scholarly journals Autofocusing method for a digital fringe projection system with dual projectors

2020 ◽  
Vol 28 (9) ◽  
pp. 12609 ◽  
Author(s):  
Min Zhong ◽  
Xiaowei Hu ◽  
Feng Chen ◽  
Chao Xiao ◽  
Duan Peng ◽  
...  
Keyword(s):  
Fringe Projection ◽  
Projection System ◽  
Digital Fringe Projection

scholarly journals Flexible Digital Fringe Projection System for Step-height Measurement

2010 ◽  
Author(s):  
Song Zhang ◽  
James Oliver ◽  
Pramod K. Rastogi ◽  
Erwin Hack
Keyword(s):  
Step Height ◽  
Fringe Projection ◽  
Height Measurement ◽  
Projection System ◽  
Digital Fringe Projection

scholarly journals Absolute Phase Retrieval Using One Coded Pattern and Geometric Constraints of Fringe Projection System

2018 ◽  
Vol 8 (12) ◽  
pp. 2673 ◽  
Author(s):  
Xu Yang ◽  
Chunnian Zeng ◽  
Jie Luo ◽  
Yu Lei ◽  
Bo Tao ◽  
...  
Keyword(s):  
Phase Shift ◽  
Phase Retrieval ◽  
Code Word ◽  
Geometric Constraints ◽  
Fringe Projection ◽  
Average Intensity ◽  
Fringe Order ◽  
Projection System ◽  
Absolute Phase ◽  
Three Phase

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.

Dynamics range enhancement in digital fringe projection technique

2015 ◽  
Vol 39 ◽  
pp. 243-251 ◽  
Author(s):  
Gelareh Babaie ◽  
Mehrdad Abolbashari ◽  
Faramarz Farahi
Keyword(s):  
Fringe Projection ◽  
Projection Technique ◽  
Digital Fringe Projection

scholarly journals Single image geometry inspection using inverse endoscopic fringe projection

ACTA IMEKO ◽  
2015 ◽  
Vol 4 (2) ◽  
pp. 4 ◽  
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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