Have you ever wondered how the security scanners at airports work?

How do they detect hidden objects under your clothes without exposing you to harmful radiation?

The answer is millimeter wave technology, a form of electromagnetic radiation that can penetrate clothing and reflect off the body. In this post, I will explain the basic principles, components, usage, pros and cons of this technology.

Millimeter wave scanners are whole-body imaging devices that use two rotating antennas to emit and receive millimeter waves, which have wavelengths between 1 and 10 millimeters.

The antennas scan the body from head to toe and create a three-dimensional image based on the reflected waves.

The image is then displayed on a remote monitor for analysis by a security officer.

The whole process takes only a few seconds and does not require the person to remove any clothing or accessories. The main components of a millimeter wave scanner are:

  • A transmitter that generates millimeter waves using a solid-state device called a Gunn diode or a vacuum tube device called a backward wave oscillator.
  • A receiver that detects the reflected waves using a device called a Schottky diode or a heterodyne
  • A signal processor that converts the analog signals into digital signals and performs image
    reconstruction algorithms.
  • A display that shows the image on a screen or a monitor.

The main advantages of millimeter wave scanners are:

  • They are safe for humans, as millimeter waves are non-ionizing radiation that do not damage DNA or cause cancer.
  • They are effective for detecting metallic and non-metallic objects, such as explosives, weapons, drugs, or liquids.
  • They are fast and convenient, as they do not require physical contact or removal of clothing.

The main disadvantages of millimeter wave scanners are:

  • They are expensive to operate and maintain, as they require high power consumption and frequent calibration.
  • They are invasive of privacy, as they reveal the shape and contours of the body, which may cause discomfort or embarrassment for some people.
  • They are not foolproof, as they may miss some objects that are concealed in body cavities or covered by thick clothing.

Millimeter wave scanners are one of the common technologies of full body scanners used for security screening at airports and other venues. They were first developed at the Pacific Northwest National Laboratory (PNNL) in the 1990s and commercialized by L3 Communications (now Leidos) in the 2000s. They have been deployed in hundreds of airports around the world and have been proven to be effective in preventing terrorist attacks and smuggling activities.