Limitation of a Line-of-Light Online Paper Surface Measurement System

Alam, Anzar; O’Nils, Mattias; Manuilskiy, Anatoliy; Thim, Jan; Westerlind, Christina

doi:10.1109/jsen.2014.2314753

Cited by 12 publications

(5 citation statements)

References 14 publications

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“…A calibration is however necessary in order to calculate heights in metric units. The mathematical relation between pixels and metric heights is described by (1) and (2). A staircase shaped object of known heights is designed to be used as calibration object.…”

Section: 5mentioning

confidence: 99%

“…There is vast amount of scientific publications describing various applications for laser scanning. Several of those applications for 3D scanning require precision and accuracy at micrometer scale [1][2][3]. In many industrial manufacturing processes the sharpness of edge in sawing, cutting, drilling, and milling tools is key to assure the quality of production.…”

Section: Introductionmentioning

confidence: 99%

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High Precision Laser Scanning of Metallic Surfaces

Amir

Thörnberg

2017

International Journal of Optics

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Speckle noise, dynamic range of light intensity, and spurious reflections are major challenges when laser scanners are used for 3D surface acquisition. In this work, a series of image processing operations, that is, Spatial Compound Imaging, High Dynamic Range Extension, Gray Level Transformation, and Most Similar Nearest Neighbor are proposed to overcome the challenges coming from the target surface. A prototype scanner for metallic surfaces is designed to explore combinations of these image processing operations. The main goal is to find the combination of operations that will lead to the highest possible robustness and measurement precision at the lowest possible computational load. Inspection of metallic tools where the surface of its edge must be measured at micrometer precision is our test case. Precision of heights measured without using the proposed image processing is firstly analyzed to be ±7.6 m at 68% confidence level. The best achieved height precision was ±4.2 m. This improvement comes at 24 times longer processing time and five times longer scanning time. Dynamic range extension of the image capture improves robustness since the numbers of saturated or underexposed pixels are substantially reduced. Using a high dynamic range (HDR) camera offers a compromise between processing time, robustness, and precision.

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Section: 5mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High Precision Laser Scanning of Metallic Surfaces

Amir

Thörnberg

2017

International Journal of Optics

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“…Li et al used the combined measurement method of multiple LDSs to construct an on-machine quality control system for an automobile engine cylinder [3]. Alarm et al designed and implemented an LDS-based on-machine measuring device for paper quality [4]. Brosed et al combined the LDS with a six-axis robot to realize the on-machine measurement for products with complex geometrical shapes [5].…”

Section: Introductionmentioning

confidence: 99%

A Laser-Based On-Machine Measuring System for Profile Accuracy of Double-Headed Screw Rotor

Dong

Sun

et al. 2019

Sensors

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Great length, large weight and other factors may cause difficulty in measuring the profile accuracy of the double-headed screw rotor. To solve this problem, an on-machine measuring system based on a laser-displacement sensor (LDS) was designed and implemented in this paper by taking an LXK100 four-axis whirlwind milling machine as the carrier. To improve the measurement accuracy of the system, the generalized variable-structural-element morphological method, polynomial interpolation algorithm and ellipse fitting method were first combined to realize the rapid subpixel centroid extraction from a noise-containing spot image, thus improving the data acquisition accuracy of the LDS, and then the hybrid method was experimentally verified. Next, a wavelet threshold function with high-order differentiability and adaptive wavelet coefficient contractility was constructed based on the hyperbolic tangent function, so as to inhibit the disturbance from random errors and preserve real profile information, and this method was simulated and verified. Subsequently, a smoothing algorithm for point cloud data was proposed based on the Lagrange multiplier method to avoid the defect of the piecewise curve-fitting method, that is, function continuity and differentiability could not be satisfied at piecewise points. Finally, the profile accuracy was calculated in real time according to the data reconstruction result and the machining quality was judged. The measurement experiment of the double-headed screw rotor indicates that the proposed on-machine measuring system can complete the profile accuracy measurement for a screw pitch within 39.7 s with measurement accuracy reaching ±8 μm, and the measurement uncertainties of the major axis, minor axis and screw pitch are 0.72 μm, 0.69 μm and 1.24 μm, respectively. Therefore, the measurement accuracy and efficiency are both remarkably improved.

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“…With respect to the impact of the measurement environment on the data acquisition accuracy of LT, Alam et al researched the impact of environmental factors such as temperature, humidity, mechanical vibration and external light on LT. Finally, Alam gave a calibration method to improve the data acquisition accuracy and used dual non-diffracting beams as a light source to enhance the anti-noise performance of laser measurement [ 15 ]. Herrmann and Otesteanu, in view of the phenomenon that LT acquires data unstably in the dark or in a strongly-reflective environment, proposed an algorithm for improving the line-detection stability of LT based on the geometric Brownian motion [ 16 ].…”

Section: Introductionmentioning

confidence: 99%

Measurement of Free-Form Curved Surfaces Using Laser Triangulation

Dong

Sun

Liu

et al. 2018

Sensors

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Laser triangulation (LT) is widely used in many fields due to its good stability, high resolution and fast speed. However, the accuracy in these applications suffers from severe constraints on the data acquisition accuracy of LT. To solve this problem, the optical triangulation principle, the object equation of the optical path relationship and the deviation of the laser spot centroid are applied to deduce a mathematical model. Therefore, the image sensor inclination errors can be quantitatively calculated, and the collected data are compensated in real time. Further, a threshold sub-pixel gray-gravity (GG) extraction algorithm is proposed; the gradient function and Gaussian fit algorithm are used to set thresholds to remove the impact of the spot edge noise area on the center location; and polynomial interpolation is employed to enhance the data density of the traditional GG method, thus improving the data acquisition accuracy of LT. Finally, the above methods are applied to on-machine measurement of the American Petroleum Institute (API) thread and the screw rotor, respectively. The experimental results prove that the proposed method can significantly improve the measurement accuracy of free-form curved surfaces using LT and that the improved laser spot center extraction algorithm is more suitable for free-form curved surfaces with smaller curvature and more uniform curvature changes.

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Limitation of a Line-of-Light Online Paper Surface Measurement System

Cited by 12 publications

References 14 publications

High Precision Laser Scanning of Metallic Surfaces

High Precision Laser Scanning of Metallic Surfaces

A Laser-Based On-Machine Measuring System for Profile Accuracy of Double-Headed Screw Rotor

Measurement of Free-Form Curved Surfaces Using Laser Triangulation

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