6 results about "Fringe pattern" patented technology

The application discloses a digital phase-shifting phase recovery method of ESPI fringe pattern based on distance mapping, which comprises the following steps: 1) extracting the direction of each pixel point of the fringe pattern, and then calculating the normal curve of the fringe according to the fringe direction to obtain the moving direction of the fringe; 2) extracting the center line of the dark fringe, calculating the width of the fringe according to the center line of the fringe, and obtaining the moving distance of the fringe through distance mapping; 3) comprehensively moving the direction and the distance, and performing digital phase-shifting on the initial fringe pattern point by point, and adopting the bilinear gray interpolation to obtain the fringe pattern after digital phase-shifting; 4) calculating the wrapped phase corresponding to the fringe pattern; and 5) performing unwrapping processing on the wrapped phase to recover the full-field phase of the fringe pattern. The application extracts the phase through the digital image processing technology on the single fringe pattern, avoids the problem of inaccurate phase-shifting existing in the traditional physical phase-shifting technology in dynamic measurement, and can effectively improve the accuracy of the phase recovery of the single fringe pattern.

This invention discloses a phase-height mapping calibration method and apparatus in fringe projection, relating to the field of three-dimensional object contour measurement technology. The method includes: controlling a projector to project a set of phase-shifted sinusoidal fringe patterns onto a micromirror array with known height values; simultaneously triggering a camera to acquire fringe image sequences; performing phase shift calculations on the fringe image sequences to obtain a wrap-around phase map; constructing a global optimization model of absolute phase using the known height value of the micromirror array as an absolute constraint; solving for the absolute phase field corresponding to the height of the micromirror array; extracting the center coordinates, absolute phase values, and known height values ​​of each micromirror element; constructing a three-dimensional control point set; fitting the three-dimensional control point set; calculating the continuous model coefficient field; and forming a phase-height lookup table. This invention can significantly improve the real-time calculation efficiency of three-dimensional measurement, meeting the practical needs of high-precision, high-stability industrial three-dimensional shape measurement.

The present invention is to solve the problem that the deformation of the workpiece surface can be automatically determined without the reference shape data of the workpiece. In order to solve the above problem, a workpiece quality determination system determines the quality of a workpiece based on a fringe pattern projected onto the workpiece surface, and includes: an observation angle setting section that sets an observation angle for observing a projected fringe pattern projected onto the workpiece; a fringe projection angle setting section that sets a fringe projection angle of the projected fringe pattern at the set observation angle; a reference fringe creating section that creates a reference fringe pattern based on the projected fringe pattern at the set fringe projection angle; and a quality determination section that calculates a difference between the projected fringe pattern and the reference fringe pattern at the fringe projection angle, and performs quality determination based on the difference.

There is provided a hologram quality assessment method. The quality assessment method according to an embodiment may receive an input of an original holographic fringe pattern and a target holographic fringe pattern which is a comparison target, may calculate angular spectra of the inputted original holographic fringe pattern and target holographic fringe pattern, respectively, and may calculate a PSNR as a quality value of the target holographic fringe pattern from the calculated angular spectra. Since the angular spectrum of the holographic fringe pattern has the same characteristic without a change according to a distance, not only a diffraction wavefront that is positioned at a position of the holographic fringe pattern but also a diffraction wavefront positioned at a certain distance may have the same PSNR value. Accordingly, objective quality assessment for a holographic fringe pattern is possible.

A three-dimensional shape measurement device includes: a projector to project a fringe pattern; multiple cameras having a measurable working distance range, respectively; and a processing circuitry to analyze the fringe pattern captured by the multiple cameras, using a phase shift method, to acquire three-dimensional information of an object. The multiple cameras are all arranged on one side of the projector. A projector optical axis of the projector and camera optical axes of the multiple cameras are arranged in the same plane. The camera optical axes are arranged such that interior angles between the camera optical axes and the projector optical axis are different from each other.

A defect detection system includes a light source configured to project a fringe pattern onto a surface. The fringe pattern includes a ratio of dark portions to light portions of at least 1.5 and a fringe pattern having a period of at least 1 millimeter. The defect detection system further includes an image capturing device configured to capture an image of the projected fringe pattern. The defect detection system further includes a movement mechanism configured to move the image capturing device at an angle of between 30° and 90°, measured from perpendicular to the surface. The defect detection system further includes an image analyzer configured to detect a defect on the surface, based on the captured image. The defect detection system further includes a defect characterizer configured to provide a defect characteristic. The defect detection system further includes a communication component configured to report the defect characteristic.