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X-Ray Specs are an American novelty item, purported to allow the user to see through or into solid objects. In reality the glasses 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.
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 6 mm (.25 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, supposedly giving the illusion that one is seeing the graphite embedded within the body of the pencil. As may be imagined, the illusion is not particularly sustainable.
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, of course; besides the unlikelihood of a safe and functional X-ray device selling for about a dollar, X-ray detectors require an X-ray source.
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.
The principle behind the illusion, as well as its use in a pair of "spectacles", was first patented (in the United States) in 1906 by George W Macdonald (Patent# US839016). 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 (Patent #914904)
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 UK punk band The X-Ray Spex.