3D imaging tech touts super-high resolution

Researchers in MIT's department of brain and cognitive sciences have designed a simple, portable 3D imaging technology that touts super-high resolutions and can provide manufacturers with a way to inspect products too large to fit under a microscope. The system can be used in medicine, forensics and biometrics, the researchers say.

The team of researchers that is responsible for the 3D imaging system include Edward Adelson and Micah Kimo Johnson, along with graduate student Alvin Raj and postdoc Forrester Cole.

The core of the system, dubbed as GelSight, is a slab of transparent synthetic rubber, in which one side is coated with paint containing tiny flecks of metal.

GelSight can register physical features less than a micrometer in depth and about two micrometers across. When pressed against the surface of an object, the paint-coated side of the slab deforms. Cameras mounted on the other side of the slab photograph the results and computer-vision algorithms analyze the images. Because GelSight uses multiple cameras to measure the rubber's deformation, it can produce 3D models of an object that can be manipulated on a computer screen for examination from multiple angles.

Adelson and Johnson have built a prototype sensor—about the size of a soda can—that an operator can hold in one hand and can produce 3D images almost instantly. They are now in discussion with one major aerospace company and several manufacturers of industrial equipment that are interested in using GelSight to check the integrity of their products.

Although GelSight's design is simple, it addresses a fundamental difficulty in 3D sensing.

Johnson illustrated the problem with a magnified photograph of an emery board, whose surface, in close-up, looks a lot like marmalade—a seemingly gelatinous combination of reds and oranges. "The optical property of the material is making it very complicated to see the surface structure," Johnson noted. "The light is interacting with the material. It's going through it, because the crystals are transparent, but it's also reflecting off of it."

When a surface is pressed into the GelSight gel, however, the metallic paint conforms to its shape. This results in uniform optical properties of the surface. "Now, the surface structure is more readily visible, but it's also measurable using some fairly standard computer-vision techniques," Johnson added.

"We need the pigments to be smaller than the features we want to measure," Johnson explained. However, the different reflective properties of the new pigments required the use of a different lighting scheme and that in turn required a redesign of the computer-vision algorithm that measures surface features.