Eliminating the lens eliminates expense, says Wilbur Lam, a pediatric oncologist at the University of California, San Francisco Children's Hospital, but doctors used to looking at images under a microscope will demand better images. "Physicians are conservative," he says. Lam is working with a group of engineers that's integrating conventional, lens-based microscopy with cell phones.

The UCLA researchers are improving the quality of their images on both the software and hardware fronts. "With more advanced processing, we can do more analysis and extract an image from the shadows with a decent enough resolution to show subcellular features," says Ozcan.

The UCLA group has also made a new version of the microscope that integrates an optical trick used to enhance image contrast on conventional microscopes. This method, called differential interference contrast, uses a prism to split the light beam into two beams with different polarizations before it illuminates the sample, and a second prism to recombine it after it passes through the sample. Combining the two beams produces an image with enhanced edge contrast. This method makes it possible to see many types of bacteria that are transparent, without the use of a stain. Adding interference contrast to a conventional microscope costs about $1,000 because the prisms must each be painstakingly aligned with lenses. The UCLA method is holographic, in effect generating two images of each cell, each made with light of a different polarization. These images are processed and recombined to get more information on a sample and to produce better contrast.

In the UCLA microscope, the phase-contrast elements can be added and removed through the same small drawer where the sample is loaded because there are no other elements to line up with. The only cost is the $2 materials cost of the prisms, 100-micrometer-thick films of quartz crystal, bringing the total cost of the imager to about $3.

Ozcan is currently working with a startup company called Holoscope, based in Santa Monica, CA, to develop the microscope. He says the company will develop the microscopes along two lines, one for the educational market and one for performing complete blood counts.