Unfortunately I won't be able to put any marks on the cylinder, and in some cases they will be black, meaning very low reflectivity in a dark room, making motion detection that much harder. It would be possible, however, to have a white LED light the area the sensor will be measuring.
I don't have any cylinder photos. The sensor has to work on a range of cylinders on various machines. Generally the cylinders will be 8-15" in diameter, 2-10" high and will spin at 20-100 rpm. Materials will be various metals, typically aluminum or steel, and plastics such as acrylic or polycarbonate, and possible others.
My guess is it will be easy to detect motion when there are surface imperfections. I'm more concerned about exceptionally smooth surfaces that to the human eye might almost appear to not be moving at all if the cylinder's spinning fast enough, which I guess comes down to sensor sensitivity, and I don't have a good handle on that.
Most of what I've read about sensors points to infrared, which is what I'm most familiar with and will probably use for another aspect of this devise that detects motion of a part moving linearly past a fixed sensor at a similarly close range. This is what I had in mind:
GP2Y0D810Z0F Sharp Microelectronics Industrial Optical Sensors
But they call this a "distance measuring" sensor. With the cylinder at a fixed distance the distance to measure isn't changing. However, if there are surface imperfections those could minimally change the distance if the sensor's sensitive enough to detect them. And I guess the same could be said about a surface that visually appears to be very smooth. If you magnify a seemingly smooth surface enough there are imperfections.
Do you think an IR sensor the right choice? Is this one in particular going to be sensitive enough or should I look elsewhere?