Airports in New York and Los Angeles have become the latest equipped with body scanners that allow security screeners to peer beneath a passenger’s clothing to detect concealed weapons.

The machines, which are about the size of a revolving door, use low-energy electromagnetic waves to produce a computerized image of a traveler’s entire body. Passengers step in and lift their arms. The scans only take a minute, and Transportation Security Administration officials say the procedure is less invasive than a physical frisk for knives, bombs, or guns.

Someday, the “millimeter wave” scans might replace metal detectors, but for now they are being used selectively.

John F. Kennedy International Airport and Los Angeles International Airport saw their first scanners installed yesterday, each at a single checkpoint. Phoenix Sky-Harbor International Airport got one of the machines in October.

Modest travelers may have concerns about the images.

The black and white, three-dimensional scans aren’t as vivid as a photograph, but they do reveal some of the more intimate curves of the human form, maybe with as much clarity as an impressionist sculpture by Auguste Rodin.