IEEE Trans Pattern Anal Mach Intell. 2017 May;39(5):937-950. doi: 10.1109/TPAMI.2016.2560814. Epub 2016 Apr 29.
A transient image is the optical impulse response of a scene, which also visualizes the propagation of light during an ultra-short time interval. In contrast to the previous transient imaging which samples in the time domain using an ultra-fast imaging system, this paper proposes transient imaging in the frequency domain using a multi-frequency time-of-flight (ToF) camera. Our analysis reveals the Fourier relationship between transient images and the measurements of a multi-frequency ToF camera, and identifies the causes of the systematic error-non-sinusoidal and frequency-varying waveforms and limited frequency range of the modulation signal. Based on the analysis we propose a novel framework of frequency-domain transient imaging. By removing the systematic error and exploiting the harmonic components inside the measurements, we achieves high quality reconstruction results. Moreover, our technique significantly reduces the computational cost of ToF camera based transient image reconstruction, especially reduces the memory usage, such that it is feasible for the reconstruction of transient images at extremely small time steps. The effectiveness of frequency-domain transient imaging is tested on synthetic data, real data from the web, and real data acquired by our prototype camera.
瞬态图像是场景的光脉冲响应，也可以可视化超短时间间隔内的光传播。与以前使用超快成像系统在时域中进行采样的瞬态成像不同，本文提出了使用多频飞行时间 (ToF) 相机在频域中进行瞬态成像。我们的分析揭示了瞬态图像与多频 ToF 相机测量之间的傅里叶关系，并确定了系统误差（非正弦和频率变化的波形以及调制信号的有限频率范围）的原因。基于该分析，我们提出了一种新的频域瞬态成像框架。通过去除系统误差并利用测量中的谐波分量，我们实现了高质量的重建结果。此外，我们的技术显著降低了基于 ToF 相机的瞬态图像重建的计算成本，特别是降低了内存使用，使得在极短的时间步长下重建瞬态图像成为可能。频域瞬态成像的有效性在合成数据、来自网络的真实数据和我们原型相机采集的真实数据上进行了测试。
