• 03.02.11

Opto-Phone Reads Vital Signs (And Cell Phone Conversations) via Laser From 100 Meters

What if you could walk into a hospital waiting room and an invisible beam of light discreetly detected whether you were feeling fine or were feverish, dizzy, drunk, or dehydrated?

What if you could walk into a hospital waiting room and an invisible beam of light discreetly detected whether you were feeling fine or were feverish, dizzy, drunk, or dehydrated?


Javier Garcia at the University of Valencia in Spain and Zeev Zalevsky at the Bar-Ilan University in Israel see it happening. Soon. They’re aiming to revolutionize healthcare with an optical phone that can hear a person’s heartbeat, measure their blood pressure, and even gauge their blood glucose levels, all from up to 100 meters away. Utilized for surveillance, it will allow sleuths to remotely listen in on or even tape cell phone conversations. 

The duo’s “opto-phone” hears sounds by shining a focused laser beam on the person. Since skin or cloth is non-uniform, it produces an interference pattern called a “speckle pattern” that changes in response to the way the surface moves. Zalvesky extracts the parts of the changing pattern that contain audio with the aid of a sensitive camera and advanced software. Shining a small laser spot on a person’s forehead, neck, or cheek, for example, allows the opto-phone user to listen to a conversation, but training the laser on someone’s chest or wrist allows the user to extract heartbeat and blood pressure information.

“Different locations in the body give different types of signals,” Zalvesky tells Fast Company. “The speckles generated in the face can be used for listening to speech and the speckles generated on the chest can be used for biomedical monitoring.”

The team made the breakthrough after three years of attempting to overcome problems faced by current laser-based listening devices used in surveillance–many are tedious to operate. The person being monitored needs to be near a window or surface (to read the sound vibrations off of), and the laser and detection modules have to be placed at the right angles. Trying to extract the relevant sounds is a nightmare, since it is mixed up with sounds from the environment.

In contrast, Zalevsky’s technique allows everything that’s illuminated within the laser spot, to be heard even in extremely noisy environments.

Eric Miller, Associate Dean of Research at the Tufts School of Engineering, finds the approach compelling. “Zalevsky seems to have developed a system for doing optical speckle interferometry that is practical and robust, overcoming a number of important challenges which they’ve demonstrated in practice,” he tells Fast Company.

The exciting part is that the fundamental technique can be used to create an entire range of devices. Remotely monitoring every patient in a hospital room or keeping tabs on a person’s vital signs in the operating theater would be child’s play. It would be possible to produce “optical cardiograms” by measuring a person’s heartbeats from a distance. A handheld version that monitors vital signs from a distance could come eerily close to the very popular medical “tricorder” in Star Trek.


Hard at work on creating a watch sized version, Zalevsky hopes to have a working prototype within a year’s time that can remotely detect blood pressure or blood glucose levels. (Changes in blood viscosity change the way the skin vibrates in any organ that is close to a major blood artery.) Plans to create a laser-based hearing aid are also in the works.

The team is presently focused on making the technology undetectable, by getting it to work with infrared light instead of green light.

John Wallace, Senior Editor at Laser Focus World thinks it could have some unsettling uses in surveillance. “If I had such a device, I could, for example, sit in a football stadium during a game and listen in on anyone in the stadium I wanted to,” he says.

Wallace believes that it would be easy create a small battery-powered version that functioned as an ‘audiocam’ which anyone could use and that it could eventually lead to a new way of disseminating information.

“Someday, perhaps, some of those snippets of information that get posted on Facebook or Youtube and subsequently go viral will contain voice clips recorded remotely with a laser audiocam.”

[Image: garagegy on Photobucket]