[petek]

Have you taken a look at what the camera is seeing when it's close to the rack (with LabView)? You may find that the light appears as a very thin line of pixels, with a low tracking confidence value. If you have filtering set above 0 (and therefore subtracts pixels), when the camera is very close to the rack the light may "disappear". If that is the case, you may get better results with filtering set to 0, or by placing the camera farther back and/or higher on the robot to give it a better viewing angle.