Methods and Apparatus for Acoustic Laser Communications

Abstract

The ability to communicate with a specific subject at a prescribed location who lacks any communications equipment opens up many intriguing possibilities. Communications across noisy rooms, hail and warn applications, and localized communications directed at only the intended recipient are a few possibilities. We disclose and show localized acoustic communications, which we call photoacoustic communications, with a listener at long standoff distances using a modulated laser transmitted toward the receiver's ear. The optically encoded information is converted into acoustic messages via the photoacoustic effect. The photoacoustic conversion of the optical information into an audible signal occurs via the absorption of the light by ambient water vapor in the near area of the receiver's ear followed by airborne acoustic transmission to the ear. The recipient requires no external communications equipment to receive audible messages.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)[0001]This application claims the priority benefit, under 35 U.S.C. 119(e), of U.S. Application No. 62 / 814,993, which was filed on Mar. 7, 2019, and is incorporated herein by reference in its entirety for all purposes.GOVERNMENT SUPPORT[0002]This invention was made with Government support under Grant No. FA8702-15-D-0001 awarded by the U.S. Air Force. The Government has certain rights in the invention.BACKGROUND[0003]In 1880, Alexander Graham Bell patented a ‘photophone’ that used modulated light to create sound. Bell's patent, U.S. Pat. No. 235,496, described how the photophone had a transmitter to modulate a beam of light and a photodetector that received the modulated beam. More recently, Rush et al. disclosed a photoacoustic speaker in U.S. Pat. No. 4,641,377, which modulated laser light was shined into “a gas absorption chamber”.[0004]Recently, there has been work investigating photoacoustic communications using air. This technique, know...

AI Technical Summary

Benefits of technology

[0009]More generally, photoacoustic communications can be used to provide physical layer security when coupled with a simple receiver. It provides a signal that is localized in three dimensions, unlike other communications protocols, such as traditional laser communication. It offers robustness and immunity to intercept not necessarily available via standard radio communications. Other limited means of transmitting audio exist, but none of them can localize and safely direct information to a single user.

Problems solved by technology

Other limited means of transmitting audio exist, but none of them can localize and safely direct information to a single user.

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