3 Speckle photography and speckle interferometry

In the concept of the process signature, the relationship between a material load and the modification remaining in the workpiece is used to better understand and optimize manufacturing processes. The basic prerequisite for this is to be able to measure the loads occurring during the machining process in the form of mechanical deformations. Speckle photography is suitable for this in-process measurement task and is already used in a variety of ways for in-plane deformation measurements. The shortcoming of this fast and robust measurement technique based on image correlation techniques is that out-of-plane deformations in the direction of the measurement system cannot be detected and increases the measurement error of in-plane deformations. In this paper, we investigate a method that infers local out-of-plane motions of the workpiece surface from the decorrelation of speckle patterns and is thus able to reconstruct three-dimensional deformation fields. The implementation of the evaluation method enables a fast reconstruction of 3D deformation fields, so that the in-process capability remains given. First measurements in a deep rolling process show that dynamic deformations underneath the die can be captured and demonstrate the suitability of the speckle method for manufacturing process analysis.

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Development of a Compound Speckle Interferometer for Precision Three-Degree-of-Freedom Displacement Measurement

Sensors ◽

10.3390/s21051828 ◽

2021 ◽

Vol 21 (5) ◽

pp. 1828

Author(s):

Hung-Lin Hsieh ◽

Bo-Yen Sun

Keyword(s):

Speckle Interferometry ◽

Degree Of Freedom ◽

Heterodyne Interferometry ◽

Beam Splitting ◽

Speckle Interferometer ◽

Real World Applications ◽

Three Degree Of Freedom ◽

Contact Displacement ◽

Displacement Measurements ◽

Measurement Capabilities

In this study, a compound speckle interferometer for measuring three-degree-of-freedom (3-DOF) displacement is proposed. The system, which combines heterodyne interferometry, speckle interferometry and beam splitting techniques, can perform precision 3-DOF displacement measurements, while still having the advantages of high resolution and a relatively simple configuration. The incorporation of speckle interferometry allows for non-contact displacement measurements by detecting the phase of the speckle interference pattern formed from the convergence of laser beams on the measured rough surface. Experiments were conducted to verify the measurement capabilities of the system, and the results show that the proposed system has excellent measurement capabilities suitable for future real-world applications.

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Microshape Measurement Method Using Speckle Interferometry Based on Phase Analysis

Photonics ◽

10.3390/photonics8040112 ◽

2021 ◽

Vol 8 (4) ◽

pp. 112

Author(s):

Yasuhiko Arai

Keyword(s):

Fine Structure ◽

Phase Analysis ◽

Measurement Method ◽

Phase Distribution ◽

Periodic Structures ◽

Scattered Light ◽

Speckle Interferometry ◽

Diffraction Limit ◽

Silica Microspheres ◽

Measured Object

A method for the measurement of the shape of a fine structure beyond the diffraction limit based on speckle interferometry has been reported. In this paper, the mechanism for measuring the shape of the fine structure in speckle interferometry using scattered light as the illumination light is discussed. Furthermore, by analyzing the phase distribution of the scattered light from the surface of the measured object, this method can be used to measure the shapes of periodic structures and single silica microspheres beyond the diffraction limit.

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A Whole-Field Interferometric Scheme for Measuring strain and Flow Rates of Glacier and Other Natural Surfaces

Journal of Glaciology ◽

10.3189/s0022143000030392 ◽

1983 ◽

Vol 29 (103) ◽

pp. 492-497

Author(s):

Gary Cloud ◽

Edgar Conley

Keyword(s):

Displacement Vector ◽

Surface Displacement ◽

Time Lapse ◽

Speckle Interferometry ◽

Narrow Beam ◽

Coherent Light ◽

Ice Surface ◽

Glacier Ice ◽

Fringe Patterns ◽

Small Overlap

AbstractThe flow of glacier ice is mapped using high-resolution photography and non-coherent-light speckle interferometry. Young’s fringe patterns result when a double-exposed photoplate image of the straining surface is illuminated by a narrow beam of coherent light. Geometry gives a relationship between the ice surface displacement vector and the interference fringe patterns. This displacement vector is corrected for rigid-body (camera) movement and projected onto the ice surface using topological maps. The strain during the time-lapse interval is thus known. Comparison with data acquired by surveying techniques at Nisqually Glacier, Washington, U.S.A., is limited because of small overlap of the surface studied. In the areas for which results can be compared, our experiments yield a flow of 0.6 m/d where conventional methods yield about 0.4 m/d.

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