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Related Concept Videos

Time and frequency -Domain Interpretation of Phase-lead Control01:24

Time and frequency -Domain Interpretation of Phase-lead Control

180
Phase-lead controllers are commonly used in various control systems to enhance response speed and stability. Adjusting the brightness on a television screen offers a practical example of phase-lead control. When contrast is enhanced, a phase-lead controller is employed. Mathematically, phase-lead control is identified when the first parameter is smaller than the second.
The design of phase-lead control involves the strategic placement of poles and zeros to balance steady-state error and system...
180
Time and frequency -Domain Interpretation of Phase-lag Control01:21

Time and frequency -Domain Interpretation of Phase-lag Control

166
Phase-lag controllers are widely used in control systems to improve stability and reduce steady-state errors. A dimmer switch controlling the brightness of a light bulb serves as a practical example of phase-lag control, gradually adjusting the bulb's brightness. Mathematically, phase-lag control or low-pass filtering is represented when the factor 'a' is less than 1.
Phase-lag controllers do not place a pole at zero, but instead influence the steady-state error by amplifying any...
166

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Related Experiment Video

Updated: Oct 30, 2025

High-resolution, High-speed, Three-dimensional Video Imaging with Digital Fringe Projection Techniques
11:34

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Phase Demodulation Method for Fringe Projection Measurement Based on Improved Variable-Frequency Coded Patterns.

Shanshan Lv1, Mingshun Jiang1, Chenhui Su2

  • 1School of Control Science and Engineering, Shandong University, Jinan 250061, China.

Sensors (Basel, Switzerland)
|July 2, 2021
PubMed
Summary
This summary is machine-generated.

A new phase demodulation method uses dual variable-frequency (VF) coded patterns for accurate 3D surface profiling. This approach effectively resolves 2π jump errors in fringe projection, improving surface measurement precision.

Keywords:
EWPFFTVF coded patternsfringe order decoding

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Area of Science:

  • Optical Metrology
  • 3D Surface Measurement
  • Computational Imaging

Background:

  • Fringe projection is a key 3D measurement technology relying on accurate phase calculation.
  • Existing absolute phase demodulation methods struggle with multiple coded patterns and 2π jump errors.

Purpose of the Study:

  • To propose a novel phase demodulation method to overcome limitations of existing techniques.
  • To improve the accuracy and efficiency of phase calculation in 3D surface profiling.

Main Methods:

  • A new method based on dual variable-frequency (VF) coded patterns for phase demodulation.
  • Splitting effective wrapped phase into complete and incomplete period regions.
  • Decoding fringe orders using VF fringe frequency and continuity, with adaptive FFT sampling.
  • Utilizing fringe order consistency for decoding in incomplete regions.

Main Results:

  • Successfully decoded fringe orders in both complete and incomplete wrapped phase regions.
  • Demonstrated effectiveness in phase demodulation for discontinuous and abrupt objects.
  • Experimental results confirm the proposed method's validity and precision.

Conclusions:

  • The proposed dual VF coded pattern method offers a robust solution for absolute phase demodulation.
  • This technique enhances the accuracy of 3D surface profiling in fringe projection systems.
  • The method is effective for complex object geometries, including those with discontinuities and abrupt changes.