no need to worry!!! you see some weird cut markings in the road when you approach a road signal.If you haven't observed next time watch for it. they are conductors which emmit magnetic waves. if at all you disturb the magnetic waves at a certain speed then only the camera gets activated (when the red light is on).in your case nothing to worry. Even when it is red for the first 1/2 second the camera will not flash. (but dont take a chance:).

so dont you worry! drive safe and reach safe...