High resolution displacement detection by speckle pattern analysis : accuracy limits in linear displacement speckle metrology

Filter, Robert; Scharf, Toralf; Herzig, Hans Peter

doi:10.2971/jeos.2010.10035s

Cited by 5 publications

(6 citation statements)

References 11 publications

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“…The EZNCC algorithm is more straightforward to implement than fringe and phase-based analyses 3 ; besides, it surpasses the limits of traditional correlation computing, ensures high sensitivity, and avoids additional calibration points for large displacements. 10 Notwithstanding its merits, current algorithms with subpixel capabilities may outperform the EZNCC resolution. For instance, experimental results with 2D cross-correlation enabled ≤0.5 μm resolution over a 1000 μm range, 16 whereas theoretical analyses F I G U R E 2 Zero-mean normalized correlation (ZNCC) and extended zero-mean normalized cross-correlation (EZNCC) as a function of the displacement u.…”

Section: Displacementmentioning

confidence: 99%

“…9 Concerning displacement measurements, using additional calibration images allows for subtly extending the range; this approach becomes unfeasible as the measured distance increases. 10 Another attempt comprises choosing the laser wavelength or incidence angle to enhance the contrast of speckle granules, which demands intensive calibrations for every sample. 11,12 Deep learning algorithms have been applied to several speckle metrology setups as an alternative to improve the measurement resolution and dynamic range.…”

Section: Introductionmentioning

confidence: 99%

“…However, despite their improved sensitivity and resolution, most laser speckle systems are limited regarding the dynamic range, that is, the decorrelation between the test and reference images 9 . Concerning displacement measurements, using additional calibration images allows for subtly extending the range; this approach becomes unfeasible as the measured distance increases 10 . Another attempt comprises choosing the laser wavelength or incidence angle to enhance the contrast of speckle granules, which demands intensive calibrations for every sample 11,12 .…”

Section: Introductionmentioning

confidence: 99%

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Enhancing the measurement range of laser speckle systems

Cabral

Cordeiro

Fujiwara

2022

Micro & Optical Tech Letters

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Laser speckle-based systems provide sensitive measurements of displacement and stain. However, the typical saturation of correlation functions restricts the application of such techniques regarding their dynamic range. Therefore, this paper proposes using the extended zero-mean normalized cross-correlation (EZNCC) algorithm to automatically update the reference speckle image according to a programmable threshold, allowing for exceeding the decorrelation limit. Experiments investigated the effect of rigid body displacements and thermal strain at the light scattering surface (a ceramic container). The EZNCC yielded ~30 μm resolution over a continuous 1500 μm range for displacement measurements, and ~0.2°C resolution between 21.5°C and 61.5°C for the temperature analysis. As this method requires minor updates to the traditional correlation algorithms, the ENZCC does not require modifications to the optical setups, improving the dynamic range and ensuring the high sensitivity of speckle correlation systems in a feasible, straightforward approach.

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Section: Displacementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhancing the measurement range of laser speckle systems

Cabral

Cordeiro

Fujiwara

2022

Micro & Optical Tech Letters

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“…Although well understood, the techniques have only recently become viable for practical applications in manufacturing and robotics due to advances in camera and signal processing technology. This has led to renewed interest in the technique with researchers investigating new applications in robotics vehicle odometry [11,12] and robotic positioning and stabilisation applications [13,14].…”

Section: Introductionmentioning

confidence: 99%

A non-contact laser speckle sensor for the measurement of robotic tool speed

Charrett¹,

Bandari²,

Michel³

et al. 2018

Robotics and Computer-Integrated Manufacturing

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A non-contact speckle correlation sensor for the measurement of robotic tool speed is described that is capable of measuring the in-plane relative velocities between a robot end-effector and the workplace or other surface. The sensor performance has been assessed in the laboratory with sensor accuracies of ±0.01 mm/s over a ±70mm/s velocity range. The effect of misalignment of the sensor on the robot was assessed for variation in both working distance and angular alignment with sensor accuracy maintained to within 0.025 mm/s (<0.04%) over a working distance variation of ±5 mm from the sensor design distance and ±0.4 mm/s (0.6%) for a misalignment of 5 • . The sensor precision was found to be limited by the peak fitting accuracy used in the signal processing with peak errors of ±0.34 mm/s. Finally an example of the sensor's application to robotic manufacturing is presented where the sensor was applied to tool speed measurement for path planning in the wire and arc additive manufacturing process using a KUKA KR150 L110/2 industrial robot.

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“…Integrated micro-components can be monitored and controlled using reflectance measurements as presented by Piombini et al (Toward the reflectance measurement of micro components) [3]. Speckle formation during laser beam reflection can also be a very sophisticated tool for detecting ultra-precise displacements, as presented by Filter et al (High resolution displacement detection with speckles : accuracy limits in linear displacement speckle metrology) [4].…”

mentioning

confidence: 99%