Asynchronous Double-Frame-Exposure Binocular-Camera With Pixel-Level Pipeline Architecture for High-Speed Motion Tracking

Abstract

The synchronous double-frame exposure (S-DFE), also called frame-straddling, has been widely applied for commercial video-based velocity measurements to provide high-speed velocimetry-flow images. Nevertheless, no low-cost, high-speed cameras offer the video quality that researchers, scientists, and industry demand. This brief presents an asynchronous DFE (A-DFE) method with a binocular camera for motion estimation, which captures double frames with the scalable time interval of the dual generic cameras. This time interval can significantly improve the upper limit of displacements of the motion, which is commonly solved by an expensive high-speed camera. A dedicated hardware architecture is designed to implement the perspective transformation and Wallis filter to eliminate the two cameras’ position mismatch and brightness variance. We build a high-speed Lucas-Kanade optical flow estimation system with A-DFE on the XILINX Spartan-7 FPGA platform with MT9V034 CMOS image sensors. The shortest time interval can reach 1.06 ns, which means a significant improvement of the upper limit of the measurement velocity. Except for the image sensor, the compact, fully parallel architecture can attain energy efficiency with 3.23 nJ/pixel on a low-cost FPGA device.