New Lens Can See Tiny Objects in 3-D
A new lens can resolve tiny objects in 3-D, such as the tip of a ballpoint pen in this image.
CREDIT: Ohio State University
Engineers have invented a lens that enables microscopic objects to be seen from nine different angles at once to create a 3-D image.
Other 3-D microscopes use multiple lenses or cameras that move around an object, whereas the new lens is the first single, stationary lens to create microscopic 3-D images by itself, according to its makers.
Researchers called the lens a proof of concept for manufacturers of microelectronics and medical devices , who currently use very complex machinery to view the tiny components that they assemble.
"Ultimately, we hope to help manufacturers reduce the number and sizes of equipment they need to miniaturize products," Allen Yi, associate professor of integrated systems engineering at Ohio State University, said in a statement. Yi is co-author of a paper in a recent issue of the Journal of the Optical Society of America A.
The prototype lens, which is about the size of a fingernail, looks at first glance like a gem cut for a ring, with a flat top surrounded by eight facets. Although gemstones are cut for symmetry, this lens is asymmetric – the sizes and angles of its facets vary in minute ways that are hard to see with the naked eye.
"No matter which direction you look at this lens, you see a different shape," Yi explained.
Such a lens is called a "freeform lens," a type of freeform optics that has been in use for more than a decade.
Making the lens
Paper co-author Lei Li, also of Ohio State, wrote a new computer program to design a freeform lens capable of imaging microscopic objects.
Then the researchers used a commercially available milling tool with a diamond blade to cut the desired lens shape from a piece of the common thermoplastic material polymethyl methacrylate, a transparent plastic that is sometimes called acrylic glass.
The final lens resembled a rhinestone, with a faceted top and a wide, flat bottom. They installed the lens on a microscope with a camera looking down through the faceted side and centered tiny objects beneath the flat side.
Seeing in three dimensions
Each facet captured an image of the objects from a different angle, which can be combined on a computer into a 3-D image .
The engineers successfully recorded 3-D images of the tip of a ballpoint pen – which has a diameter of about one millimeter – and a miniature drill bit with a diameter of 0.2 millimeters.
"Using our lens is basically like putting several microscopes into one microscope," Li said. "For us, the most attractive part of this project is we will be able to see the real shape of micro-samples instead of just a two-dimensional projection."