A new method to record biological events at the molecular level, using holographic technology, has been developed at New York University. The technology uses a microscope that illuminates targets with a collimated laser beam, and that results in a diffraction pattern, which is reinterpreted by the system as a hologram so it can be viewed by the researchers:
NYU press office explains:
The scattered light overlaps with the original beam to create an interference pattern reminiscent of overlapping ripples in a pool of water. The microscope then magnifies the resulting pattern of light and dark and records it with a conventional digital video recorder (DVR). Each snapshot in the resulting video stream is a hologram of the original object. Unlike a conventional photograph, each holographic snapshot stores information about the three-dimensional structure and composition of the object that created the scattered light field.
The recorded holograms appear as a pattern of concentric light and dark rings. This resulting pattern contains a wealth of information about the material that originally scattered the light-where it was and what it was comprised of.
Analyzing the images provided a different set of challenges. To do so, the researchers based their work on a quantitative theory explaining the pattern of light that objects scatter. The theory, Lorenz-Mie theory, maintains that the way light is scattered can reveal the size and composition of the object that is scattering it.
“We use that theory to analyze the hologram of each object in the snapshots of our video recording,” explained [David] Grier, who is part of NYU’s Center for Soft Matter Research. “Fitting the theory to the hologram of a sphere reveals the three-dimensional position of the sphere’s center with remarkable resolution. It allows us to view particles a micrometer in size and with nanometric precision-that is, it captures their traits to within one billionth of a meter.”
“That’s a tremendous amount of information to obtain about a micrometer-scale object, particularly when you consider that you get all of that information in each snapshot,” Grier added. “It exceeds other existing technology in terms of tracking particles and characterizing their make-up-and the holographic microscope can do both simultaneously.”
Because the analysis is computationally intensive, the researchers employ the number-crunching power of the graphical processing unit (GPU) used in high-end computer video cards. Originally intended to provide high-resolution video performance for computer games, these cards possess capabilities ideal for the holographic microscope.