Collision avoidance sensors for UAVs

Hello, What would be the best sensors to use for a collision avoidance system on an UAV. From my research a multi sensor system is a good idea since all sensors have certain limitations. What combination would you suggest (IR and ultrasonic or US and LIDAR... etc)?

Ultrasonic is probably the cheapest option, since the range is up to 7 meters. But make sure you buy the expensive one. Ultrasonic sensors for 5$ can be messed up with vibration and can therefore read false values. IR sensors are not made for distances higher than 1m (as far as I know) so you can't really use them. Probably the best bet is LIDAR or camera with computer vision.