A Scheme for Enhancing Precision in 3-Dimensional Positioning for Non-Contact Measurement Systems Based on Laser Triangulation

Selami, Yassine; Tao, Wei; Gao, Qiang; Yang, Hongwei; Zhao, Hui

doi:10.3390/s18020504

Cited by 20 publications

(8 citation statements)

References 11 publications

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“…Past relevant research includes auto-focus technology in microscope systems [9]- [12], laser triangulation [13]- [16] and active auto-focus methods [4], [5], [8], [9]. The pinhole method [17], [18] and astigmatic defocus detection are the main active control auto-focus methods.…”

Section: Related Workmentioning

confidence: 99%

A Novel Auto-Focus Method for Image Processing Using Laser Triangulation

et al. 2019

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Limitations of the pinhole method and astigmatic defocus detection have difficulties in determining the direction of defocus and a restricted linear correction range. Here, a distance-measuring approach based on the laser triangulation principle is proposed with a corresponding mathematical model to overcome these problems and to satisfy the requirements of an industrial thin-film transistor liquid-crystal display (TFT-LCD) inspection microscope system in active auto-focus applications. The approach combines infrared light at a wavelength of 808 nm with visible light. The light reflected from the surface of the object reaches a CCD camera and forms a spot via a set of optical devices. To control a PZT to achieve real-time auto-focusing, a Gaussian curve fitting method is used to process the spot information with the presented mathematical model giving the relationship between the detection value and the defocus value focus error signal (FES). The preliminary experiments with a 50× objective lens show that the measured values are consistent with the theoretical values, have good linearity and possess a focusing accuracy of 0.2 µm within ±30 µm of the focal plane. The analysis of the experimental results proves the feasibility of using this method in industrial applications. Compared with the traditional method of microscope focus correction, this method has the advantages of high accuracy, good linearity, and fast focus speed for the actual requirements of industrial inspection processes. This method has been applied to the circuit board component defect detection in our laboratory. INDEX TERMS Optical images, laser triangulation, auto-focus, Gaussian curve fitting.

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Section: Related Workmentioning

confidence: 99%

A Novel Auto-Focus Method for Image Processing Using Laser Triangulation

et al. 2019

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“…The error introduced due to the laser spot center calculation can be decreased by improved image processing algorithms and by averaging over time or several laser spot positions. The latter can be done through the projection of several laser spot images onto the detector by using multiple lasers in a setup to increase the achievable sensor accuracy and avoid occlusions [36][37][38]. Moreover, a diffraction grating was used in front of the detector to generate multiple points [39,40].…”

Section: Introductionmentioning

confidence: 99%

Optical Setup for Error Compensation in a Laser Triangulation System

Kienle

Batarilo

Akgül

et al. 2020

Sensors

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Absolute distance measurement is a field of research with a large variety of applications. Laser triangulation is a well-tested and developed technique using geometric relations to calculate the absolute distance to an object. The advantages of laser triangulation include its simple and cost-effective setup with yet a high achievable accuracy and resolution in short distances. A main problem of the technology is that even small changes of the optomechanical setup, e.g., due to thermal expansion, lead to significant measurement errors. Therefore, in this work, we introduce an optical setup containing only a beam splitter and a mirror, which splits the laser into a measurement beam and a reference beam. The reference beam can then be used to compensate for different error sources, such as laser beam dithering or shifts of the measurement setup due to the thermal expansion of the components. The effectiveness of this setup is proven by extensive simulations and measurements. The compensation setup improves the deviation in static measurements by up to 75%, whereas the measurement uncertainty at a distance of 1 m can be reduced to 85 μm. Consequently, this compensation setup can improve the accuracy of classical laser triangulation devices and make them more robust against changes in environmental conditions.

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“…There have been approaches developed for the digitization of 3D objects in reverse engineering using laser triangulation scanning or laser point cloud data [10,11]. Quite a lot of previous works [12,13,14,15] have been carried out on laser-scanning-based multi-view 3D measurement and reconstruction, where key issues including calibration and reconstruction were addressed. Regarding calibration, Zhao [16] put forward a ball-plate-based calibration method and proposed using the particle swarm optimization (PSO) algorithm to solve the critical point-cloud sphere center-fitting problem in the calibration.…”

Section: Introductionmentioning

confidence: 99%

A Multi-View Stereo Measurement System Based on a Laser Scanner for Fine Workpieces

Song

Sun

Yang

et al. 2019

Sensors

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A new solution to the high-quality 3D reverse modeling problem of complex surfaces for fine workpieces is presented using a laser line-scanning sensor. Due to registration errors, measurement errors, deformations, etc., a fast and accurate method is important in machine vision measurement. This paper builds a convenient and economic multi-view stereo (MVS) measurement system based on a linear stage and a rotary stage to reconstruct the measured object surface completely and accurately. In the proposed technique, the linear stage is used to generate the trigger signal and synchronize the laser sensor scanning; the rotary stage is used to rotate the object and obtain multi-view point cloud data, and then the multi-view point cloud data are registered and integrated into a 3D model. The measurement results show a measurement accuracy of 0.075 mm for a 360° reconstruction in 34 s, and some evaluation experiments were carried out to demonstrate the validity and practicability of the proposed technique.

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A Scheme for Enhancing Precision in 3-Dimensional Positioning for Non-Contact Measurement Systems Based on Laser Triangulation

Cited by 20 publications

References 11 publications

A Novel Auto-Focus Method for Image Processing Using Laser Triangulation

A Novel Auto-Focus Method for Image Processing Using Laser Triangulation

Optical Setup for Error Compensation in a Laser Triangulation System

A Multi-View Stereo Measurement System Based on a Laser Scanner for Fine Workpieces

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