Multi-scale band-limited illumination profilometry for robust three-dimensional surface imaging at video rate.

Dynamic three-dimensional (3D) surface imaging by phase-shifting fringe projection profilometry has been widely implemented in diverse applications. However, existing techniques fall short in simultaneously providing the robustness in solving spatially isolated 3D objects, the tolerance of large variation in surface reflectance, and the flexibility of tunable working distances with meter-square-level fields of view (FOVs) at video rate. In this work, we overcome these limitations by developing multi-scale band-limited illumination profilometry (MS-BLIP). Supported by the synergy of dual-level intensity projection, multi-frequency fringe projection, and an iterative method for distortion compensation, MS-BLIP can accurately discern spatially separated 3D objects with highly varying reflectance. MS-BLIP is demonstrated by dynamic 3D imaging of a translating engineered box and a rotating vase. With an FOV of up to 1.7 m × 1.1 m and a working distance of up to 2.8 m, MS-BLIP is applied to capturing full human-body movements at video rate.

Camera-free three-dimensional dual photography.

We report camera-free three-dimensional (3D) dual photography. Inspired by the linkage between fringe projection profilometry (FPP) and dual photography, we propose to implement coordinate mapping to simultaneously sense the direct component of the light transport matrix and the surface profiles of 3D objects. By exploiting Helmholtz reciprocity, dual photography and scene relighting can thus be performed on 3D images. To verify the proposed imaging method, we have developed a single-pixel imaging system based on two digital micromirror devices (DMDs). Binary cyclic S-matrix patterns and binary sinusoidal fringe patterns are loaded on each DMD for scene encoding and virtual fringe projection, respectively. Using this system, we have demonstrated viewing and relighting 3D images at user-selectable perspectives. Our work extends the conceptual scope and the imaging capability of dual photography.

Real-time high-speed three-dimensional surface imaging using band-limited illumination profilometry with a CoaXPress interface.

High-speed three-dimensional (3D) surface imaging by structured-light profilometry is currently driven by numerous applications. However, the limited speeds in fringe pattern projection, image acquisition, and data transmission have strained the existing methods from reaching kilohertz-level acquisition, processing, and display of 3D information during the occurrence of dynamic events (i.e., in real time). To overcome these limitations, we have developed band-limited illumination profilometry (BLIP) with a CoaXPress interface (CI), which enables real-time high-speed 3D surface imaging. We have demonstrated the system's performance by imaging various static and fast-moving 3D objects in real time. We have also applied this system in fluid mechanics by imaging dynamics of a flag, which allowed observation of the wave propagation, gravity-induced phase mismatch, and asymmetric flapping motion. We expect CI-BLIP to find diverse scientific and industrial applications.

Compressed ultrahigh-speed single-pixel imaging by swept aggregate patterns.

Single-pixel imaging (SPI) has emerged as a powerful technique that uses coded wide-field illumination with sampling by a single-point detector. Most SPI systems are limited by the refresh rates of digital micromirror devices (DMDs) and time-consuming iterations in compressed-sensing (CS)-based reconstruction. Recent efforts in overcoming the speed limit in SPI, such as the use of fast-moving mechanical masks, suffer from low reconfigurability and/or reduced accuracy. To address these challenges, we develop SPI accelerated via swept aggregate patterns (SPI-ASAP) that combines a DMD with laser scanning hardware to achieve pattern projection rates of up to 14.1 MHz and tunable frame sizes of up to 101×103 pixels. Meanwhile, leveraging the structural properties of S-cyclic matrices, a lightweight CS reconstruction algorithm, fully compatible with parallel computing, is developed for real-time video streaming at 100 frames per second (fps). SPI-ASAP allows reconfigurable imaging in both transmission and reflection modes, dynamic imaging under strong ambient light, and offline ultrahigh-speed imaging at speeds of up to 12,000 fps.