Transient imaging is a recent imaging modality in which short pulses of light are observed ``in flight'' as they propagate through a scene. Transient images are useful to help understand light propagation in complex environments and to analyze light transport for research and many practical applications. Two such examples are the reconstruction of occluded geometry, i.e. ``looking around a corner'', or measuring surface reflectance. Unfortunately, advances in research and practical applications have so far been hindered by the high cost of the required instrumentation, as well as the fragility and difficulty to operate and calibrate devices such as femtosecond lasers and streak cameras.
To address this, we present a device that allows inexpensive and fast transient imaging using photonic mixer devices (PMDs). Our portable device achieves this by capturing a sequence of modulated images with a PMD sensor and inferring a transient image using numerical optimization and a mathematical model for local light interactions. By doing so, the cost of transient imaging is reduced by several orders of magnitude and the capture process is dramatically sped up and simplified.
We envision that in the future not only research but virtually everybody has access to inexpensive, fast and portable transient-image cameras with its many emerging applications.