Almost all “premium version” of elevated body temperature detection system available in the market seems to have both visual and thermal camera in it. I think, main reason to put this visual camera is to identify the person without any human intervention in case he or she is detected with elevated body temperature. While, this argument may not hold true if she is wearing a mask or veil, but still it can give some desirable features to elevated body temperature measurement system
Both the Thermal Camera and the visual camera are places in such a way that their field of view ( FOV ) overlap each other so as to detect the face using visual camera while sensing the temperature using the thermal camera. The visual image will be used to detect a face, then this face area will be identified in the corresponding thermal image. Then the temperature of that area will be measured using the thermal camera.
While this sound pretty neat arrangement, but it may introduce few challenges too. For example :-
- Both thermal and camera have to be aligned such a way that they have maximum overlapping area.
- Aligning both camera may not be very easy if both the cameras are of different resolution and sensor size. Normally, thermal camera have lower resolution than the visual camera.
- The pitch size of the sensors of thermal and visual cameras also differ.
- The resolution of thermal camera should be much higher than the thermal camera.
- It may introduce a minimum working distance as they require overlap zone, unlike single thermal camera system which just have minimum focus distance.
This kind of dual camera system offers one advantage, that is automatic face recognition. Apart from that, I do not see any other advantage though. Auto face Recognition may help it become attendance system too. But then, RF ID based attendance system can blunt this advantage.
Personally, I will always prefer single camera system which has just the thermal camera or thermal sensors like LTE-384F, which is tripod mountable. As for attendance, I would use RF-ID based proximity card.
With visual camera, some people may have privacy issues too, specially if such system is installed in public places.
Having a visual camera is surely a nice feature as visual cameras are not very expensive. With visual camera, the elevated body temperature detection system becomes a complete solution with temperature detection, face recognition system.