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- 3-D shape measurement (11)
- Phase shifting (6)
- Structured light (5)
- Calibration (3)
- High resolution (3)
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- Holoimage (3)
- Look-up-table (3)
- Merging (3)
- Phase error compensation (3)
- Phase-shifting (3)
- Projector (3)
- Real time (3)
- 3-D range data (2)
- Gamma (2)
- Intensity ratio (2)
- Measurement (2)
- Non-sinusoidal waveform (2)
- Texture mapping (2)
- Absolute coordinates (1)
- Digital fringe projection (1)
- Dual cameras (1)
- Gamma curve (1)
- Lookup table (1)
- Metrology (1)
- Nonsinusoidal waveform (1)
- Phase error (1)
- Phase measurement (1)
- Phase shifiting (1)
- Phase-shfting algorithm (1)
- Phase-shifting method (1)
Articles 1 - 20 of 20
Full-Text Articles in Mechanical Engineering
Three-Dimensional Data Merging Using Holoimage, Song Zhang, Shing-Tung Yau
Three-Dimensional Data Merging Using Holoimage, Song Zhang, Shing-Tung Yau
Song Zhang
Three-dimensional data merging is vital for full-field three-dimensional (3D) shape measurement. All 3D range data patches, acquired from either different sensors or the same sensor in different viewing angles, have to be merged into a single piece to facilitate future data analysis. A novel method for 3D data merging using Holoimage is proposed. Similar to the 3D shape measurement system using a phase-shifting method, Holoimage is a phase-shifting–based computer synthesized fringe image. The 3D information is retrieved from Holoimage using a phase-shifting method. If two patches of 3D data with overlapping areas are rendered by OpenGL, the overlapping areas are …
Three-Dimensional Shape Measurement Using A Structured Light System With Dual Cameras, Song Zhang, Shing-Tung Yau
Three-Dimensional Shape Measurement Using A Structured Light System With Dual Cameras, Song Zhang, Shing-Tung Yau
Song Zhang
A structured light system for three-dimensional shape measurement with single camera has the shortcoming of camera occlusion. To alleviate this problem, this paper introduces a structured light system with dual cameras for three-dimensional shape measurement. We discuss (1) system description, (2) system calibration, (3) three-dimensional data registration using the iterative closest-point (ICP) algorithm, and (4) three-dimensional data merging using holoimage. The principle of the system is introduced, and experiments are presented to verify its performance.
Absolute Phase-Assisted Three-Dimensional Data Registration For A Dual-Camera Structured Light System, Song Zhang, Shing-Tung Yau
Absolute Phase-Assisted Three-Dimensional Data Registration For A Dual-Camera Structured Light System, Song Zhang, Shing-Tung Yau
Song Zhang
For a three-dimensional shape measurement system with a single projector and multiple cameras, registering patches from different cameras is crucial. Registration usually involves a complicated and time-consuming procedure. We propose a new method that can robustly match different patches via absolute phase without significantly increasing its cost. For y and z coordinates, the transformations from one camera to the other are approximated as third-order polynomial functions of the absolute phase. The x coordinates involve only translations and scalings. These functions are calibrated and only need to be determined once. Experiments demonstrated that the alignment error is within RMS 0.7 mm …
High-Speed Three-Dimensional Shape Measurement System Using A Modified Twoplus- One Phase-Shifting Algorithm, Song Zhang, Shing-Tung Yau
High-Speed Three-Dimensional Shape Measurement System Using A Modified Twoplus- One Phase-Shifting Algorithm, Song Zhang, Shing-Tung Yau
Song Zhang
This paper describes a high-resolution, real-time, three-dimensional shape measurement system using the modified two-plus-one phase-shifting algorithm. The data acquisition speed is as high as 60frames∕s with an image resolution of 640×480pixels per frame. Experiments demonstrated that the system was able to acquire the dynamic changing objects such as facial geometric shape changes when the subject is speaking, and the modified two-plus-one phase-shifting algorithm can further alleviate the error due to motion. Applications of this system include manufacturing, online inspection, medical imaging, compute vision, and computer graphics.
3d Data Merging Using Holoimage, Song Zhang, Shing-Tung Yau
3d Data Merging Using Holoimage, Song Zhang, Shing-Tung Yau
Song Zhang
Three-dimensional data merging is critical for full-field 3-D shape measurement. 3-D range data patches, acquired either from different sensors or from the same sensor in different viewing angles, have to be merged into a single piece to facilitate future data analysis. In this research, we propose a novel method for 3-D data merging using Holoimage. Similar to the 3-D shape measurement system using a phase-shifting method, Holoimage is a phase-shifting-based computer synthesized fringe image. The virtual projector projects the phase-shifted fringe pattern onto the object, the reflected fringe images are rendered on the screen, and the Holoimage is generated by …
Phase Error Compensation For A 3-D Shape Measurement System Based On The Phase-Shifting Method, Song Zhang, Peisen S. Huang
Phase Error Compensation For A 3-D Shape Measurement System Based On The Phase-Shifting Method, Song Zhang, Peisen S. Huang
Song Zhang
This paper describes a novel phase error compensation method for reducing the measurement error caused by nonsinusoidal waveforms in phase-shifting methods. For 3-D shape measurement systems using commercial video projectors, the nonsinusoidal waveform of the projected fringe patterns as a result of the nonlinear gamma of projectors causes significant phase measurement error and therefore shape measurement error. The proposed phase error compensation method is based on our finding that the phase error due to the nonsinusoidal waveform depends only on the nonlinearity of the projector’s gamma. Therefore, if the projector’s gamma is calibrated and the phase error due to the …
Generic Nonsinusoidal Phase Error Correction For Three-Dimensional Shape Measurement Using A Digital Video Projector, Song Zhang, Shing-Tung Yau
Generic Nonsinusoidal Phase Error Correction For Three-Dimensional Shape Measurement Using A Digital Video Projector, Song Zhang, Shing-Tung Yau
Song Zhang
A structured light system using a digital video projector is widely used for 3D shape measurement. However, the nonlinear γ of the projector causes the projected fringe patterns to be nonsinusoidal, which results in phase error and therefore measurement error. It has been shown that, by using a small look-up table (LUT), this type of phase error can be reduced significantly for a three-step phase-shifting algorithm. We prove that this algorithm is generic for any phase-shifting algorithm. Moreover, we propose a new LUT generation method by analyzing the captured fringe image of a flat board directly. Experiments show that this …
Multilevel Quality-Guided Phase Unwrapping Algorithm For Real-Time Three-Dimensional Shape Reconstruction, Song Zhang, Xiaolin Li, Shing-Tung Yau
Multilevel Quality-Guided Phase Unwrapping Algorithm For Real-Time Three-Dimensional Shape Reconstruction, Song Zhang, Xiaolin Li, Shing-Tung Yau
Song Zhang
A multilevel quality-guided phase unwrapping algorithm for real-time 3D shape measurement is presented. The quality map is generated from the gradient of the phase map. Multilevel thresholds are used to unwrap the phase level by level. Within the data points in each level, a fast scan-line algorithm is employed. The processing time of this algorithm is approximately 18.3 ms for an image size of 640×480 pixels in an ordinary computer. We demonstrate that this algorithm can be implemented into our real-time 3D shape measurement system for real-time 3D reconstruction. Experiments show that this algorithm improves the previous scan-line phase unwrapping …
High-Resolution, Real-Time Three-Dimensional Shape Measurement, Song Zhang, Peisen S. Huang
High-Resolution, Real-Time Three-Dimensional Shape Measurement, Song Zhang, Peisen S. Huang
Song Zhang
We describe a high-resolution, real-time 3-D shape measurement system based on a digital fringe projection and phase-shifting technique. It utilizes a single-chip digital light processing projector to project computer-generated fringe patterns onto the object, and a high-speed CCD camera synchronized with the projector to acquire the fringe images at a frame rate of 120frames∕s. A color CCD camera is also used to capture images for texture mapping. Based on a three-step phase-shifting technique, each frame of the 3-D shape is reconstructed using three consecutive fringe images. Therefore the 3-D data acquisition speed of the system is 40frames∕s. With this system, …
Novel Method For Structured Light System Calibration, Song Zhang, Peisen S. Huang
Novel Method For Structured Light System Calibration, Song Zhang, Peisen S. Huang
Song Zhang
System calibration, which usually involves complicated and time-consuming procedures, is crucial for any 3-D shape measurement system. In this work, a novel systematic method is proposed for accurate and quick calibration of a 3-D shape measurement system we developed based on a structured light technique. The key concept is to enable the projector to “capture” images like a camera, thus making the calibration of a projector the same as that of a camera. With this new concept, the calibration of structured light systems becomes essentially the same as the calibration of traditional stereovision systems, which is well established. The calibration …
Generic Nonsinusoidal Phase Error Correction For 3d Shape Measurement Using A Digital Video Projector, Song Zhang, Shing-Tung Yau
Generic Nonsinusoidal Phase Error Correction For 3d Shape Measurement Using A Digital Video Projector, Song Zhang, Shing-Tung Yau
Song Zhang
Structured light system using a digital video projector is increasingly used for a 3-D shape measurement because of its digital nature. However, the nonlinear gamma of the projector causes the projected fringe patterns to be non-sinusoidal, which results in phase error therefore shape measurement error. Previous work showed that, by using a small look-up-table (LUT), this type of phase error can be reduced significantly for a three-step phase-shifting algorithm. In this research, we prove that this type of phase error compensation method is not limited to a three-step phase-shifting algorithm. It is generic for any phase-shifting algorithm. The phase error …
High-Resolution Real-Time 3d Absolute Coordinates Measurement Using A Fast Three-Step Phase-Shifting Algorithm, Song Zhang, Dale Royer, Shing-Tung Yau
High-Resolution Real-Time 3d Absolute Coordinates Measurement Using A Fast Three-Step Phase-Shifting Algorithm, Song Zhang, Dale Royer, Shing-Tung Yau
Song Zhang
High-resolution, real-time 3-D absolute coordinate measurement is highly important in many fields. This paper presents such a system that measures 3-D absolute geometric shapes and positions at 30 frames per second (fps), with an image resolution of 532 × 500. The system is based on a digital fringe projection and fast three-step phase-shifting method. It utilizes a digital-light-processing (DLP) projector to project color encoded computer generated phase-shifted fringe patterns in grayscale, a high-speed CCD camera synchronized with the projector to capture fringe images at 90 fps. Based on the three-step phase-shifting algorithm, any successive three fringe images can be used …
Trapezoidal Phase-Shifting Method For Three-Dimensional Shape Measurement, Peisen S. Huang, Song Zhang, Fu-Pen Chiang
Trapezoidal Phase-Shifting Method For Three-Dimensional Shape Measurement, Peisen S. Huang, Song Zhang, Fu-Pen Chiang
Song Zhang
We propose a novel structured light method, namely a trapezoidal phase-shifting method, for 3-D shape measurement. This method uses three patterns coded with phase-shifted, trapezoidal-shaped gray levels. The 3-D information of the object is extracted by direct calculation of an intensity ratio. Compared to traditional intensity-ratio-based methods, the vertical or depth resolution is six times better. Also, this new method is significantly less sensitive to the defocusing effect of the captured images, which makes large-depth 3-D shape measurement possible. If compared to sinusoidal phase-shifting methods, the resolution is similar, but the data processing speed is at least 4.5 times faster. …
Fast Three-Step Phase-Shifting Algorithm, Song Zhang, Peisen S. Huang
Fast Three-Step Phase-Shifting Algorithm, Song Zhang, Peisen S. Huang
Song Zhang
We propose a new three-step phase-shifting algorithm, which is much faster than the traditional three-step algorithm. We achieve the speed advantage by using a simple intensity ratio function to replace the arctangent function in the traditional algorithm. The phase error caused by this new algorithm is compensated for by use of a lookup table. Our experimental results show that both the new algorithm and the traditional algorithm generate similar results, but the new algorithm is 3.4 times faster. By implementing this new algorithm in a high-resolution, real-time three-dimensional shape measurement system, we were able to achieve a measurement speed of …
High-Resolution, Real-Time 3d Absolute Coordinate Measurement Based On A Phase-Shifting Method, Song Zhang, Shing-Tung Yau
High-Resolution, Real-Time 3d Absolute Coordinate Measurement Based On A Phase-Shifting Method, Song Zhang, Shing-Tung Yau
Song Zhang
We describe a high-resolution, real-time 3D absolute coordinate measurement system based on a phase-shifting method. It acquires 3D shape at 30 frames per second (fps), with 266K points per frame. A tiny marker is encoded in the projected fringe pattern, and detected by software from the texture image and the gamma map. Absolute 3D coordinates are obtained from the detected marker position and the calibrated system parameters. To demonstrate the performance of the system, we measure a hand moving over a depth distance of approximately 700 mm, and human faces with expressions. Applications of such a system include manufacturing, inspection, …
Gpu-Assisted High-Resolution, Real-Time 3-D Shape Measurement, Song Zhang, Dale Royer, Shing-Tung Yau
Gpu-Assisted High-Resolution, Real-Time 3-D Shape Measurement, Song Zhang, Dale Royer, Shing-Tung Yau
Song Zhang
This paper describes a Graphics Processing Unit (GPU)-assisted real-time three-dimensional shape measurement system. Our experiments demonstrated that the absolute coordinates calculation and rendering speed of a GPU is more than four times faster than that of a dual CPU workstation with the same graphics card. By implementing the GPU into our system, we realized simultaneous absolute coordinate acquisition, reconstruction and display at 30 frames per second with a resolution of approximately 266K points per frame. Moreover, a 2+1 phase-shifting algorithm was employed to alleviate the measurement error caused by motion. Applications of the system include medical imaging, manufacturing, entertainment, and …
A Fast Three-Step Phase-Shifting Algorithm, Peisen S. Huang, Song Zhang
A Fast Three-Step Phase-Shifting Algorithm, Peisen S. Huang, Song Zhang
Song Zhang
We propose a new three-step phase-shifting algorithm, which is much faster than the traditional three-step algorithm. We achieve the speed advantage by using a simple intensity ratio function to replace the arctangent function in the traditional algorithm. The phase error caused by this new algorithm is compensated for by use of a look-up-table (LUT). Our experimental results show that both the new algorithm and the traditional algorithm generate similar results, but the new algorithm is 3.4 times faster. By implementing this new algorithm in a high-resolution, real-time 3D shape measurement system, we were able to achieve a measurement speed of …
3-D Optical Measurement Using Phase Shifting Based Methods, Peisen S. Huang, Song Zhang
3-D Optical Measurement Using Phase Shifting Based Methods, Peisen S. Huang, Song Zhang
Song Zhang
We review some of our most recent works on 3-D shape measurement using the digital fringe projection and phase-shifting method. First, we introduce the measurement principle and phase-shifting algorithms. Then we discuss an effective method for phase error compensation and a novel idea for system calibration. Finally, we describe a 3-D shape measurement system for high-resolution, real-time 3-D shape acquisition, reconstruction and display.
Phase Error Compensation For A 3-D Shape Measurement System Based On The Phase-Shifting Method, Song Zhang, Peisen S. Huang
Phase Error Compensation For A 3-D Shape Measurement System Based On The Phase-Shifting Method, Song Zhang, Peisen S. Huang
Song Zhang
This paper describes a novel phase error compensation method for reducing the measurement error caused by non-sinusoidal waveforms in the phase-shifting method. For 3D shape measurement systems using commercial video projectors, the non-sinusoidal nature of the projected fringe patterns as a result of the nonlinear gamma curve of the projectors causes significant phase measurement error and therefore shape measurement error. The proposed phase error compensation method is based on our finding that the phase error due to the non-sinusoidal waveform of the fringe patterns depends only on the nonlinearity of the projector's gamma curve. Therefore, if the projector's gamma curve …
Trapezoidal Phase-Shifting Method For 3d Shape Measurement, Peisen S. Huang, Song Zhang, Fu-Pen Chiang
Trapezoidal Phase-Shifting Method For 3d Shape Measurement, Peisen S. Huang, Song Zhang, Fu-Pen Chiang
Song Zhang
We propose a novel structured light method, namely trapezoidal phase-shifting method, for 3-D shape measurement. This method uses three patterns coded with phase-shifted, trapezoidal-shaped gray levels. The 3-D information of the object is extracted by direct calculation of an intensity ratio. Theoretical analysis showed that this new method was significantly less sensitive to the defocusing effect of the captured images when compared to the traditional intensity-ratio based methods. This important advantage makes large-depth 3-D shape measurement possible. If compared to the sinusoidal phase-shifting method, the resolution is similar, but the processing speed is at least 4.5 times faster. The feasibility …