Coordinate calculation for direct shape measurement based on optical flow

Sun, Ping; Dai, Qing; Tang, Yuxin; Lei, Zhifang

doi:10.1364/ao.59.000092

Cited by 4 publications

(5 citation statements)

References 18 publications

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“…The mean value of the maxima in Figure 3b is 52.39 pixels and the corresponding tilt angle α = 0.1498 rad ≈ 8.586 • , which is consistent with the theoretical values (52.47 pixels, 8.599 • ). Since the optical flow (OF) algorithm is a mature method for in-plane displacement measurement [6,9], for comparison, the simulated result by the Horn-Schunck (HS)-OF method [6] is shown in Figure 3c. Figure 3d shows the cross-section data comparison of Figure 3a-c in the y direction at x = 174 for further analysis.…”

Section: Simulated Results and Analysismentioning

confidence: 99%

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Correlation-Based Out-of-Plane Displacement Measurement for Optical Fiber Material

Zhao

Sun

et al. 2021

Photonics

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Due to the monitoring requirement of optical fiber industrial production, an out-of-plane displacement measurement method is proposed. Firstly, the in-plane displacements between two consecutive images, captured through a microscope with a CCD camera, are estimated by the Digital Speckle Correlation Method (DSCM). Subsequently, the out-of-plane displacement of optical fiber material can be obtained by the wedge model. Finally, the effectiveness of the method is verified experimentally by comparing the measurement data of routine practice with its theoretical values. Simulation and experimental results indicate that the absolute errors and the relative errors of the measurement by the optical microscope with a magnification of 50× are less than ±0.2 μm and 5%, respectively. The new method only needs two images obtained by the microscopic imaging system with a single camera to accomplish the measurement, which can significantly reduce the measurement time and complexity of the arrangement. Further, the method needs neither frequency domain conversion nor phase unwrapping operation, therefore, it is especially suitable for dynamic out-of-plane displacement measurement. The proposed method has been applied to the industrial uniformity and micro–nano-scale deformation monitoring of optical fiber image transmission materials.

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Section: Simulated Results and Analysismentioning

confidence: 99%

“…Currently, there exist many out-of-plane displacement measurement methods, based mainly on laser spot scanning [5], interferometry [6,7], and fringe projection techniques [8,9]. However, due to the constraints of the detecting conditions, these methods cannot work perfectly in these applications.…”

Section: Introductionmentioning

confidence: 99%

Correlation-Based Out-of-Plane Displacement Measurement for Optical Fiber Material

Zhao

Sun

et al. 2021

Photonics

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“…Although only two images are used for projector calibration, all pixels in the captured images can be used as effective information points, by which the projector calibration is of high accuracy. By using the calibrated coordinates of the camera and the projector, the height distribution of a measured object can be obtained efficiently [23,24].…”

Section: Principle Of Projector Calibrationmentioning

confidence: 99%

“…The optical flow method is widely used to obtain the motion information of moving objects with the advantages of simple operation and strong robustness to noise [20][21][22]. When utilizing it to retrieve the height distribution of an object, the information of the measured surface shape can be obtained directly only using one deformed fringe pattern without phase-to-height operation [23,24].…”

Section: Introductionmentioning

confidence: 99%

Rapid Calibration of the Projector in Structured Light Systems Based on Brox Optical Flow Estimation

et al. 2022

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In this work, we propose a rapid calibration technique for locating the projector in the structured light measurement system. Using Brox optical flow, the calibration of the three-dimensional (3-D) coordinates of the projector only requires two images captured before and after the motion of the calibration plate. The calibration principle presented in geometry depicts the relation between the position of the projector, the camera, and the optical flow caused by the movement of the calibration plate. Some important influences on accuracy are discussed, such as the environmental noises and the localization error of the camera and the calibration plate, illustrated by numerical simulations. The simulation results show that the relative errors of the projector calibration results are less than 0.8% and 1% in the case of the calibration images polluted by Gaussian noise of SNR of 40 dB and 20 dB, respectively. An actual experiment measured a square standard block, and a circular thin plate verifies the proposed method’s feasibility and practicality. The results show that the height distributions of the two specimens are in good agreement with their true values, and the maximum absolute errors are 0.1 mm and 0.08 mm, respectively.

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“…Different from traditional phase measurement techniques, the optical flow surface shape measurement technique does not measure the phase distribution but the height distribution directly, only requiring two frames before and after deformation. The measurement accuracy of it is equivalent to that of the FTP method [9]. Because the height distribution is calculated point-by-point, the optical flow method is robust to noises [10].…”

Section: Introductionmentioning

confidence: 99%

Object Shape Measurement Based on Brox Optical Flow Estimation and Its Correction Method

et al. 2020

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In this work, a new method of measuring surface shape based on Brox optical flow estimation is presented. The measuring system consists of a projector, a measured object and a charge coupled device (CCD) camera. The grating fringes are projected onto the reference plane at a small angle. Two fringe images—before and after placing the measured object on the reference plane—are captured, respectively. Then, the optical flow field between two images is evaluated by using Brox optical flow algorithm. The theoretical relationship between the optical flow field and the height of the measured surface is established. According to the relationship, the height distribution of the measured object can be retrieved quickly without phase-to-height transformation. However, the calculated height distribution has been found to be deviated from its true value. To solve the problem, a correction scheme suitable for the optical flow method is proposed. By using the correction scheme, the accuracy of the calculated result is greatly improved. Simulations and experiments are completed to verify the feasibility of the proposed method and the accuracy of the correction method. The results show that the proposed method is more accurate than that of the Fourier transform method. Compared with traditional surface shape measurement, the optical flow method has some obvious advantages: (1) Only two frame images are required to recover the height distribution. (2) Relatively simple in measurement process and calculation so less time consuming. (3) Because the optical flow method contains time factor itself, it is more suitable for dynamic measurement. (4) No restrictions on projection pattern.

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Coordinate calculation for direct shape measurement based on optical flow

Cited by 4 publications

References 18 publications

Correlation-Based Out-of-Plane Displacement Measurement for Optical Fiber Material

Correlation-Based Out-of-Plane Displacement Measurement for Optical Fiber Material

Rapid Calibration of the Projector in Structured Light Systems Based on Brox Optical Flow Estimation

Object Shape Measurement Based on Brox Optical Flow Estimation and Its Correction Method

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