Novel Lens Simplifies 3-D Microscopy
COLUMBUS, Ohio, March 22, 2011 — A new lens designed by engineers at Ohio State University enables microscopic objects to be seen from nine angles simultaneously to create a 3-D image.
3-D imaging is typically achieved using multiple lenses or cameras that move around an object. The new device is the first single, stationary lens to create microscopic 3-D images by itself.
A lens invented at Ohio State University enables microscopes to capture 3-D images of tiny objects. (Image: Kevin Fitzsimons, OSU)
Associate professor Allen Yi and postdoctoral researcher Lei Li of OSU describe the lens in a recent issue of the Journal of the Optical Society of America A.
Yi 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. Although the engineers milled their prototype thermoplastic lens on a precision cutting machine, the same lens could be manufactured less expensively through traditional molding techniques, he said.
“Ultimately, we hope to help manufacturers reduce the number and sizes of equipment they need to miniaturize products,” he added.
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. And, although gemstones are cut for symmetry, this lens is not symmetric. The sizes and angles of the 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 said. Such lenses are a type of free-form optics. Free-form optics have been in use for more than a decade. But Lei Li was able to write a computer program to design a free-form lens capable of imaging microscopic objects.
Researchers at Ohio State University have invented a 3-D microscope lens that gathers images of tiny objects from nine angles at once. Here the lens captures a ballpoint pen tip that measures about 1 mm across. (Image: OSU)
Then Yi and Li used a commercially available milling tool with a diamond blade to cut the lens from a piece of PMMA (polymethyl methacrylate), shaving bits of plastic from the lens in increments of 10 nm. The final lens resembled a rhinestone, with a faceted top and a wide, flat bottom. The researchers installed the lens on a microscope with a camera looking down through the faceted side, and centered tiny objects beneath the flat side. 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 1 mm — and a mini drill bit with a diameter of 0.2 mm.
“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 microsamples instead of just a two-dimensional projection.”
Two Ohio State University engineers inspect a lens that enables microscopes to capture 3-D images. Shown from left to right are inventors Lei Li and Allen Yi. (Image: Kevin Fitzsimons, OSU)
In the future, Yi would like to develop the technology for manufacturers. He pointed to the medical testing industry, which is working to shrink devices that analyze fluid samples. Cutting tiny reservoirs and channels in plastic requires a clear view, and the depths must be carved with precision.
Computer-controlled machines — rather than humans — do the carving, and Yi said that the new lens can be placed in front of equipment that is already in use. It also can simplify the design of future machine vision equipment because multiple lenses or moving cameras no longer would be necessary.
For more information, visit: www.osu.edu
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