Low-Light Cameras (Part I)

Low-Light Cameras (Part I)
Industry sources all agree that sufficient lighting is the best crime deterrent, but it is often not available where one needs it. As conventional surveillance cameras are not equipped with the required sensitivity to see in near or total darkness, there is always a need for add-on tools like infrared illuminators.

The question of how best to cover a dimly lit or totally dark area with an affordable video solution is a common one. According to Jon Chynoweth, Executive Vice President of Sales and Marketing for Cantronic Systems, the worldwide market for low-lux/ low-light cameras is valued at approximately US$300 million. These camera systems are generally used at large premises and/or remote places, such as border controls and ports of entry, perimeter protection for high-profile areas, and critical infrastructure and chemical plants. One thing to keep in mind is that there are two approaches to solving the problem of seeing at night one through supplementary illumination and the other proprietary sensor engineering and each has its virtues.

Infrared (IR) illumination is a good fit for places with virtually no light that only need coverage in a limited or confined area. An analogy can be made: Using an IR camera is like walking in pitch black with a flashlight; the smaller the flashlight, the smaller the visible area.

While IR cameras attempt to make their picture more useful by supplying their own light source, low-light cameras take the opposite approach and attempt to take advantage of any ambient light available, including natural sources such as the moon and stars. There is also viable, mature technology that does not require any light. All of them, of course, depend on advanced R&D of optics and sensors.

Proprietary Sensor Engineering

There are a couple of ways to boost low-light performance. The method used affects overall picture quality. Generally speaking, a camera with superior optics gives users a truer reproduction than one that relies on electronics. The goal of superior optics is to deliver as much light as possible to CCD or CMOS image sensors.

Another factor to consider is the number of image sensors or chips that a camera uses. All other things being equal, multiple chips are always better than one, said Sungje Jo, Sales Director for Three Brain Technology (TBT). "For example, our dual-CCD camera has one high-quality lens and two CCDs, color and black-and-white. The two CCDs are interchangeable, depending on light conditions. This is different from other cameras which have two lenses and two CCDs dual-lens cameras have the disadvantage of having different fields of view during the day and at night."

Single-chip cameras do have the ability to see with very little light and at a more affordable price. When there is not enough light, the camera takes what light it does have and amplifies it electronically. The resulting picture, however, is less than perfect as amplification of a low-light signal inevitably results in graininess and video noise.

On the other hand, there are people who are working toward solving these drawbacks. A new, revolutionary, single-chip CMOS image sensor technology developed by NoblePeak Vision solves the complexity and cost problems associated with prior sensing technology. "Using this single chip, TriWave technology enables security and surveillance video cameras to see in the harshest zero-light conditions, surpassing the capabilities of even the most sensitive low-light cameras on the market," said Phil Davies, Vice President of Sales and Marketing at NoblePeak Vision.

The breakthrough is that NoblePeak has found a way to significantly enhance the wavelength response of a standard CMOS image sensor through the addition of germanium to the CMOS process. Germanium is an element that is sensitive to short-wave IR (SWIR), and its longer wavelength sensitivities able to detect the "night glow" are due to its smaller band gap properties.

Additional advantages of the CMOS process are that it allows for small pixel sizes and higher resolution imagers, resulting in smaller/lower optics, camera system size, weight and cost. "Another advantage of TriWave is that it is sensitive across three bands of the electromagnetic spectrum: visible, near IR and SWIR," explained Davies. Therefore, TriWave cameras can function both day and at night, eliminating the need for separate cameras.

More Information
Low Light Cameras (Part II)

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