That patent only seems to cover using the same camera for both sign recognition and forward collision detection by switching between two different sets of image

That patent only seems to cover using the same camera for both sign recognition and forward collision detection by switching between two different sets of image capture parameters and then dividing the frames captured between the two different algorithms. It's not a general patent on sign recognition. Tesla have enough cameras on their current cars, and camera technology has improved by enough over the years, that I can't imagine that being necessary.