Which is it: Millimeter Wave or Backscatter?

As TSA continues to deploy new technology, some people continue to be confused about whole body imagers. Millimeter wave, backscatter, privacy filters… it all adds up to a confused traveling public.

Since one of our readers asked about the difference between millimeter wave and backscatter images in a previous post and we’ve also seen other blogs get the two confused, we thought we’d put the correct information and images out there to clear up any misinformation. Both millimeter wave and backscatter fall under the classification of whole body imaging, which gives security officers a virtual image of a passenger that highlights potentially dangerous items.

Here’s the lowdown on the two technologies:

How millimeter wave works:

Beams of radio frequency (RF) energy in the millimeter wave spectrum are projected over the body’s surface at high speed from two antennas simultaneously as they rotate around the body.


The RF energy reflected back from the body or other objects on the body is used to construct a three-dimensional image.

The three-dimensional image of the body, with facial features blurred for privacy, is displayed on a remote monitor for analysis. The image is not saved – once it’s off the screen it’s gone forever.

This is the millimeter wave image a security officer sees:

A millimeter wave machine looks like this:

Here’s how Millimeter Wave imaging works (WMV, 3.4 MB).

Here’s how Millimeter Wave technology detects threats (WMV, 3.4 MB).

How backscatter works:

A narrow, low intensity X-ray beam is scanned over the body's surface at high speed.
The technology relies on the X-ray radiation that is reflected back from the body and other objects placed or carried on the body, where it is converted into a computer image, embedded with a modesty filter and displayed on a remote monitor.

Passengers will walk up to the backscatter unit, assisted by a transportation security officer and remain still for several seconds while the technology creates an image of the body.
Images will be deleted immediately once viewed and will never be stored, transmitted or printed (the passenger imaging units have zero storage capability).

This is the backscatter image the security officer sees:




This is a backscatter machine.

Click here to see a demonstration of backscatter (2Mb, wmv).

And while we’re at it:

Because we see it time and time again, we wanted to clear up another bit of misinformation. This is a raw backscatter image with NO privacy algorithm. This is NOT what security officers see – this image was used to show what the capabilities of the technology are.