Accuracy assessment of fringe projection profilometry and digital image correlation techniques for three-dimensional shape measurements

Abstract

With ever-increasing demand for three-dimensional (3D) imaging and shape measurements in a variety of fields, measurement accuracy has become of vital importance to numerous scientific and engineering applications. This paper presents an experimental investigation into the accuracy comparison of two prevalent 3D imaging and shape measurement methods: fringe projection profilometry (FPP) and 3D digital image correlation (3D-DIC) techniques. A detailed description of their principles reveals their inherent similarities and fundamental differences. A measurement system composed of both techniques is employed in the study, and a test target with speckle checkerboard patterns on its surface is adopted to allow simultaneous FPP and 3D-DIC measurements. The evaluation puts emphasis on how the geometric angles between key hardware components affect the 3D measurement accuracy. Experiments show that the depth and height measurements of both techniques can reach sub-micron accuracy, and the relative accuracy of the 3D shape or position measurements can reach 1/600 000.

Effect of System Parameters on Phase Error of Focus-Free Digital Fringe Projection Profilometry System

“…As the distance between the object surface and (camera and projector) increases the camera field of view increases causing the object to be represented by a smaller number of pixels in x and y direction. Also, when fringes of the same period are used at all distances the value of phase shift due to the object height decreases as the distance increases as listed in table (3). Figure (14) shows the phase shift map at each distance.…”

“…Fringe images were captured by the camera then, phase was calculated using equation ( 5) and unwrapped to remove 2π discontinuities. phase error is calculated at each distance and listed in table (3). Figure (12) shows phase error of 500 th row of the unwrapped phase map associated with distances.…”

“…Three-dimensional (3D) measurements have various applications in different fields such as biomedical engineering, machine vision, medical practice, reserve engineering, quality assurance, biometric security, and entertainment [1][2][3] . 3D shape could be retrieved using contact techniques such as Coordinate Measuring Machine (CMM).…”

“…These techniques are limited by slow performance, obligation of touching the measured object and high cost. Non-contact techniques such as time-of-flight (TOF) method, interferometry method, Digital Fringe projection profilometry (DFPP), and laser scanning method have the advantage of overcoming the previous limitations [3,4] . DFPP is one of the most used noncontact techniques for 3D imaging [5] due to its speed, accuracy, and flexibility [6][7][8][9] .…”

“…Performance of DFPP system is characterized by many factors such as resolution, speed and the most important factor is accuracy. The accuracy is affected by several factors such as system components, system calibration, geometric and surface characteristics of tested object, system set up and ambient illumination [3] .…”