X-ray specs are American novelties, purported to allow users to see through or into solid objects. In reality, the spectacles merely create an optical illusion; no X-rays are involved. The current paper version is sold under the name "X-Ray Spex"; a similar product is sold under the name "X-Ray Gogs".
Description
X-Ray Specs consist of an outsized pair of glasses with plastic frames and white cardboard "lenses" printed with concentric red circles, and emblazoned with the legend "X-RAY VISION". The "lenses" consist of two layers of cardboard with a small hole about a quarter-inch in diameter punched through both layers. The user views objects through the holes. A feather is embedded between the layers of each lens. The vanes of the feathers are so close together that light is diffracted, causing the user to receive two slightly offset images. For instance, if viewing a pencil, one would see two offset images of the pencil. Where the images overlap, a darker image is obtained, giving the illusion that one is seeing the graphite embedded within the body of the pencil. Newer versions utilize manufactured diffraction lenses instead of feathers.
Value
X-Ray Specs were long advertised with the slogan "See the bones in your hand, see through clothes!" Some versions of the advertisement featured an illustration of a young man using the X-Ray Specs to examine the bones in his hand while a voluptuous woman stood in the background, as though awaiting her turn to be "X-rayed". The claim is untrue. Advertisements and packaging usually state that X-Ray Specs operate by "illusion", often in smaller print below the X-ray claims. Part or even most of the novelty value lies in provoking the object of the wearer's attentions. These subjects, if unable to be entirely sure that the device did not indeed allow the wearer to compromise their modesty, were liable to respond with a variety of amusing reactions. Indeed, instructions with the packaging explain how to provoke reactions, how to "CONVINCE the gals that your X-Ray Spex are for real!"
History
The principle behind the illusion, as well as its use in a pair of "spectacles", was first patented in 1906 by George W. Macdonald. A tubular configuration employing the same principle as well as the use of a feather for the diffraction grating was first patented in 1909 by Fred J. Wiedenbeck X-Ray Specs were improved by Harold von Braunhut, also the inventor of Amazing Sea-Monkeys. A previous product called the Wonder Tube worked in a similar way. Instead of glasses, the device was in the form of a small telescope. Their name was used as the inspiration for the UKpunk band X-Ray Spex.
Similar useful devices
Thermal imaging goggles are used by various military and police organizations. They are intended for night use, but the longer wavelength of infrared light allows the user to see images through some materials that are impervious to visible light. Some video cameras have a night mode that gives an IR image under the right conditions. Digital cameras can also be used.
Devices for airport security are able to see through clothing quite well. Some of these are true X-ray devices, using backscatter X-rays. The devices are not portable and use a typical X-ray display screen, not goggles.
