3D microscopy has generally focused on rotating a specimen in front of a lens in order to digitize its volumetric structure. Now engineers at Ohio State have built an optical lens (see right image) that provides nine simultaneous viewing angles of an object at the same time. Pictured above is a view through the lens of a drill 0.2 mm in diameter. If this design is miniaturized further, scientists should be able to study live cellular interactions in a new way.
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. But while 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 [Allen Yi, professor of engineering] explained. Such a lens is called a “freeform lens,” a type of freeform optics.
Freeform optics have been in use for more than a decade. But Lei Li [Ohio State postdoc] was able to write a computer program to design a freeform lens capable of imaging microscopic objects.
Then Yi and Li used a commercially available milling tool with a diamond blade to cut the shape from a piece of the common thermoplastic material polymethyl methacrylate, a transparent plastic that is sometimes called acrylic glass. The machine shaved bits of plastic from the lens in increments of 10 nanometers, or 10 billionths of a meter – a distance about 5,000 times smaller than the diameter of a human hair.
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.
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.
Link: SEEING IN STEREO: ENGINEERS INVENT LENS FOR 3D MICROSCOPE…
Abstract in Journal of the Optical Society of America A: Design and fabrication of a freeform prism array for 3D microscopy