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Real-time 3D Structured Light System
Related Articles
[1] Dual-frequency Pattern Scheme for High-speed 3-D Shape Measurement.
[2] Maximum SNR Pattern Strategy for Phase Shifting Methods in Structured Light Illumination.
[3] Real-Time Three-Dimensional Shape Measurement of Moving Objects without Edge Errors by Time Synchronized Structured Illumination.
System Overview
Structured light illumination (SLI) is the process of projecting a series of light striped patterns such that, when viewed at an angle, a digital camera can reconstruct a 3-D model of a target object's surface.
Our high-resolution, real-time 3D structured light system employs the state-of-art pattern strategies and novel high-speed reconstruction methods and can realize acquisition and
reconstruction at 120 frames per second (fps) with 640*480 points per frame. In addition, the system is very scalable which means various needs can be satisfied. Currently, several technical articles have been accepted or submitted.
A good platform is provided by this real-time 3D system for various researches and applications including machine vision, computer science, biometrics, manufacturing, medical sciences, and entertainment. This results and videos are available which explain the advantages of our technology.
* Real-time 3D scanning and reconstruction of a stationary textured angel and a moving hand. The frame rate is 120 fps. The real-time displayed 3D result is shown in depth pseudo color.
Pattern Strategies
In order to enhance the signal to noise ratio, we developed optimized edge pattern strategy, with minimum number of patterns 3. Further, since the accuracy of phase shift patterns increases with the number of periods which also introduces ambiguity in phase, we developed two pattern strategies, namely Period Coded pattern strategy and Dual Phase Multiplexing pattern strategy, which unwrap the high frequency phase without projecting more patterns or using complicated spatial unwrapping methods.
High-speed Reconstruction
As a series of time multiplexed patterns, SLI is not typically associated with video applications unless the projector/camera pair can be driven at very high frame rates such that any object motion is small over the pattern set, but at these high frame rates, the speed at which the incoming video can be processed becomes an issue. So much so that many video-based SLI systems record camera frames to memory and then apply off-line processing to the data to reconstruct 3D video. In order to overcome this processing bottleneck and produce 3D point clouds in real-time, we developed a novel Lookup Table based solution that in our experiments, using a 640*480 video stream, can generate intermediate phase data at 1063.8 frames per second and full 3D point clouds at 228.3 frames per second. These achievements are 25 and 10 times faster than previously reported studies.
* The test results are based on full image of 640*480 points, using one core of an Intel Core 2 Duo Quad Q9650 processor.
The phase processing technique is applicable to most phase shifted methods. The 3D point reconstruction technique is applicable to all triangulation based 3D techniques (including SLI, stereo vision, laser scan, time-of-flight and so on).
Results and Videos
* The depth rendering result using 4 patterns 16 periods pattern strategy. Frame rate is 120 fps. No filter is applied.
* 3D reconstructions for different number of patterns strategies. No filter is applied. (a) Scanned Object. (b) The depth rendering result using 3 patterns 4 periods pattern strategy. (c) The depth rendering result using 4 patterns 16 periods pattern strategy. (d) The depth rendering result using 6 patterns 32 periods pattern strategy.
* The live show using 6 patterns 16 periods pattern strategy. Frame rate is 120 fps. No filter is applied.
The video, which further explains the advantages of our technology, is available for downloading.
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