Invisible watermarks can help protect intellectual property rights.

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Protecting intellectual property rights is very important to artists and businesses alike. Because the ways in which we experience media keep changing, companies that produce and own that media are constantly trying to keep up and ensure that they still own and profit from their property.

One relatively unobtrusive method of protecting digital images is the watermark, which people have been using in some form or another for quite some time. The classic watermark appears on an image, protecting creators from having their images used illegally.

The problem with a watermark, however, is that it can be cropped out unless it’s placed right across the middle of an image, as some stock photo sites do. Most creators don’t want to do that because of the negative effect it has on the image itself.

A team of researchers at the University of Chinese Academy of Sciences (UCAS) in China has solved the conundrum of protecting creative works while still preserving aesthetic value: they have developed a system of invisible watermarks.

“In our research, we use a complex pattern of light, or diffraction pattern, as a unique watermark,” says Yishi Shi of the UCAS. “The invisible watermark is embedded into the content we are trying to protect. Imperceptibility is one of the most significant advantages of optical watermarking.

The method starts with a technique called single-shot ptychography encoding (SPE), which uses multiple partially overlapping beams of light to generate a unique diffraction pattern. The watermark can be encoded without mechanical scanning, which makes it less expensive and easier to do than other digital watermarking methods.

While invisible watermarks might seem to defeat the purpose of watermarking, it actually does not. This technology could be especially useful for photographers, who want to sell their work to consumers but don’t want that work to be reproduced without their permission. With an invisible watermark, a consumer could buy or download a digital print for personal use, but it would prevent the image from being used illegally because the creator could prove ownership.