Police say new night-vision goggles for the crew of their helicopter Eagle have already proven a success, playing a major role in finding missing trampers.

A group of missing trampers was recently destined to spend a cold night in the bush, out of cellphone range, but their phone screens "showed up like a lighthouse" with the new goggles, Senior Constable Al Grant said.

The helmet-mounted goggles amplify light up to 3000 times. Police say Eagle's infra-red system is still its primary night-time detection and surveillance tool but the goggles have increased the Auckland-based crew's ability over rural terrain in the dark.