Single-Pixel Imaging Enables Ultrafast 3D Object Tracking

Researchers have created a new 3D technique to track fast-moving objects at previously unheard-of speeds. Based on single-pixel imaging, the real-time tracking approach has the potential to enhance security surveillance, industrial inspection, and autonomous driving systems. The study has been published in the Optica Publishing Group journal Optics Letters.

Researchers developed a new 3D method that can be used to track fast-moving objects at unprecedented high speeds. The optical setup for their experiments is shown. Image Credit: Zihan Geng, Tsinghua University

Our approach does not require reconstructing the object’s image to calculate its position, which significantly reduces data storage and computational costs. Specifically, acquiring a 3D coordinate requires only 6 bytes of storage space and 2.4 µs of computation time. By reducing computational costs and improving efficiency, it could lower the cost of equipment needed for high-speed tracking, making the technology more accessible and enabling new applications.

Zihan Geng, Research Team Leader, Tsinghua University

The researchers demonstrated a tracking speed that is more than 200 times faster than conventional video-based techniques. The tracking approach uses the least amount of computational power and does not require any previous motion data.

This technology could enhance the perception abilities of technologies like self-driving cars, improve security surveillance systems, and offer more efficient monitoring and quality control for industrial inspection. Additionally, this high-speed localization technique can be used in scientific research, such as insect flight trajectory studies.

Zihan Geng, Research Team Leader, Tsinghua University

Improving Usability

A computational technique known as “single-pixel imaging” uses a single detector to collect measurements rather than a conventional array of pixels. Usually, a scene is illuminated with a series of patterns, and a single-pixel detector measures the corresponding intensity values.

Instead of using the more common orthogonal method, the researchers used a more efficient non-orthogonal projection approach to create a more useful single-pixel imaging system for object tracking. Two non-orthogonal planes are projected with geometric light patterns to calculate the object's position, creating 3D coordinates. Additionally, non-orthogonal projection minimizes the overall system size, facilitating assembly and implementation.

High-Speed Tracking

The researchers used a single-pixel imaging setup consisting of a 532 nm laser for active illumination, a digital micromirror device (DMD) with a 20 kHz modulation rate to create the light patterns, and two single-pixel detectors to collect the light signals after verifying the method with simulations.

They utilized a metal sphere with a central hole and curved spiral wire to test the tracking ability by allowing it to move while being lit in different patterns. The object’s 3D position was determined using the signals from the detectors, and its calculated motion trajectory was then obtained by rotating the coordinate system. Using this method, they could use the DMD at a modulation rate of 20 kHz and achieve a tracking rate of 6667 Hz.

According to the researchers, the main issue with this technology is that it can only be used to track a single object at this time. Researchers are currently working on techniques that will enable single-pixel imaging to track multiple objects.

Journal Reference:

Zhang, H., et al. (2024) Prior-free 3D tracking of a fast-moving object at 6667 frames per second with single-pixel detectors. Optics Letters.

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