Imaging Through Haze

SWIR Imaging Penetrates through Haze for Port and Homeland Security and Surveillance

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 short wave 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).

This is especially important in both port and harbor security scenarios where fog and haze are a regular occurrence. Short wave 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.

This video shows how a Sensors Unlimited SWIR camera penetrates through haze to reveal Berkely city landscape.

This video shows the superior performance of SWIR cameras penetrating through fog and haze of the San Francisco Bay Bridge.

The short wave 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 SWIR camera detects the reflected light, not the temperature - making the human body stand out.

In the image below, the left side demonstrates how a short wave infrared camera can detect warm human bodies in water regardless of its temperature. The image on the right shows that a thermal camera will have difficulty imaging a warm human body in warm water, which is called thermal crossover.

In the image below, note how the shoreline below stands out, and captures more detail than a visible camera.

(Point Loma, CA at sunrise. Goodrich SWIR cameras provide effective imaging day and night thus eliminating thermal crossover.)

As an added benefit, Sensors Unlimited cameras require no cooling and can image day or night, eliminating the costly need to change a camera for day and night use. In order to serve a variety of security platforms, SWIR technology is rapidly advancing with better performance being offered in smaller packages.