Developed for the U.S. military, the AN/PVS-4 is a night vision gunsight for personal weapons such as the M16 rifle, M4 carbine, and machine guns. It attaches to any weapon equipped with the mounting mechanism of the Picatinny rail system.
It also can be detached and used as a handheld night vision device, for tasks such as maintenance and first aid.
The device is "second generation", meaning it amplifies available light rather than sensing the thermal radiation of an object. Its approximate range of detection, for a human-sized target, is 400 yards/357 meters by starlight and 600 yards/548 meters by starlight.