Scientists using a novel printing method have managed to make a color image whose resolution approaches the maximum theoretical limit. The Singapore team published their work in Nature Nanotechnology earlier this week.
Wired breaks down the science pretty well: the team created pixels using “nanoscale posts, with silver and gold nanodiscs on top.” How far apart these posts are, as well as their diameter, determines what color light they reflect. The pillars are all of a nanometer tall. The image’s resolution, in the end, is 100,000 DPI (dots per inch).
What is meant by a “maximum theoretical limit” to resolution? It turns out that the wavelength of light is such that if two objects are too near to one another, light reflecting off them will diffract. The result is a blurred image. For visible light, this happens when objects are 250 nanometers apart. That’s the same distance between pixels in the new nanoscale method. Said Chad Mirkin of Northwestern University to the BBC: this approaches “the limit of what is possible to print in color.”
How is this useful? Well, the team thinks they can commercialize the tech, and is going after a patent for it. Applications might include tiny watermarks –“ micro-images for security,” write the team members in their paper–or packing huge quantities of data onto a DVD. There are apparently also possibilities in cryptography.
The method the team used to produce color was a clever one, said Mirkin. Rather than using dyes or pigments, the team made “colors out of one material by adjusting nanostructure in a lithographic experiment.”
The last curious element of this story is the image the scientists chose to reproduce: an image of Lena Soderberg, a Swedish model who posed in 1972 for Playboy. This image (from the neck up, mind you) is actually canonical in computer imaging circles. It all started in 1973, when an imaging scientist at USC was looking for good image to scan for a conference paper. Reported Jamie Hutchinson in 2001: “They had tired of their stock of usual test images, dull stuff dating back to television standards work in the early 1960s. They wanted something glossy to ensure good output dynamic range, and they wanted a human face. Just then, somebody happened to walk in with a recent issue of Playboy.”
From that point on, use of the Lena picture in imaging circles grew, until it simply became standard. In 1997, Soderberg was a guest at the 50th annual conference of the Society for Imaging Science and Technology. She is known as the “first lady of the internet,” for the influence her image has had on digital imaging technologies. Since image compression essentially helped build the modern internet, the society’s president Jeff Seideman has said (NSFW), “The use of her photo is clearly one of the most important events in the history of electronic imaging.”