Calibration of a Dual-Telecentric Fringe Projection System Using a Planar Calibration Target

Fringe projection technologies have been widely used for three-dimensional (3D) shape measurement. One of the critical issues is absolute phase recovery, especially for measuring multiple isolated objects. This paper proposes a method for absolute phase retrieval using only one coded pattern. A total of four patterns including one coded pattern and three phase-shift patterns are projected, captured, and processed. The wrapped phase, as well as average intensity and intensity modulation, are calculated from three phase-shift patterns. A code word encrypted into the coded pattern can be calculated using the average intensity and intensity modulation. Based on geometric constraints of fringe projection system, the minimum fringe order map can be created, upon which the fringe order can be calculated from the code word. Compared with the conventional method, the measurement depth range is significantly improved. Finally, the wrapped phase can be unwrapped for absolute phase map. Since only four patterns are required, the proposed method is suitable for real-time measurement. Simulations and experiments have been conducted, and their results have verified the proposed method.

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Single image geometry inspection using inverse endoscopic fringe projection

ACTA IMEKO ◽

10.21014/acta_imeko.v4i2.186 ◽

2015 ◽

Vol 4 (2) ◽

pp. 4 ◽

Cited By ~ 2

Author(s):

Steffen Matthias ◽

Christoph Ohrt ◽

Andreas Pösch ◽

Markus Kästner ◽

Eduard Reithmeier

Keyword(s):

Phase Measurement ◽

Measurement Techniques ◽

Measuring Method ◽

Pattern Generation ◽

Fringe Projection ◽

Free Form ◽

Projection System ◽

New Device ◽

Early Results ◽

Geometry Inspection

Fringe projection is an important technology for the measurement of free form elements in several application fields. It can be applied for geometry elements smaller than one millimeter. In combination with deviation analysis algorithms, errors in fabrication lines can be found promptly to minimize rejections. However, some fields cannot be covered by the classical fringe projection approach. Due to shadowing, filigree form elements on narrow or internal carrier geometries cannot be captured. To overcome this limitation, a fiberscopic micro fringe projection sensor was developed. The new device is capable of resolutions of less than 15 µm with uncertainties of about 35 µm in a workspace of 3 × 3 × 3 mm³.<br />Using standard phase measurement techniques, such as Gray-code and cos²-patterns, measurement times of over a second are too high for in-situ operation. The following work will introduce a new approach of applying a new one image measuring method to the fiberscopic system, based on inverse fringe projection. The fiberscopic fringe projection system employs a laser light source in combination with a digital micro-mirror device (DMD) to generate fringe patterns. Fiber optical image bundles (FOIB) are used in combination with gradient-index lenses to project these patterns on the specimen. This advanced optical system creates high demands on the pattern generation algorithms to generate exact inverse patterns for arbitrary CAD-modelled geometries. Approaches of the optical simulations in the context of the complex beam path, together the drawbacks of the limited resolutions of the FOIBs shall be discussed. Early results of inverse pattern simulations using a ray tracing approach of a pinhole system model are presented.<br />

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Single-shot 3D shape measurement of discontinuous objects based on a coaxial fringe projection system

Applied Optics ◽

10.1364/ao.58.00a169 ◽

2019 ◽

Vol 58 (5) ◽

pp. A169 ◽

Cited By ~ 19

Author(s):

Zhangying Wang ◽

Zonghua Zhang ◽

Nan Gao ◽

Yanjun Xiao ◽

Feng Gao ◽

...

Keyword(s):

Fringe Projection ◽

Shape Measurement ◽

Single Shot ◽

Projection System ◽

3D Shape ◽

3D Shape Measurement

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Feasibility of Using Fringe Projection System for Corrosion Monitoring in Metals of Interest in Cultural Heritage

Advancement of Optical Methods in Experimental Mechanics, Volume 3 - Conference Proceedings of the Society for Experimental Mechanics Series ◽

10.1007/978-3-319-63028-1_18 ◽

2017 ◽

pp. 111-118 ◽

Cited By ~ 1

Author(s):

C. Casavola ◽

P. Pappalardi ◽

G. Pappalettera ◽

G. Renna

Keyword(s):

Cultural Heritage ◽

Fringe Projection ◽

Corrosion Monitoring ◽

Projection System

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Systematic bias compensation for a moire fringe projection system

10.1117/12.614564 ◽

2005 ◽

Author(s):

D. Purcell ◽

A. Samara ◽

A. Davies ◽

F. Farahi

Keyword(s):

Fringe Projection ◽

Systematic Bias ◽

Projection System ◽

Moire Fringe ◽

Moiré Fringe ◽

Bias Compensation

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Uniaxial High-Speed Micro-Scale Three-Dimensional Surface Topographical Measurements Using Fringe Projection

Journal of Micro and Nano-Manufacturing ◽

10.1115/1.4049363 ◽

2020 ◽

Author(s):

Yi Zheng ◽

Beiwen Li

Keyword(s):

High Speed ◽

Sample Surface ◽

3D Scanning ◽

In Situ Monitoring ◽

Fringe Projection ◽

Depth Information ◽

Projection Technique ◽

Projection System ◽

Loop Control

Abstract In-situ inspection has drawn many attentions in manufacturing due to the importance of quality assurance. Having an accurate and robust in-situ monitoring can assist corrective actions for a closed-loop control of a manufacturing process. The fringe projection technique, as a variation of the structured light technique, has demonstrated significant potential for real-time in-situ monitoring and inspection given its merits of conducting simultaneous high-speed and high accuracy measurements. However, high-speed 3D scanning methods like fringe projection technique are typically based on triangulation principle, meaning that the depth information is retrieved by analyzing the triangulation relationship between the light emitter (i.e., projector), the image receiver (i.e., camera) and the tested sample surface. Such measurement scheme cannot reconstruct 3D surfaces where large geometrical variations are present, such as a deep-hole or a stair geometry. This is because large geometrical variations will block the auxiliary light used in the triangulation based methods, which will resultantly cause a shadowed area to occur. In this paper, we propose a uniaxial fringe projection technique to address such limitation. We measured a stair model using both conventional triangulation-based fringe projection technique and the proposed method for comparison. Our experiment demonstrates that the proposed uniaxial fringe projection technique can perform high-speed 3D scanning without shadows appearing in the scene. Quantitative testing shows that an accuracy of 1.15% can be obtained using the proposed uniaxial fringe projection system.

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