Pixelwise Phase Unwrapping Based on Ordered Periods Phase Shift

Abstract

The existing phase-shift methods are effective in achieving high-speed, high-precision, high-resolution, real-time shape measurement of moving objects; however, a phase-unwrapping method that can handle the motion of target objects in a real environment and is robust against global illumination as well is yet to be established. Accordingly, a robust and highly accurate method for determining the absolute phase, using a minimum of three steps, is proposed in this study. In this proposed method, an order structure that rearranges the projection pattern for each period of the sine wave is introduced, so that solving the phase unwrapping problem comes down to calculating the pattern order. Using simulation experiments, it has been confirmed that the proposed method can be used in high-speed, high-precision, high-resolution, three-dimensional shape measurements even in situations with high-speed moving objects and presence of global illumination. In this study, an experimental measurement system was configured with a high-speed camera and projector, and real-time measurements were performed with a processing time of 1.05 ms and a throughput of 500 fps.

Instability Compensation of Recording Interferometer in Phase-Sensitive OTDR

“…To obtain the absolute value of the phase change, the use of phase unwrapping methods is required [ 60 , 61 , 62 , 63 ]. For a 3 × 3 MZI, the phase difference between adjacent outputs is , and having the signals from at least two of the three available photoreceivers, one can calculate the phase change, in the φ-OTDR sensor, by using the following formulas [ 51 ]: where …”

“…The problem of wrong phase unwrapping when crossing the 2π value is cumulative in nature, and, as will be shown further, it can significantly affect the final result, especially during long-term measurements. As given in [ 51 ], it is possible to unwrap the phase using the three PDs amplitude signals by the following formula: which does not involve signal derivatives.…”

“…In addition to detecting the happening of an event acting on the optical fiber—for example unauthorized work in telecommunication wells [ 41 ] and in a number of other tasks, such as measuring oil well parameters [ 38 , 39 , 48 , 49 , 50 ]—it is necessary to quantitatively detect the absolute value of the phase change. This requires unwrapping the phase signal [ 51 ] and obtaining an analog-and-continuous measurement of the phase without 2π phase jumps.…”

Application of Hybrid Intelligent Multi-Objective Lighting Algorithms in Housing Design, 1-6.

“…Bae et al [9] proposed a new method for detecting photoelectrochemical reactions on semiconductor surfaces using the global illumination, which solved the problem of poor detection performance of electrochemical microscopy on semiconductor surfaces. Tabata et al [10] proposed a phase unwrapping method to handle the motion of target objects in real environments. This method was robust to global illumination and could project high-speed moving objects with high accuracy and resolution.…”

Dynamic 3D Measurement without Motion Artifacts Based on Feature Compensation

“…Nonetheless, this approach may result in phase ambiguity due to the periodicity of the sinusoidal signal [ 24 ]. One possible solution is to utilize the time phase unwrapping (TPU) algorithm with auxiliary patterns such as Gray codes or multi-wavelength fringe [ 25 , 26 ]. Another approach is the use of composite phase-shifting schemes like dual-frequency PSP, which can resolve phase ambiguity without significantly increasing the number of patterns.…”