..Laser rangefinder built-in to the pilot's head? ...Phew!
From the Airprox report with my emphasis added:
"The pilot established visual contact, he estimated 100m away but it was very difficult to tell, as he manoeuvred the ac to avoid a collision and to identify the light source."
Have you never felt the wash from a helicopter taking off or landing? I have, and it extends a considerable distance.
Joe