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Jan 10, 2020 | 10:13 am 930 0

How do night vision cameras work?


How do night vision cameras work?

Security cameras have come a long way since their first introduction into the market. Currently most security cameras come with a night vision mode, allowing them to see and capture footage in total darkness. We will discuss how these current night vision security camera’s work and the varying technologies utilized to capture and record in the dark.

How does night vision security camera work?

There are different types of night vision currently used and available within the market. These are not generational differences (i.e. Gen1, Gen2, Gen3) but technological differences such as Digital and Analog. All of these technologies are readily used and available in the security, hunting and camera markets. Most security cameras are using a digital system, as this is comprised of an internalized chip and sensor. Like most cameras you have the ability for a digital zoom enhancement. These digital systems can operate in both day and night, as there is no risk in damaging internalized components due to light exposure. Just like cameras, phones or recorders you can turn up or down the gain (sensitivity to light) control. On the other end of the night vision market you have analog night vision. These devices are typically used in night vision monoculars, goggles or weapons sights, and are further evaluated by their Generational grade (Gen1, Gen2, Gen3). The main variance between the digital and analog system, is that analog uses magnified lenses (much like a traditional rifle scope) but with a photocathode image intensifier tube in the center of the magnified glass. These tubes gather all available ambient light, radiating a green image (green phosphorus tubes) or white/black (white phosphorus tubes) of the object or subject your viewing. 

Infrared Night Vision

Security cameras are utilizing infrared night vision, which relies on infrared light to function. This infrared (IR) light is completely invisible to the naked eye. Think of your current TV remote, which has a red LED at the front of the device and sends an infrared signal to your television. You cannot see this beam transmitting to your TV as it is in the infrared focal plane. The same can be said about IR illuminators and IR lights. These devices are typically mounted on the camera itself and shine a spotlight of infrared light, allowing these devices to capture images/video and view in total darkness. Most security cameras now come with built-in infrared LEDs to provide night vision in low light or no light condition.

Several security cameras that offer night vision capabilities, will also includie an IR cut filter. An IR cut filter is a mechanical shutter, placed between the lens of the camera and the image sensor. This filter will automatically detect ambient light (sunlight, visible light) and applies a filter to block out the IR light during the day in order to keep the image and clarity of the daylight. The infrared cut filter is being controlled by a light sensor on the security camera, and at twilight, the light sensor simply sends a remove signal to the infrared cut filter so that more light could reach the image sensor of the security camera. This allows more light in, including the IR light coming from the camera itself. Typically, all digital infrared cameras will show black/white image in night vision mode, and not the green hue popularized by the colored phosphorus of analog night vision systems.

Low-Light Night Vision

Low-light night vision relies on image intensification technology (analog) to deliver a colored night vision image in a very low light atmosphere. When ambient light strikes a charged photocathode plate, electrons are emitted through a vacuum tube that strike the microchannel plate, causing the image screen to illuminate with a picture in the same pattern as the light that strikes the photocathode, and is on a frequency that the human eye can see. Analog systems will show the picture in either a green hue or white/black image, dependent upon the image intensifier tube utilized (green or white phosphorus). Because this technology is utilizing optical viewing, as opposed to a digital enhancer, the clarity and resolution of analog devices are typically much clearer than digital units. One area to note, is because of the light sensitivity tube, you must have an IR cut filter, or additional precaution to limit light exposure during the day. There is possibility in damaging the internal intensifier tube when exposed to too much ambient / visible light (sunlight, car headlights, flood lights).

Conclusion

There are several key technologies in the advancement of security cameras. Primarily the advancement of digital and analog components that allow for day/night operation of night vision cameras. Due to variances in technology, it is important to point out that Digital night vision is going to be the cheapest and most budget friendly device mentioned above, whereas analog night vision is going to provide a higher price point, due to the costs involving the image intensifier tubes and overall higher clarity and resolution. As technology continues to expand, and devices become more compact and cheaper to the overall market, the trend of more powerful, technological and capable devices will become much more prevalent throughout the market.

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