InGaAs SWIR imagers are complimentary to thermal imagers when it comes to vision enhancement and low visibility in poor weather conditions. Imagery in the SWIR is similar to visible imagery, in that it senses reflected light, thus interpretation and scene analysis is improved over thermal systems. Thermal imagers have good detection abilities, and such imagers are a good compliment to the shortwave infrared. While thermal imaging can detect the presence of a warm object against a cool background, a SWIR camera can actually identify what that object is (for example, ships, vehicles, and personnel).
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An I2CCD camera surveying a ship in a harbor. |
Surveying the same ship, the shortwave IR image is clearer, highlighting ship details. |
This is especially important in both port and harbor security scenarios where fog and haze are a regular occurance. Shortwave infrared cameras can help with the detection and identification of floating objects or approaching ships. That's because thermal imagers do not provide the resolution and dynamic range of imaging possible with an InGaAs SWIR focal plane array.
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A clear advantage of shortwave IR cameras is that they can penetrate through fog and haze in order to provide more information-rich imagery. Left, a landscape taken with a visible camera. Right, the same landscape taken with a SUI camera. |
The shortwave infrared can also aid in thermal cross over scenarios. Thermal crossover is simply a point where the temperature of the object you are trying to image is equivalent to the temperature of the background. For example, a human in warm water is difficult to detect with a thermal imager, as shown in the images below. At this point, a shortwave IR camera detects the reflected light, not the temperature - making the human body stand out.
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A shortwave infrared camera can detect warm human bodies in water regardless of its temperature. |
A thermal camera will have difficulty imaging a warm human body in warm water, which is called thermal crossover. |
As an added benefit, SUI cameras require no cooling and can image through standard glass optics. Being able to see through plain glass eliminates the need for costly lenses and optics. In order to serve a variety of security platforms, SWIR technology is rapidly advancing with better performance being offered in smaller packages.