US Patent 8669876 Above-water monitoring of swimming pools

An above-water system provides automatic alerting for possible drowning victims in swimming pools or the like. One or more electro-optical sensors are placed above the pool surface. Sequences of images are digitized and analyzed electronically to determine whether there are humans within the image, and whether such humans are moving in a manner that would suggest drowning. Effects due to glint, refraction, and variations in light, are offset automatically by the system. If a potential drowning incident is detected, the system produces an alarm sound, and/or a warning display, so that an operator can determine whether action must be taken.