Deng Rujia, Jin Xin, Du Dongyu, Li Zhiheng
Opt Express. 2023 Jul 3;31(14):23662-23677. doi: 10.1364/OE.492864.
Reconstructing an object's three-dimensional shape behind a scattering layer with a single exposure is of great significance in real-life applications. However, due to the little information captured by a single exposure while strongly perturbed by the scattering layer and encoded by free-space propagation, existing methods cannot achieve scan-free three-dimensional reconstruction through the scattering layer in macroscopic scenarios using a short acquisition time of seconds. In this paper, we proposed a scan-free time-of-flight-based three-dimensional reconstruction method based on explicitly modeling and inverting the time-of-flight-based scattering light propagation in a non-confocal imaging system. The non-confocal time-of-flight-based scattering imaging model is developed to map the three-dimensional object shape information to the time-resolved measurements, by encoding the three-dimensional object shape into the free-space propagation result and then convolving with the scattering blur kernel derived from the diffusion equation. To solve the inverse problem, a three-dimensional shape reconstruction algorithm consisting of the deconvolution and diffractive wave propagation is developed to invert the effects caused by the scattering diffusion and the free-space propagation, which reshapes the temporal and spatial distribution of scattered signal photons and recovers the object shape information. Experiments on a real scattering imaging system are conducted to demonstrate the effectiveness of the proposed method. The single exposure used in the experiment only takes 3.5 s, which is more than 200 times faster than confocal scanning methods. Experimental results show that the proposed method outperforms existing methods in terms of three-dimensional reconstruction accuracy and imaging limit subjectively and objectively. Even though the signal photons captured by a single exposure are too highly scattered and attenuated to present any valid information in time gating, the proposed method can reconstruct three-dimensional objects located behind the scattering layer of 9.6 transport mean free paths (TMFPs), corresponding to the round-trip scattering length of 19.2 TMFPs.
单次曝光重建散射层后物体的三维形状在实际应用中具有重要意义。然而，由于单次曝光捕获的信息很少，同时受到散射层的强烈干扰并由自由空间传播进行编码，现有方法无法在宏观场景中使用几秒的短采集时间通过散射层实现无扫描三维重建。在本文中，我们提出了一种基于飞行时间的无扫描三维重建方法，该方法基于对非共焦成像系统中基于飞行时间的散射光传播进行显式建模和反演。开发了基于非共焦飞行时间的散射成像模型，通过将三维物体形状编码到自由空间传播结果中，然后与从扩散方程导出的散射模糊核进行卷积，将三维物体形状信息映射到时间分辨测量中。为了解决反问题，开发了一种由去卷积和衍射波传播组成的三维形状重建算法，以反演由散射扩散和自由空间传播引起的影响，从而重塑散射信号光子的时间和空间分布并恢复物体形状信息。在实际散射成像系统上进行了实验，以证明所提方法的有效性。实验中使用的单次曝光仅需3.5秒，比共焦扫描方法快200多倍。实验结果表明，所提方法在三维重建精度和成像极限方面在主观和客观上均优于现有方法。即使单次曝光捕获的信号光子散射和衰减程度过高，以至于在时间选通中无法呈现任何有效信息，所提方法仍可重建位于9.6个输运平均自由程（TMFP）散射层后面的三维物体，对应于19.2个TMFP的往返散射长度。
