The photocathode of an image intensifier can be used as an ultra-fast shutter. By varying the voltage on the photocathode, the image intensifier gate can be switched between open and closed. When the gate is open, incoming photons can enter the image intensifier and the light intensity is boosted. When the gate is closed, incoming photons can’t enter the image intensifier.

Switching the gate between open and closed states can be done very quickly, thus allowing the gate to be opened for a very brief moment. This enables effective exposure times in the order of nanoseconds.

By opening the image intensifier gate only once during each exposure of the camera sensor, you can eliminate motion blur even when imaging fast-moving objects. The video below illustrates the effects of image intensifier gating.

The first part of the video shows a bullet recorded at 15000 fps. Despite the high frame rate, the bullet moves so fast that it is blurry. The second part of the video shows the benefits of image intensifier gating. By opening the image intensifier for just 2 microseconds during each frame of the camera, the bullet is no longer blurry. It is perfectly sharp in each frame of the video.