MICROSCOPES are invaluable tools to identify blood and other cells when screening for diseases like anemia, tuberculosis and malaria. But they are also bulky and expensive.

Now an engineer, using software that he developed and about $10 worth of off-the-shelf hardware, has adapted cellphones to substitute for microscopes.

“We convert cellphones into devices that diagnose diseases,” said Aydogan Ozcan, an assistant professor of electrical engineering and member of the California NanoSystems Institute at the University of California, Los Angeles, who created the devices. He has formed a company, Microskia, to commercialize the technology.

The adapted phones may be used for screening in places far from hospitals, technicians or diagnostic laboratories, Dr. Ozcan said.