Is it possible to use an IR sensor to differentiate accurately between carbon fiber and a human hand kept on the carbon fiber surface?

I would like to move the sensor from one end of the carbon fiber object (a rectangular surface) to the other and be able to detect a significant difference in reflected intensity when the sensor passes over the hand. Will this work? If not, what are alternative sensors that I could use? The sensor will be approximately 10 cm above the carbon fiber surface.


1 Answer 1


Some IR sensors just receive. In this case they distinguish only by difference in infrared emission from the environment. These sensors could not see a hand if it was inside an oven mitt for example or if the hand was the same temperature as the surface, but in most cases it would work.

In a photo gate setup you could have an IR led constantly on to illuminate the surface. It would work as long as the reflectiveity of your surface was always different from a hand (not sure if we are talking raw carbon fiber here or shiny epoxy coated carbon fiber). Dirt on a shiny surface would cause problems as would external heat sources like sunlight.

An infrared proximity sensor uses triangulation and will be able to distinguish your targets more reliably, but will still have sunlight issues. More info on IR sensors

You will want to look at an ultrasonic sensor. An ultrasonic sensor could easily handle the task and works better in dirty and sunny environments. A capacitive sensor would also work, but only at short range.

Sensor Examples:
Ultrasonic and infrared proximity sensors
Ultrasonic proximity sensors
Capacitive proximity sensor

  • $\begingroup$ Thanks for the answer. I was actually looking for a source which would help me 'calculate' or estimate the extent to which the two types of surfaces would reflect IR, but then realized the only real way to do it would be to try it out. Also, I was hoping to use the integrated IR emitter and sensor which we see in smartphones. $\endgroup$
    – Rustin
    Commented Nov 5, 2015 at 6:11

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