the existing lens conditions can also be achieved without offset.

Color problem

All black and white cameras are infrared-sensitive. Infrared light is a stray light for a color camera under visible light conditions, which will degrade the sharpness and color reproduction of the color camera. The filter of the color camera is to prevent infrared rays from participating in imaging. There are two ways to make the color camera sense infrared light. First, switch the filter to block the infrared light from entering under visible light; remove the filter under the condition of no visible light and let the infrared light enter. The image quality is good, but the cost is high and the switching mechanism will cause a certain failure rate. Second, opening a specific infrared channel on the filter allows infrared rays with the same wavelength as the IR lamp to come in. This method does not increase the cost, but the color reproduction is slightly worse.

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, an infrared night vision system within 50 meters is better if a camera with 0.1 lux is used; a night vision system with a range of 50 meters to 100 meters should use a camera with 0.01 lux; a night vision system with a distance of 100 meters or more should be 0.001 lux. Above the camera. Of course, as the sensitivity increases, the price of the camera will increase significantly.

Of course, like many other products, the phenomenon of camera imaginary indicators is particularly serious. I once took a 0.1 lux camera and a camera with a nominal 0.0001 lux for comparison. The latter was not as good as the former. More camera manufacturers artificially improve the signal strength, the sensitivity is very good, but the signal-to-noise ratio is very poor, resulting in a lot of night images "snow spots" a lot.

The problem of distance

One hundred people will have a standard infrared night vision distance for infrared products. I think it should be based on the effectiveness of the customer's application. What is the customer's standard? It is to see people! What "visual distance", "discovery distance", these uncertain statements are vague. The matching of cameras and lenses in different grades may cause the sensitivity of the light emitted by the same infrared lamp to be many times different, and the visual distance may also be much different. Therefore, it is unscientific to say how many meters a concrete infrared light is. A working distance of an infrared lamp can only be determined by matching the camera and lens of a certain quality. Also, because of the different environments in which the applications are applied, the effects will be very different and it is better to leave a certain margin.