A Volumetric Particle Tracking Velocimetry Technique Based On A Single Color Camera With Trichromatic Mask

To address the limitations of existing 3D flow measurement techniques—such as multicamera systems with complex calibration, high cost, and poor adaptability to confined spaces, and traditional PIV without high spatial resolution or per-particle tracking capability—this study proposes a volumetric Particle Tracking Velocimetry (PTV) technique based on a single color camera to achieve relatively accurate flow field reconstruction. Equipped with a trichromatic mask that replaces multi-camera arrays to simplify optical configurations and reduce costs, the single color camera utilizes red, green, and blue color channels to capture three distinct perspective images of tracer particles, laying the foundation for precise 3D particle reconstruction. These images are then processed via 3D PTV to reconstruct Lagrangian 3D particle tracks, with color channel separation and linear crosstalk correction based on single-aperture calibration implemented to enhance the accuracy of the three-view images. The processed three-view images are fed as inputs into the Shake-The-Box (STB) particle tracking algorithm, which employs spatiotemporal joint constraints to determine the 3D particle distribution and realize frame-to-frame tracking. The effects of particle image density (ppp), mask aperture spacing, camera magnification factor, and image noise on tracking performance and velocity measurement accuracy are analyzed using digitally synthesized flow fields and synthetic particle images—higher particle image density may lead to increased projection overlap and matching ambiguities, while elevated noise degrades the precision of particle center detection, both impairing tracking accuracy. It is found that adjusting the trichromatic mask’s key parameters essentially modifies the parallax angle between the three simulated perspectives: larger aperture spacing and smaller absolute magnification enhance the parallax angle, improving spatial resolution especially in the Z (depth) direction, while smaller spacing and larger absolute magnification reduce the parallax angle, resulting in degraded depth resolution and compromised tracking accuracy. Finally, the proposed technique is validated by reconstructing the 3D flow field around a cylinder: the single trichromatic mask-equipped color camera successfully achieves 3D vorticity field reconstruction of the cylinder wake, effectively capturing key flow structures such as periodic vortex shedding and coherent vortex streets, which confirms its practicality for complex 3D flow measurement scenarios. In conclusion, the proposed single-camera PTV technique with a trichromatic mask simplifies the measurement system, reduces costs, and enables highconcentration particle tracking while maintaining flow field characterization accuracy. Its primary limitation lies in depth-direction positioning errors induced by limited parallax angles, and future optimizations will focus on improving depth resolution to enhance overall measurement performance.