Laser Microphone

Introduction

A laser spot illuminating a vibrating surface should move along with it, and tracking the motion of the spot should theoretically allow us to retrieve some of the information regarding the vibrations of the surface. If a loud enough sound causes the surface to vibrate, this should theoretically be enough for the transmission of audio information through visual means.

Methods and Requirements

Currently, we intend to attempt this with three different methods.

1. Using a smartphone camera, we try using object tracking and other visual processing techniques to retrieve an audio waveform from a laser spot illuminating a vibrating surface.

2. Using a photodiode / array of photodiodes, we attempt to do the same thing but possibly requiring different signal processing techniques.

3. Using a calibrated Michelson interferometer, we can attempt to detect smaller vibrations to try to retrieve the waveform, this requires more precise optical setup and measurement along with signal processing.

Due to the nature of the setups mentioned, we require a decently dim environment to minimise noise, a visible light laser (does not need to be high powered but needs to be decently collimated), an optical bench and corresponding optics equipment to build a Michelson interferometer, a set of photodiodes that can detect the laser light and produce a signal, and an electronic setup that allows us to capture and export the signal from the photodiodes.