Hi everyone,

I need a sensor to detect the proximity of the different colored fabrics I have. I have two options for taking measurements.

1- I can place the sensor in front of the fabric, but if a highly transparent fabric comes, the sensor's signal might pass through the fabric. 2- I can place the sensor next to the fabric, but the problem here is that the thickness of the fabric might be quite low, in which case only a part of the transmitter signal, not all of it, might hit the fabric. (for example, if the fabric is 5 mm and the transmitter laser's radius is 20 mm)"

So which sensor should you recommend, where should i put it (side of the fabric or in front of fabric)

 

We would need much more information. A detailed diagram or an annotated photo of the physical setup, for instance.

 

@BobTPH is right that you haven’t provided enough information. A description of the problem the sensor and associated apparatus is intended to solve will go a very long way in providing information about parameters and constraints that will make answer with anything but a guess much more likely.

Information about the sensor itself is vital (if it is a real constraint, that is, a required part of the device and not a choice made to early that has become a pivot point that may not allow success). Otherwise, information about what data the sensor is expected to produce, that is, what is “proximity” in this case, is also critical.

As far as guesses go, you see to be depending on a retroreflective sensor. Is that a requirement or could a sensor be placed on both sides of the sample? You might be able to increase detection reliability by using both reflection and transmission, possibly differentially.

By first calibrating the values for an empty detection field, which could be done repeatedly as long as it was a known empty field, you could use a differential approach between the face and reverse mounted sensors to increase detection confidence. But this is all just a guess, you need to describe the application and environment it is happening in for a sensible answer.