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Lv Z, Zhu K, He X, Zhang L, He J, Mu Z, Wang J, Zhang X, Hao R. Phase Unwrapping Error Correction Based on Multiple Linear Regression Analysis. SENSORS (BASEL, SWITZERLAND) 2023; 23:2743. [PMID: 36904946 PMCID: PMC10007165 DOI: 10.3390/s23052743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 02/23/2023] [Accepted: 02/23/2023] [Indexed: 06/18/2023]
Abstract
Fringe projection profilometry (FPP) is prone to phase unwrapping error (PUE) due to phase noise and measurement conditions. Most of the existing PUE-correction methods detect and correct PUE on a pixel-by-pixel or partitioned block basis and do not make full use of the correlation of all information in the unwrapped phase map. In this study, a new method for detecting and correcting PUE is proposed. First, according to the low rank of the unwrapped phase map, multiple linear regression analysis is used to obtain the regression plane of the unwrapped phase, and thick PUE positions are marked on the basis of the tolerance set according to the regression plane. Then, an improved median filter is used to mark random PUE positions and finally correct marked PUE. Experimental results show that the proposed method is effective and robust. In addition, this method is progressive in the treatment of highly abrupt or discontinuous regions.
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Affiliation(s)
- Zhuang Lv
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
| | - Kaifeng Zhu
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xin He
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
| | - Lei Zhang
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
| | - Jiawei He
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
| | - Zhiya Mu
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
| | - Jun Wang
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
| | - Xin Zhang
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
| | - Ruidong Hao
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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Liu J, Tian P, Li H, Wei H, Deng G, Zhou S, Ma Z, Wang W, He L. An Improved Synthesis Phase Unwrapping Method Based on Three-Frequency Heterodyne. SENSORS (BASEL, SWITZERLAND) 2022; 22:9388. [PMID: 36502089 PMCID: PMC9738266 DOI: 10.3390/s22239388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 11/14/2022] [Accepted: 11/30/2022] [Indexed: 06/17/2023]
Abstract
An improved three-frequency heterodyne synthesis phase unwrapping method is proposed to improve the measurement accuracy through phase difference and phase sum operations. This method can reduce the effect of noise and increase the equivalent phase frequency. According to the distribution found in the phase difference calculation process, the Otsu segmentation is introduced to judge the phase threshold. The equivalent frequency obtained from the phase sum is more than those of all projected fringe patterns. In addition, the appropriate period combinations are also studied. The simulations and related experiments demonstrate the feasibility of the proposed method and the ability to improve the accuracy of the measurement results further.
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Affiliation(s)
- Jiangtao Liu
- College of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China
| | - Peng Tian
- School of Mechanical Engineering, Sichuan University, Chengdu 610065, China
| | - Hongru Li
- College of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China
| | - Hao Wei
- College of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China
| | - Guoliang Deng
- College of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China
| | - Shouhuan Zhou
- College of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China
| | - Zeyu Ma
- School of Mechanical Engineering, Sichuan University, Chengdu 610065, China
| | - Wenwu Wang
- School of Mechanical Engineering, Sichuan University, Chengdu 610065, China
| | - Liang He
- School of Mechanical Engineering, Sichuan University, Chengdu 610065, China
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Li J, Guan J, Wang Y, Chen X, Xi J. Accurate estimation of camera response function for high dynamic range measurement. APPLIED OPTICS 2022; 61:167-176. [PMID: 35200816 DOI: 10.1364/ao.440744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 11/15/2021] [Indexed: 06/14/2023]
Abstract
A high dynamic range surface has large reflectivity variations and measuring it with a structured light technique could cause pixel saturation that will seriously degrade the measurement accuracy. Accurate identification of saturated pixels will significantly improve the measurement accuracy. This paper introduces an accurate estimation approach to the camera response function (CRF) for high dynamic range measurement and proposes a method that uses the estimated CRF to identify the saturated pixels in captured images. We perform experiments using the proposed saturation identification method and the other existing methods to compare both the saturation identification accuracy and measurement accuracy. The experiment results verify both the accuracy and suitability of the proposed method.
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Phase Demodulation Method for Fringe Projection Measurement Based on Improved Variable-Frequency Coded Patterns. SENSORS 2021; 21:s21134463. [PMID: 34210041 PMCID: PMC8271525 DOI: 10.3390/s21134463] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Revised: 06/19/2021] [Accepted: 06/24/2021] [Indexed: 11/16/2022]
Abstract
The phase-to-height imaging model, as a three-dimensional (3D) measurement technology, has been commonly applied in fringe projection to assist surface profile measurement, where the efficient and accurate calculation of phase plays a critical role in precise imaging. To deal with multiple extra coded patterns and 2π jump error caused to the existing absolute phase demodulation methods, a novel method of phase demodulation is proposed based on dual variable-frequency (VF) coded patterns. In this paper, the frequency of coded fringe is defined as the number of coded fringes within a single sinusoidal fringe period. First, the effective wrapped phase (EWP) as calculated using the four-step phase shifting method was split into the wrapped phase region with complete period and the wrapped phase region without complete period. Second, the fringe orders in wrapped phase region with complete period were decoded according to the frequency of the VF coded fringes and the continuous characteristic of the fringe order. Notably, the sampling frequency of fast Fourier transform (FFT) was determined by the length of the decoding interval and can be adjusted automatically with the variation in height of the object. Third, the fringe orders in wrapped phase region without complete period were decoded depending on the consistency of fringe orders in the connected region of wrapped phase. Last, phase demodulation was performed. The experimental results were obtained to confirm the effectiveness of the proposed method in the phase demodulation of both discontinuous objects and highly abrupt objects.
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