Thermal optical camera systems combine the best of both technologies. Instead of purchasing thermal and optical cameras separately, a combined system enables users to monitor areas regardless the time of the day or environmental conditions.
Thermal optical camera systems combine the best of both technologies. Instead of purchasing thermal and optical cameras separately, a combined system enables users to monitor areas regardless the time of the day or environmental conditions.
That was a point brought up in a recent
technology note by
Kintronics.
In the world of video surveillance, both optical (or visible) cameras and thermal cameras are employed, each with its unique features and applications.
“Optical IP cameras are primarily used for general surveillance. We use IP camera systems indoors and outdoors to view and record everything from criminals to wildlife,” the article said. “Thermal IP cameras are excellent for nighttime surveillance and can also be used to provide non-contact temperature measurements. The thermal imaging camera not only can be used at night, it can also ‘see’ through rain, snow and fog so can be used to enhance surveillance applications.”
Putting the two together in one system can be beneficial for users, the note said. “By combining the optical and thermal cameras, we create a very effective long-range camera surveillance system. Since the cameras are mounted together on the same pan-tilt mechanism, the system is effective for the detection, recognition and identification of the target. The dual IP camera systems are also good for viewing objects that are many kilometers away,” it said.
Components used
According to the note, the following are components used in an optical-thermal long-range system to achieve optimal results.
Sensor
The optical sensor used in a long-range camera system provides megapixel resolution and can operate in low-light. “There is a trade-off between resolution and low-light sensitivity. 2-megapixel optical cameras have the best low-light sensitivity, while the latest 4K cameras (12-megapixel) provide the widest field of view but less low-light sensitivity,” the note said.
The thermal camera uses a special sensor that views the infrared spectrum of the electromagnetic spectrum. “Thermal sensors with a resolution of 640 x 480 pixels are the most popular but are also available with lower and higher resolution. The price of the thermal camera depends on the resolution of the imaging systems. The higher the resolution the wider the field of view and the easier it is to spot the target. Even though they provide lower resolution than the optical camera, the thermal camera can detect an object at a greater distance than the optical camera. This is because the object will bloom brightly if its temperature is hotter than the surrounding area,” the note said.
Lens
The optical camera uses a special long-range zoom lens. One of the systems cited by the note uses a lens that zooms from 32mm to 2050mm. “The higher the mm number the further you can see. For example, a 140 mm lens provides enough magnification so that you can tell if a person is carrying a rifle at a range of about half a mile (829m) away. If the camera uses a 500mm lens, you can see the person over 1.5 miles (2,500m) away.”
The thermal camera, on the other hand, uses a special germanium lens that can pass the infrared spectrum. “There are fixed lenses, and variable zoom lenses available. For example, we can select a wide lens to view a border crossing, or a narrow lens to view a road. Fixed lenses vary from 50 mm to over 100 mm, and there are variable lenses that zoom from 34 mm to 155 mm,” the note said.
Pan-tilt
According to the note, the pan-tilt mechanism needs to be very stable. “The further away you try to see, the more small movements disturb the video. The high-performance pan-tilt mechanisms moves the camera by 0.01 degrees,” it said. “The pan-tilt mechanism gets more expensive as the viewing distance increases. This is because it needs to move a heavier camera lens assembly. Pricing also increases when the pan-tilt mechanism needs to move quickly to track fast-moving objects.”
Laser illumination
The laser illuminator can provide focused IR light up to 5 kilometers away, the note said, adding that the better-quality laser illuminators adjust the focus angle so that it maximizes the light depending on the focal distance of the optical zoom lens. “This reduces hot spots that can affect the video quality,” it said.