Calibration of underwater fisheye camera with multi-frequency heterodyne technique based on light field

Xie, Liangliang; Zhang, Xu; Tu, Dawei; Li, Chen; Xiao, Guoliang; Zhang, Can; Zhuang, Sufeng

doi:10.1088/1361-6501/aba232

Cited by 7 publications

(3 citation statements)

References 21 publications

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“…Treibitz et al 20 studied the adaptability of the SVP camera model for the underwater camera, that the assumption of a single projection center does not hold when the measurement distance is not within the calibration range. In addition, Xie et al 31,32 removed the refraction distortion by converting the underwater image into an equivalent image taken in the air. But the effect of refraction is nonlinear, the approximating SVP model still brings errors.…”

Section: Underwater Refractive Camera Modelmentioning

confidence: 99%

Refraction calibration of housing parameters for a flat-port underwater camera

Shi

et al. 2022

Opt. Eng.

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In underwater computer vision systems, the camera is usually housed in a watertight case with a glass interface between water and air, which causes the light rays to refract, affecting image formation geometrically. In this paper, we propose an approach to calibrate the housing parameters of a flat-port underwater camera for a reasonable underwater refractive camera model. Our approach is specifically designed to deal with the refraction effect caused by the light traveling in different mediums. In this camera model, the calibrated housing parameters include the distance between the camera and glass interface and the normal of the glass interface in the camera coordinate system. We employ an underwater binocular vision system to calibrate the housing parameters in two steps. First, the distance to the glass interface is estimated by capturing a checkerboard image and computing the distance from the camera center to a known flat plane. Then, the normal of the glass interface is calculated by a multiobjective optimization method using geometric constraints in the underwater binocular stereo system. Extensive experiments have been conducted on our underwater dataset and the results verify the effectiveness of the proposed scheme for underwater camera calibration and three-dimensional measurements.

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Section: Underwater Refractive Camera Modelmentioning

confidence: 99%

Refraction calibration of housing parameters for a flat-port underwater camera

Shi

et al. 2022

Opt. Eng.

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“…i. This experiment uses a multifrequency heterodyne method [34] for system calibration. Three types of sinusoidal fringe input projectors with fringe frequencies meeting the requirements of multifrequency heterodynes are designed by the PC, and the sinusoidal fringe frequencies are 1/70, 1/64, and 1/59.…”

Section: Measurement System Calibrationmentioning

confidence: 99%

Step Surface Profile Measurement Based on Fringe Projection Phase-Shifting Using Selective Sampling

Zhang

Huang

2021

Photonics

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Fringe projection is a non-contact optical method that is widely used in the optical precision measurement of complex stepped surfaces. However, the accuracy of the fringe phase extraction employed has a direct impact on the measurement precision of the surface shape. Where phase-shifting measurement is used, the classical equal step phase extraction algorithm can only be used to measure simple and smooth surfaces, and leads to measurement errors on complex stepped surfaces, which affects the accuracy of the phase extraction. In addition, the iterative process lasts for a long time, resulting in a low efficiency. This paper proposes a step-by-step phase-shifting extraction algorithm based on selective sampling to measure the contour of the stepped surface. Firstly, the fringe pattern is sampled at equal intervals to reduce the iterative calculation time. Finally, the accurate measurement phase is calculated by the alternating iteration method. The phase extraction accuracy and iteration times are compared in experimental measurements between classical iterative algorithms such as four-step phase-shifting algorithms and the variable phase shift phase interpolation algorithm based on selective sampling. It is shown that the variable frequency phase-shifting extraction algorithm based on selective sampling has a shorter operation time, smaller error, and higher accuracy than the traditional iterative algorithm in fringe projection measuring complex stepped surfaces.

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“…Combinations of optical imaging, machine design, motion control and image processing, and machine vision technology have the advantages of non-contact, high accuracy and fast processing, which makes it popular for fine measurement and detection in industry [1][2][3][4][5][6][7][8]. Hu et al measured the thickness and profile of transparent material using a fluorescent stereoscopic microscope [9].…”

Section: Introductionmentioning

confidence: 99%

A method of fine size measurement for telecentricity-based error compensation

Li¹,

Wang²,

Tang³

et al. 2021

Meas. Sci. Technol.

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Focusing on the stable magnification, near zero distortion, and wide field of depth (DoF), the telecentric optical system is well suited for size measurements with a large range of working distances. However, suffering from the telecentricity-based error (TBE), the size measurement is connected with the working distances and imaging position of the image sensor, even within the DoF. Therefore, a model of TBE compensation is established, inspired by the radial distortion model in the camera calibration. With the correction of radial distortion coefficients for different working distances, the TBE is evidently improved. The feasibility of the proposed method is verified both in the theory and experiment. Our results show that the uncertainty of size measurement at different working distances of the DoF is improved obviously after the TBE compensation, which is attractive for fine size measurements in industry.

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Calibration of underwater fisheye camera with multi-frequency heterodyne technique based on light field

Cited by 7 publications

References 21 publications

Refraction calibration of housing parameters for a flat-port underwater camera

Refraction calibration of housing parameters for a flat-port underwater camera

Step Surface Profile Measurement Based on Fringe Projection Phase-Shifting Using Selective Sampling

A method of fine size measurement for telecentricity-based error compensation

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