I am working on a project that detects the defects like holes, oil spills, knots etc in a given piece of cloth. I have installed an LED array on one side of the cloth while on the other side I want a light intensity sensitive detector. Which one -LDR (Light Dependent Resistor), Photodiode or Photo-transistor - should be used to detect small changes in intensity of light? I have checked the results with LDR (pull-up circuit) but it's own fluctuations are so much that I can hardly sense the changes due to the cloth.

 

Use phototransistor.
Modulate the LED by switching it on and off.

 

Thank You for the reply MrChips. Can you please elaborate your answer? I have also searched for different sensors and I myself came up with phototransistor. But what circuit should I use for phototransistor to get better sensitivity? What do you mean by modulating the LED?