Sensor use to detect obstacle

I have found many papers on using a sensor skin (large numbers of IR
sensors) on a robot arm to detect an obstacle to avoid any collision.
I was wondering <b>whether it is possible to use minimal numbers of
sensors to do the same purpose</b>, i.e, measure the distance from the
robot arm to the obstacle which ultimately using the developed
software to compare it to a threshold value? If the measured distance
is less than the threshold, then collision is detected and the robot
would  be ordered to stop operation or change path.

Thanks