Holography offers a way of creating complete 3-D images of samples, but requires mechanical scanning of laser beams. But two researchers have invented a new technology called FINCH (short for 'Fresnel incoherent correlation holography.' According to them, FINCH can make 3-D imaging quicker and more accurate. Their FINCHSCOPE, a 3-D microscope, promises to capture high-resolution 3-D fluorescent images of biological specimens without the need for any moving parts. It could be used in medical applications such as endoscopy, CT scanning or X-ray imaging, but also for security screening or 3-D movies. But read more...
You can see above a comparison of the FINCH principle and conventional imaging: "a, In a conventional imaging system each point on the observed plane is copied onto the imaging plane or the image sensor. Points that are out of the observed plane are obtained as blurred spots on the imaging plane. The depth difference between points is not memorized in a conventional imaging system and information from objects out of focus is lost. b, FINCH, on the other hand, projects a set of rings known as Fresnel zone plates for all points. The depth of the points is encoded by the density of the rings. In other words, points closer to the system project less dense rings than distant points. Therefore, the depth difference between points is memorized in the FINCH system and can be recovered in focus by the computer."(Credit: Johns Hopkins University, via Nature Photonics). Here is a link to a larger version of this figure.
This technology has been co-invented by Gary Brooker, a research professor of chemistry and director of the Microscopy Center at Johns Hopkins University, and by Joseph Rosen, professor of electrical and computer engineering at Ben-Gurion University of the Negev in Israel, who is currently on leave. Together, they have founded CellOptic, Inc., which owns the FINCH technology.
Here is a quote by Brooker about this FINCH technology. "Normally, 3-D imaging requires taking multiple images on multiple planes and then reconstructing the images. This is a slow process that is restricted to microscope objectives that have less than optimal resolving power. For this reason, holography currently is not widely applied to the field of 3-D fluorescence microscopic imaging."
In this research project, the two professors focused on 3-D still images, but animated ones are coming. Here is another quote from the researchers. "With traditional 3-D imaging, you cannot capture a moving object. With the FINCHSCOPE, you can photograph multiple planes at once, enabling you to capture a 3-D image of a moving object. Researchers now will be able to track biological events happening quickly in cells. In addition, the FINCH technique shows great promise in rapidly recording 3-D information in any scene, independent of illumination."
This research work has been accepted by Nature Photonics as an advance online publication under the thtile "Non-scanning motionless fluorescence three-dimensional holographic microscopy" on February 17, 2008. Here is an excerpt from the abstract. "Holography is an attractive imaging technique as it offers the ability to view a complete three-dimensional volume from one image. However, holography is not widely applied to the field of three-dimensional fluorescence microscopic imaging, because fluorescence is incoherent and creating holograms requires a coherent interferometer system. [...] Here we present the first demonstration of a motionless microscopy system (FINCHSCOPE) based on Fresnel incoherent correlation holography, and its use in recording high-resolution three-dimensional fluorescent images of biological specimens."
And here is a link to the full technical paper (PDF format, 6 pages, 745 KB), from which the figure above has been extracted.
Sources: Johns Hopkins University news release, February 14, 2007; and various websites
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