Position measurement at nanoscale currently raises issues such as making significant compromise between range and resolution or as the difficulty to measure several directions with a single sensor. This paper presents a novel visual method to measure displacements at nanometric scale along two axes. This method allows subpixelic measurement of position by using a pseudo-periodic pattern observed by a regular visual setup. This micrometric pattern corresponds to the intertwining of two perpendicular copies of a single-axis pattern made of two frequency carriers with slightly different periods. It was realized in clean room by photolythography of aluminium on glass. The algorithm is based on a twin-scale principle, itself based on direct phase measurement of periodic grids. Experiments are performed at video rate (30 fps) and show a linearity below 0.16% and a repeatability below 14 nm over an unambiguous range of 221 μm. A resolution below 0.5 nm is demonstrated by the use of 2000 images. The method can be adjusted to different ranges, according to the needs.

https://hal.archives-ouvertes.fr/hal-03427080/document

2D visual micro-position measurement based on intertwined twin-scale patterns

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Optical Methods Of Engineering Analysis

Aimed at the low accuracy problem of shear strain measurement in Moire methods, a two-dimensional (2D) Moire phase analysis method is proposed for full-field deformation measurement with high accuracy. A grid image is first processed by the spatial phase-shifting sampling Moire technique to get the Moire phases in two directions, which are then conjointly analyzed for measuring 2D displacement and strain distributions. The strain especially the shear strain measurement accuracy is remarkably improved, and dynamic deformation is measurable from automatic batch processing of single-shot grid images. As an application, the 2D microscale strain distributions of a titanium alloy were measured, and the crack occurrence location was successfully predicted from strain concentration.

Two-dimensional Moiré phase analysis for accurate strain distribution measurement and application in crack prediction.

Optical full-field strain measurement method from wrapped sampling Moiré phase to minimize the influence of defects and its applications

Microengineering/nanoengineering is an emerging field that enables engineering and scientific discoveries in the microworld. As an effective and powerful tool for automation and manipulation at small scales, precision motion measurement by computer microvision is now broadly accepted and widely used in microengineering/nanoengineering. Unlike other measurement methods, the vision-based techniques can intuitively visualize the measuring process with high interactivity, expansibility, and flexibility. This article aims to comprehensively present a survey of microvision-based motion measurement from the collective experience. Working principles of microvision systems are first introduced and described, where the hardware configuration, model calibration, and motion measurement algorithms are systematically summarized. The characteristics and performances of different microvision-based methods are then analyzed and discussed in terms of measurement resolution, range, degree of freedom, efficiency, and error sources. Recent advances of applications empowered by the developed computer microvision-based methods are also presented. The review can be helpful to researchers who engage in the development of microvision-based techniques and provide the recent state and tendency for the research community of vision-based measurement, manipulation, and automation at microscale/nanoscale.

/pdf/a-review-of-computer-microvision-based-precision-motion-y7cm1fyjql.pdf

A Review of Computer Microvision-Based Precision Motion Measurement: Principles, Characteristics, and Applications

In this study, a novel, fast, and accurate in-plane displacement distribution measurement method is proposed that uses a digital camera and arbitrary repeated patterns based on the moire methodology. The key aspect of this method is the use of phase information of both the fundamental frequency and the high-order frequency components of the moire fringe before and after deformations. Compared with conventional displacement methods and sensors, the main advantages of the method developed herein are its high resolution, accuracy, speed, low cost, and easy implementation. The effectiveness is confirmed by a simple in-plane displacement measurement experiment, and the experimental results indicate that an accuracy of 1/1000 of the pitch can be achieved for various repeated patterns. This method is useful for various applications ranging from the study of displacement and strain distributions in materials science, the biomimetics field, and mechanical material testing, to secure the integrity of infrastructures.

Accurate full-field optical displacement measurement technique using a digital camera and repeated patterns

Imaging based nondestructive monitoring systems are critical for evaluation of large-scale infrastructures. In this study, an accurate and fast in-plane displacement measurement method based imaging technique is developed for the purpose of health monitoring of large-scale infrastructures such as high building, long bridge, etc. The build-in repeated patterns on infrastructure facade, such as tile, checker, and brick wall pattern is used to measure the in-plane displacement distribution accurately. By performing down-sampling and intensity interpolation image processing to the images captured before and after deformations, multiple phase-shifted moire fringe can be obtained simultaneously. The phase distribution of the moire fringe is calculated using the phase shifting method and discrete Fourier transform technique. In the present study, both the fundamental and high frequency components are considered to analyze the repeated patterns. The in-plane displacement distribution can be obtained from the phase differences of the moire fringe before and after deformations. Compared with conventional displacement methods and sensors, the main advantages of the method developed herein are high-resolution, accurate, fast, low-cost, and easy to implement. The principle of the proposed inplane displacement measurement is presented. The effectiveness of our method is confirmed by a simple displacement measurement experiment. Experimental result showed that a sub-millimeter displacement could be successfully detected for the field of view with meter-scale.

Accurate and fast in-plane displacement measurement method for large-scale structures by utilizing repeated pattern

https://www.jstage.jst.go.jp/article/jjsem/14/4/14_244/_pdf

Full-field Displacement Measurement Method for Large-scale Structures by Using Tile Patterns

This paper presents an experimental technique for measuring displacement distribution from an image of repeated patterns and JPEG compressed images. The measurement accuracy of the developed method is insusceptible to the degree of JPEG compression because only lower spatial frequency components of the repeated pattern are used to calculate the displacement distribution, and high spatial frequency components have high priority to cut-off according to the JPEG compression algorithm. The insensitivity to the JPEG compression was confirmed by a displacement measurement using JPEG images of various compression ratios or image qualities. We found that by using the highest quality JPEG image, the accuracy of displacement measurement could research 1/1000 of the repeated pattern pitch, as same the uncompressed BMP images. In addition, displacement with accuracy of 1/500 pitch could be measured from a compressed JPEG image of which the file size was 1/50 of that of the BMP image. This technique is useful for measurement using a high-speed camera with high-resolution digital images for a long-term or wireless image transfer.

/pdf/full-field-displacement-measurement-technique-by-using-25eyaqvd77.pdf

Satoshi Hayashi

Papers

Accurate full-field optical displacement measurement technique using a digital camera and repeated patterns

Accurate and fast in-plane displacement measurement method for large-scale structures by utilizing repeated pattern

Full-field Displacement Measurement Method for Large-scale Structures by Using Tile Patterns

Full-Field Displacement Measurement Technique by Using Repeated Patterns and JPEG Compressed Images