Optical Setup for Error Compensation in a Laser Triangulation System

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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Accuracy Analysis of Point Laser Triangulation Probes Using Simulation

Journal of Manufacturing Science and Engineering ◽

10.1115/1.2830214 ◽

1998 ◽

Vol 120 (4) ◽

pp. 736-745 ◽

Cited By ~ 26

Author(s):

K. B. Smith ◽

Y. F. Zheng

Keyword(s):

Contact Force ◽

Measurement Errors ◽

Specular Reflection ◽

Laser Triangulation ◽

Accuracy Analysis ◽

Soft Or ◽

Error Sources ◽

Internal Component ◽

Surface Reflectivity ◽

Component Models

Point Laser Triangulation (PLT) probes are relatively new noncontact probes being integrated with Coordinate Measuring Machines (CMMs). Two prominent advantages of PLT probes are fast measuring speeds (typically 100 to 1000 times faster than touch probes) and no contact force is required to take measurements making soft or fragile objects measurable. These advantages have motivated the integration of PLT probes onto CMM. However, because the PLT probe is an electro-optics device, many factors related to optics affect its operation, such as sensor-to-surface orientation and surface reflectivity. To study and better understand these error sources, PLT probe models are needed to simulate observed measurement errors. This article presents a new PLT probe model, which simulates observed measurement errors and shows the effects of placement and orientation of internal components. This PLT probe model is a combination of internal component models developed using geometrical optics. The model successfully simulates measurement errors from specular reflection observed experimentally with real PLT probes. The model also allows the parameters of internal components to be studied.

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On the use of optical fibres in a pulsed time-of-flight laser rangefinder

Robotica ◽

10.1017/s0263574700017471 ◽

1995 ◽

Vol 13 (1) ◽

pp. 45-53

Author(s):

Seppo Nissilä ◽

Juha Kostamovaara

Keyword(s):

Measurement Errors ◽

Measurement Accuracy ◽

Time Of Flight ◽

Optical Fibres ◽

Optical Pulses ◽

Bending Vibration ◽

Error Sources ◽

Measuring Devices ◽

Hot Surface ◽

Industrial Measurement

SummaryThe pulsed time-of-flight laser rangefinding technique has been used in many industrial measurement applications, including 3D-coordinate measuring devices, hot surface profilers and mobile robot sensors. Optical fibres, typically 1–10 m in length and 100–400 μm in diameter can be used to guide optical pulses to the separate sensing head of the measurement device. The use of a large multimode fibre may cause problems, however, when aiming at millimetre accuracy, as the construction and adjustment of the optics of the sensor head may affect the transit time linearity and measurement accuracy via multimode dispersion. Environmental effects, such as bending, vibration due to the moving sensing head and temperature, also cause measurement errors. The error sources are studied and characterized in this paper.

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Analasys of two low-cost and robust methods for indoor localisation of mobile robots

Facta universitatis - series Electronics and Energetics ◽

10.2298/fuee1703403p ◽

2017 ◽

Vol 30 (3) ◽

pp. 403-416 ◽

Cited By ~ 1

Author(s):

Milos Petkovic ◽

Vladimir Sibinovic ◽

Dragisa Popovic ◽

Vladimir Mitic ◽

Darko Todorovic ◽

...

Keyword(s):

Measurement Errors ◽

Low Cost ◽

Sampling Rate ◽

Cost Effective ◽

Robust Methods ◽

Lighting Conditions ◽

Measuring Devices ◽

Cost Distance ◽

Indoor Localisation ◽

Nelder Mead Algorithm

This paper presents two simple and cost effective indoor localisation methods. The first method uses ceiling-mounted wide-view angle webcam, computer vision and coloured circular markers, placed on the top of a robot. Main drawbacks of this method are lens distortion and sensitivity to lighting conditions. After solving these problems, a high localisation accuracy of ?1cm is achieved at about 5 Hz sampling rate. The second method is a version of trilateration, based on ultrasound time of flight distance measurement. An ultrasonic beacon is placed on a robot while wall detectors are strategically placed to avoid an excessive occlusion. The ZigBee network is used for inter-device synchronisation and for broadcasting measured data. Robot location is determined as a solution to the minimisation of measurement errors. Using Nelder-Mead algorithm and low-cost distance measuring devices, a solid sub 5 cm localisation accuracy is achieved at 10Hz.

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Substitutive Press-Bolster and Press-Ram Models for the Virtual Estimation of Stamping-Tool Cambering

Materials ◽

10.3390/ma15010279 ◽

2021 ◽

Vol 15 (1) ◽

pp. 279

Author(s):

Farshad Abbasi ◽

Alex Sarasua ◽

Javier Trinidad ◽

Nagore Otegi ◽

Eneko Saenz de Argandoña ◽

...

Keyword(s):

Cost Effective ◽

Medium Size ◽

Error Sources ◽

Static Loads ◽

New Approach ◽

Beam Elements ◽

Large Size ◽

The Press ◽

Final Adjustment ◽

Tooling System

Today’s stamping simulations are realized by ignoring the elastic deformation of the press and tooling system through the assumption of a rigid behavior and a perfect press stroke. However, in reality, the press and tool components deform elastically and are one of the major error sources for the final adjustment and blue-spotting of the dies. In order to tackle this issue, a new approach is proposed in this study that substitutes the press stiffness by means of a substitutive model composed of cost-effective shell and beam elements. The substitute model was calibrated using full-scale measurements, in which a 20,000 kN trial press was experimentally characterized by measuring its deformation under static loads. To examine the robustness of the substitute model, a medium-size tool and a large-size tool were simulated together with the substitutive model. To this end, a B-pillar tool was re-machined based on the substitute-model results and a new cambering procedure was proposed and validated throughout the blue-painting procedure. The newly developed substitute model was able to replicate the global stiffness of the press with a high accuracy and affordable calculation time. The implementation of the findings can aid toolmakers in eliminating most of the reworking and home-line trials.

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Utilization of the cyclic interferometer in polarization phase-shifting technique to determine the thickness of transparent thin-films

Optica Applicata ◽

10.37190/oa200106 ◽

2020 ◽

Vol 50 (1) ◽

Author(s):

Rapeepan Kaewon ◽

Chutchai Pawong ◽

Ratchapak Chitaree ◽

Tossaporn Lertvanithphol ◽

Apichai Bhatranand

Keyword(s):

Thin Films ◽

Beam Splitter ◽

Incident Light ◽

Reference Beam ◽

Phase Shifting ◽

Standard Equipment ◽

Polarized Beams ◽

Phase Shifting Technique ◽

Polarizing Beam Splitter ◽

Polarization Phase

An alternative polarization phase-shifting technique is proposed to determine the thickness of transparent thin-films. In this study, the cyclic interferometric configuration is chosen to maintain the stability of the operation against external vibrations. The incident light is simply split by a non-polarizing beam splitter cube to generate test and reference beams, which are subsequently polarized by a polarizing beam splitter. Both linearly polarized beams are orthogonal and counter-propagating within the interferometer. A wave plate is inserted into the common paths to introduce an intrinsic phase difference between the orthogonal polarized beams. A transparent thin-film sample, placed in one of the beam tracks, modifies the output signal in terms of the phase retardation in comparison with the reference beam. The proposed phase-shifting technique uses a moving mirror with a set of “fixed” polarizing elements, namely, a quarter-wave retarder and a polarizer, to facilitate phase extraction without rotating any polarizing devices. The measured thicknesses are compared with the measurements of the same films acquired using standard equipment such as the field-emission scanning electron microscope and spectroscopic ellipsometer. Experimental results with the corresponding measured values are in good agreement with commercial measurements. The system can be reliably utilized for non-destructive thickness measurements of transparent thin-films.

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A Lightweight and Cost-Effective 3D Omnidirectional Depth Sensor Based on Laser Triangulation

IEEE Access ◽

10.1109/access.2019.2914220 ◽

2019 ◽

Vol 7 ◽

pp. 58740-58750 ◽

Cited By ~ 3

Author(s):

Youngbin Son ◽

Seongwon Yoon ◽

Se-Young Oh ◽

Soohee Han

Keyword(s):

Cost Effective ◽

Laser Triangulation ◽

Depth Sensor

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Modeling of Absolute Distance Meter Shift Inside a Laser Tracker

Volume 3: Manufacturing Equipment and Systems ◽

10.1115/msec2017-3028 ◽

2017 ◽

Author(s):

He Li ◽

Robert G. Landers ◽

Douglas A. Bristow

Keyword(s):

Measurement Errors ◽

Radial Distance ◽

Radial Component ◽

Measurement Range ◽

Error Modeling ◽

Laser Tracker ◽

Absolute Distance ◽

Proposed Model ◽

Temperature Constant ◽

Shift Model

In the measurement of machine tool and robot geometric errors, one of the most extensively used instruments is the Laser Tracker (LT). Errors in the LT measurements will decrease the effectiveness of the error modeling and compensation methods that utilize these measurements. When the LT’s Absolute Distance Meter (ADM) is used without frequent referencing to a home position, large and long-term shifts occur. The ADM shift directly introduces errors in the radial component of every measurement in spherical coordinates, which will result in measurement errors in the Cartesian coordinates. Although the ADM shift is addressed in newer LT designs using internal referencing hardware, this paper presents a pragmatic and efficient software solution to ADM shift for LTs in which the internal referencing hardware is not embedded. The LT was measured for 22 hr in a temperature-constant room to examine the ADM shift effects on measurements. An ADM shift model was then proposed by assuming that the ADM shift equally affects radial components of all measurements wherever the target is, as long as it is within the measurement range. Another experiment was then performed to test the validity of the proposed model. After the model was identified and errors were corrected, the maximum temporal variation in the radial distance measurement is reduced by 80–86%.

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How Errors Cumulate: Two Examples

Journal of Survey Statistics and Methodology ◽

10.1093/jssam/smz019 ◽

2019 ◽

Vol 8 (3) ◽

pp. 413-432

Author(s):

Roger Tourangeau

Keyword(s):

Measurement Errors ◽

Total Error ◽

Internet Access ◽

Social Desirability Bias ◽

Item Nonresponse ◽

Error Sources ◽

Unit Nonresponse ◽

Different Types ◽

Nonresponse Error ◽

The Relationship

Abstract This article examines the relationship among different types of nonobservation errors (all of which affect estimates from nonprobability internet samples) and between nonresponse and measurement errors. Both are examples of how different error sources can interact. Estimates from nonprobability samples seem to have more total error than estimates from probability samples, even ones with very low response rates. This finding suggests that the combination of coverage, selection, and nonresponse errors has greater cumulative effects than nonresponse error alone. The probabilities of having internet access, joining an internet panel, and responding to a particular survey request are probably correlated and, as a result, may lead to greater covariances with survey variables than response propensities alone; the biases accentuate one another. With nonresponse and measurement error, the two sources seem more or less uncorrelated, with one exception—those most prone to social desirability bias (those in the undesirable categories) are also less likely to respond. In addition, the propensity for unit nonresponse seems to be related to item nonresponse.

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Straightener Settings for Under-Straight Residual Curvature of Reel Laid Pipeline

Volume 6B: Pipeline and Riser Technology ◽

10.1115/omae2014-24513 ◽

2014 ◽

Cited By ~ 1

Author(s):

Alan Roy ◽

Venu Rao ◽

Carlos Charnaux ◽

P. Ragupathy ◽

T. Sriskandarajah

Keyword(s):

Finite Element ◽

Thermal Expansion ◽

Residual Strain ◽

Axial Strain ◽

Cost Effective ◽

Pipe Material ◽

Finite Element Analyses ◽

Field Development ◽

Cost Effective Method ◽

Residual Curvature

The pipeline inplace buckling design by residual curvature method for controlled thermal expansion during operation is a novel and cost effective method for initiating multiple expansion loops for a reel-laid pipeline. The controlled thermal expansion will be initiated and managed by planned buckle sites at regular intervals of say, 1km spacing with residual curvature corresponding to 0.20%–0.25% residual strain. The pipelines installed by the reel Lay process are required to be straightened by a reverse curvature process which results in pipeline with nominally zero curvature and axial strain. In order to achieve a residual strain of 0.20%–0.25%, two options are available either to over-straight or under-straight the pipelines. This paper discusses the methodology used laying of pipeline with 0.20%–0.25% residual strain at pre-determined intervals by an under-straightening process with a combination of a central 40m under straight section with a residual strain of 0.2%–0.25% and a 15m transition section on either side of the central section, at 1km intervals. The paper presents the methodology used to determine the settings for the top straightener module of reel lay vessel using finite element analyses, as the equipment settings for under or over straight pipes are not readily available from analytical methods. The optimum settings were obtained after substantial number of FEA simulations allowing for the statistical range in pipe material properties from “strong” to “weak” and these settings are used in reeling trials to make necessary adjustments. The residual strain, out-of-straightness and axial force distributions in pipe sections for straight, under-straight and transition sections are discussed. The paper discusses how these settings were used on-board the vessel and the modifications and adjustments required to select the final settings for the under-straight curvature for the field development of Statoil Skuld project as a case study. This paper briefly discusses the vessel equipment specific features and limitations that may need to be taken into consideration in finite element analyses to optimise the straightener settings for residual strain.

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