I need a sensor capable of detecting and counting any kind of seed, including smaller ones like canola seeds which are in the range of 1mm of diameter. The seeds will be falling through a tube, and the sensor should be at the bottom of it. I dont know if normal IR sensors have beams that are narrower than 1mm, or if there is any way in which I could adapt the receiver so that it could detect such small seed.
If there is any other kind of sensor capable of this that I am missing, let me know. Also it si very important that the trajectory of the seed ramains untouched after detecting it.