The harmony of art and science: droplet holography
Sep/23/2009 21:46 Filed in: News
Little drops of water
Little grains of sand
Make the mighty ocean
And the beauteous land….
so wrote Mrs. J.A. Carney in 1845. Artists like Martin Waugh have wonderful pictures of water drops (and ice crystals) exhibited as liquid sculptures (see, for instance, http://www.liquidsculpture.com/fine_art/). A picture, however, is only two-dimensional. At the University of Dayton (UD), researchers are looking into the detailed nature of these little drops, using holography to recreate their exact three-dimensional shape in order to understand how exactly they deform when they impact fast moving surfaces such as the windshields of aircraft traveling through rain.
so wrote Mrs. J.A. Carney in 1845. Artists like Martin Waugh have wonderful pictures of water drops (and ice crystals) exhibited as liquid sculptures (see, for instance, http://www.liquidsculpture.com/fine_art/). A picture, however, is only two-dimensional. At the University of Dayton (UD), researchers are looking into the detailed nature of these little drops, using holography to recreate their exact three-dimensional shape in order to understand how exactly they deform when they impact fast moving surfaces such as the windshields of aircraft traveling through rain.
Professor Partha Banerjee and Dr. Georges Nehmetallah from the Electro-Optics Program and the Department of Electrical and Computer Engineering at UD have teamed with DMS Technologies from Huntsville, Alabama, the Aviation and Missile Command (AMCOM), Alabama A&M University, and the University of Alabama in Huntsville to develop high-speed holographic interferometry to study droplet demise during high-speed impact with the shock layers around supersonic vehicles. Their initial work, funded through a $100 K Phase I Army grant, has now blossomed into a Phase II $720 K contract for a two-year research program, in which UD’s take is $330K. DMS Technologies is also a partner in IDCAST, and is working on commercialization of some of the joint research with UD, such as detection of contaminants such as bacterial micro-organisms in water supplies.
At the Optical Information Processing Laboratory at UD which is recently relocating to its new habitat in the College Park Center, an argon-ion laser illuminates a droplet suspended from a dropper and images it to a CCD camera. The result is already a fascinating image (top picture) that shows details of the droplet including the colorful caustics, as well as tiny air bubbles that zip inside the droplet and bounce back and forth from the surface. To record the depth information, the researchers superpose on this picture a reference beam, which creates a hologram of the droplet (middle). The fringes on the picture of the droplet are much like Newton’s rings in a standard physics book. By using sophisticated image processing techniques, Banerjee and Nehmetallah then recreate the three-dimensional picture of the droplet, as shown in the bottom picture. With the grant, Banerjee and Nehmetallah are now devising ways to automate the process, develop high speed holographic techniques using high speed recording cameras to vividly picture and analyze droplet demise that would occur in time scales in the order of microseconds as a shock layer interacts with the droplets.
Commercial applications of this are far-reaching as well. One could use this technique to determine the impact characteristics of ink particles from inkjet printers on paper, and design faster and crisper imprints. The technique can be used in nondestructively evaluating the quality of sand-blasting during machining. Researchers in Europe have started using a similar technique using lasers and tomography to determine the true three-dimensional picture of ice crystals in the Alps as a way of monitoring global warming.
Picture of a water droplet suspended from a dropper. Note the edge of the dropper at the top of the picture.
A portion of the hologram of the same water droplet.
Computer generated reconstruction of the droplet from the hologram, which can be rotated in any orientation to view the entire 3-D image. In this view, the dropper is on the left side.
At the Optical Information Processing Laboratory at UD which is recently relocating to its new habitat in the College Park Center, an argon-ion laser illuminates a droplet suspended from a dropper and images it to a CCD camera. The result is already a fascinating image (top picture) that shows details of the droplet including the colorful caustics, as well as tiny air bubbles that zip inside the droplet and bounce back and forth from the surface. To record the depth information, the researchers superpose on this picture a reference beam, which creates a hologram of the droplet (middle). The fringes on the picture of the droplet are much like Newton’s rings in a standard physics book. By using sophisticated image processing techniques, Banerjee and Nehmetallah then recreate the three-dimensional picture of the droplet, as shown in the bottom picture. With the grant, Banerjee and Nehmetallah are now devising ways to automate the process, develop high speed holographic techniques using high speed recording cameras to vividly picture and analyze droplet demise that would occur in time scales in the order of microseconds as a shock layer interacts with the droplets.
Commercial applications of this are far-reaching as well. One could use this technique to determine the impact characteristics of ink particles from inkjet printers on paper, and design faster and crisper imprints. The technique can be used in nondestructively evaluating the quality of sand-blasting during machining. Researchers in Europe have started using a similar technique using lasers and tomography to determine the true three-dimensional picture of ice crystals in the Alps as a way of monitoring global warming.
Picture of a water droplet suspended from a dropper. Note the edge of the dropper at the top of the picture.
A portion of the hologram of the same water droplet.
Computer generated reconstruction of the droplet from the hologram, which can be rotated in any orientation to view the entire 3-D image. In this view, the dropper is on the left side.