UCLA creates cheap light-weight lens-free microscope using holograms
20 September 2011
Researchers at the University of California at Los Angeles
(UCLA) have built a compact, light-weight, dual-mode microscope that
uses holograms instead of lenses.
The prototype weighs about as much as a medium-sized banana and
fits in the palm of a hand. And, since it relies in part on
mass-produced consumer electronics, all the materials to make it add
up to between US$50 and US$100.
It also has a two-in-one feature: a transmission mode that can be
used to probe relatively large volumes of blood or water, and a
reflection mode that can image denser, opaque samples. The spatial
resolution for both modes is less than two micrometers — comparable
to that achieved by bulkier microscopes with low to medium-power
lenses. The device
is described in a paper published in the Optical Society’s (OSA)
open-access journal Biomedical Optics Express .
The hologram microscope in transmission mode,
which gives it a wider field of view, for searching large volumes of
see-through material such as blood or water.
“This is the first demonstration of essentially a hand-held
version of a microscope that can do dual-mode imaging within a very
compact and cost-effective form,” says Aydogan Ozcan, an associate
professor of electrical engineering and bioengineering at UCLA and
senior author of the paper.
With just a small amount of training, doctors could use devices
like these to improve health care in remote areas of the world with
little access to diagnostic equipment, Ozcan says. The handheld
microscope could help ensure water quality, test patients’ blood for
harmful bacteria, and even be used for semen-quality monitoring on
It could also prove useful in health crises such as the recent
outbreak of E. coli in Europe.
“It’s a very challenging task to detect E. coli in low
concentrations in water and food,” Ozcan says. “This microscope
could be part of a solution for field investigation of water, or
food, or maybe pathogens in blood.”
Part of the device’s success is the weight it shed when
researchers got rid of the bulkier, heavier, more expensive pieces
that most microscopes rely on for collecting and focusing light: the
lenses. Instead of lenses, this microscope uses holograms.
Holograms are formed when light bouncing off (or passing through)
a three-dimensional object is made to interfere with a “reference
beam,” or light that has not hit the object. Consider this analogy:
drop a stone into a still pond and the ripples will move outward in
a circle. Drop two stones and the circular ripples will interfere
with each other, making a new pattern of crests and troughs. A
person (or computer) analyzing the interference pattern created by
those two stones could trace the source back to the stones and
recreate what had happened to make the waves.
The UCLA team’s device uses a similar principle to recreate
images from interfering light waves. An inexpensive laser light source is divided into two beams — one that
interacts with microscopic cells or particles in the sample, and the
other that does not. The beams then pass to an adjacent sensor chip,
where their interference pattern is recorded.
Software then analyzes that pattern and recreates the path taken
by the light that passed through or bounced off of the objects being
Each component of the device is fairly inexpensive, Ozcan says.
The laser light could come from a $5 laser pointer. The sensor chip
that collects that light is the same as the ones in the backs of
iPhones and Blackberrys and costs less than $15 per chip. And the
whole image-collecting system runs on two AA batteries.
Where the researchers have reduced weight and expense in doing
away with lenses, they have added the power of the cloud. The
microscope captures raw data; but a computer is required to
reconstruct the images. Workers in the field could use their laptops
to process the information or send it over the Internet or mobile
phone networks to a remote server. Mobile phones could also have
sufficient processing power to do the analysis on the spot.
Essentially, Ozcan says, “we are replacing an expensive and
bulky, heavy component with computer codes.”
The next steps for Ozcan’s team include commercializing the
device. Ozcan says he has founded a company that is developing this
technology, trying to make a version of the microscopes that can be
manufactured and sold to healthcare workers and hobbyists.
“Global health is a big field that requires better diagnostic
tools, because resource-poor countries don’t have the infrastructure
for conducting essentially accurate diagnostic tests,” Ozcan says.
“There are so many problems that innovative solutions [like this
microscope] would impact.”
1. M. Lee, O. Yaglidere, A. Ozcan. Field-portable reflection and
transmission microscopy based on lensless holography. Biomedical
Optics Express, Volume 2, Issue 9, p. 2721-2730.