at a digital sensor array. This data is filtered to remove unwanted information,
and a computer then digitally reconstructs
an image of the specimen. The device also
has a transmission mode.
The light weight and low cost of the device would be particularly beneficial during
field work in the developing world. Possible applications include screening of blood
for pathogens or testing of water quality.
For such uses, what is needed sometimes is
a microscope with adequate resolution but
a very wide field of view because what is
being searched for is not common.
“If you look at malaria slide readings,
it’s a rare event problem. Around 1 percent of the red blood cells show malaria
signatures,” Ozcan said.
He added that extensions to the idea involve lens-free fluorescence imaging and
resolution improvements at the submicron
level. Along with others, he has formed a
company, Holomic LLC, to commercialize
the concept.
Optical materials and the phone
Such efforts point the way toward an increasingly important factor that affects optical materials – and vice versa. The advent
of smartphones promises to change microscopy, spectroscopy and other areas because
smartphones have high-resolution displays,
megapixel cameras, storage and connectivity, and they offer powerful local computing. When combined with simple attachments, they can make surprisingly capable
microscopes and other optical devices.
An example can be seen in the work of
Ramesh Raskar, an associate professor at
the MIT Media Lab. While developing a
new bar-code system, he realized that it
could be used to make a refraction map of
the eye, something traditionally done by a
doctor when figuring out an eyeglass prescription.
This mapping now can be done using a
smartphone and an inexpensive attachment.
Software creates a carefully arranged pattern of lines or dots on the display, and then
it puts the patient to work.
“We ask the user to create changes in
the position of the dots,” Raskar said.
The adjustments reveal refractive distortions in the eye. Because uncorrected
vision problems are a leading cause of
blindness for millions worldwide, such a
device could be very beneficial. That’s the
idea behind EyeNETRA, a company
formed to commercialize the concept.
Vitor Fernando Pamplona, a graduate student who was at the MIT Media Lab and
is now at Brazil’s Federal University of
Rio Grande do Sul in Porto Alegre, developed the smartphone eye doctor technique
as part of his thesis and is involved with
EyeNETRA.
When it comes to getting the device
into the field, Pamplona said one idea
would be a microbusiness model, with
people in large cities in the developing
world paying for the ability to run a set of
tests. These buyers would then travel to
the countryside, where they would perform an eye exam in return for payment.
The test itself would likely be an aide,
helping people decide whether they need
to see a doctor.
Other vision problems also could be
discovered by a similar combination of a
smartphone, an attachment, software and
the right techniques. Pamplona demon-
strated that this setup can be used to find
cataracts, something done today with a
machine developed nearly 50 years ago
and that can take months to master. The
fact that a phone can match its perform-
ance isn’t that surprising, given the tech-
nology available.
Reference
1. N. Fang et al (2005). Sub-diffraction-limited
optical imaging with a silver superlens.
Science, Vol. 308, pp. 534-537.
