The first thing I would check is the drivers for it. You may want to try uninstalling them, reboot the system and then (if they don't auto reinstall on their own) manually reinstall them. Also, once they have been reinstalled, make sure that it is the most up to date version of the driver.
Clean the webcam. Dust, finger prints, liquid, etc., could have gotten on the lens. Try a cotton swab and some lens cleaner and carefully clean it off. You can use the other end of the cotton swab to dry it faster.
Should this continue to be a problem still, check to see if the problem occurs all the time, or only when running certain programs at the same time. If resources are low, this can effect it. You may also want to try running the computer in "Safe Mode" to see if the problem persists in there.
If nothing else has helped, then it may be time for professional help. If under warranty, I would contact the manufacturer about a repair or replacement.