• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.114-118
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• 2001

HP Laser Interferometer Measurement System[HP5529A] is one of the most powerful equipment for measurement of the motion accuracy. The straightness measurement system of the HP5529A is composed of wollastone prism and reflector. In this system, straightness error is measured by relative lateral motion between prism and reflector. But rotating motion of prism or reflector as moving optic causes not real straightness error but additive straightness error. Especially unwanted straightness error as this becomes very large when reflector is used as moving optic and an interval between reflector and prism is distant. In this paper, the compensation method is proposed for removing additive error and experiment is carried out for theoretical verification.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.69-76
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• 2005

The laser interferometer system such as HP5529A is one of the most powerful equipment fur measurement of the straightness error in precision stages. The straightness measurement system, HP5529A is composed of a Wollaston prism and a reflector. In this system, the straightness error is defined as relative lateral motion change between the prism and the reflector and computed from optical path difference of two polarized laser beams between these optics. However, rotating motion of the prism or the reflector used as a moving optic causes unwanted straightness error. In this paper, a compensation method is proposed for removing the unwanted straightness error generated by rotating the moving optic and an experiment is carried out for theoretical verification. The result shows that the unwanted straightness error becomes very large when the reflector is used as the moving optic and the distance between the reflector and the prism is far. Therefore, the prism must be generally used as the moving optic instead of the reflector so as to reduce the measurement error. Nevertheless, the measurement error must be compensated because it's not a negligible error if a rotating angle of the prism is large. In case the reflector must be used as the moving optic, which is unavoidable when the squareness error is measured between two axes, this compensation method can be applied and produces a better result.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.400-407
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• 1995

The straightness property is one of fundamental geometric tolerances to be strictly controlled for guideways of machine tools and measuring machines. The staightness measurement for long guideways was usually difficult to perform, and it needed additional equipments or special treatment with limited application. In this paper, a new approach is proposed using the profile matching technique for the long guideways, which can be applicable to most of straghtness measurements. An edge of relativelly sthort length is located along a divided section of a long guideway, and the local straightness measurement is performed. The edge is then moved to the next section with several positions overlap. After thelocal straightness profile is measured for every section along the long guideway with overlap, the global straightness profile is constructed using the profile matching technique based on theleast squares method. The proposed techinique is numerically tested for two cases of known global straightness profile arc profile and irregular profile and those profiles with and without random error intervention, respectively. When norandom errors are involved, the constructed golval profile is identical to the original profile. When the random errors are involved, the effect of the number of overlap points are investigated, and it is also found that the difference between the difference between the constructed and original profiles is very close to the limit of random uncertainty with juist few overlap points. The developed technique has been practically applied to a vertical milling machine of moving table type, and showed good performance. Thus the accuracy and efficiency of the proposed method are demonstrated, and shows great potential for variety of application for most of straightness measuirement cases using straight edges, laser optics, and angular measurement equipments.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.3 s.192
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• pp.117-123
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• 2007

This paper describes a three-probe system that can be used to measure the parallelism and straightness of a pair of rails simultaneously. The parallelism is measured using a modified reversal method, while the straightness is measured using a sequential two-point method. The measurement algorithms were analyzed numerically using a pair of functionally defined rails to validate the three-probe system. Tests were also performed on a pair of straightedge rails with a length of 250 mm and a maximum straightness deviation of $0.05{\mu}m$, as certified by the supplier. The experimental results demonstrated that the parallelism-measurement algorithm had a cancellation effect on the probe stage motion error. They also confirmed that the proposed system could measure the slope of a pair of rails about $0.06{\mu}rad$. Therefore, by combining this technique with a sequential differential method to measure the straightness of the rails simultaneously, the surface profiles could be determined accurately and eliminate the stage error. The measured straightness deviation of each straight edge was less than $0.05{\mu}m$, consistent with the certified value.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.6
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• pp.607-614
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• 2013

In this study, effect of the sensor gain error is theoretically analyzed and simulated when mixed sequential two-prove method(MTPM) is applied for the precision measurement of straightness error of a linear motion table. According to the theoretical analysis, difference of the gain errors between two displacement sensors increases measurement error dramatically and alignment error of the straightedge is also amplified by the sensor gain difference. On the other hand, if the gain errors of the two sensors are identical, most of error terms are cancelled out and the alignment error doesn't give any influence on the measurement error. Also the measurement error of the straightness error is minimized compared with that of the straightedge's form error owing to close relationship between straightness error and angular motion error of the table in the error terms.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.1
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• pp.17-21
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• 2019

In this paper, a high precision straightness measurement system has been developed at low cost using a visible laser and CMOS image sensor. CMOS image sensor detected optical image and the variation of straightness was calculated by image processing. We have observed that the error of the developed straightness measurement system was 0.9% when a distance of 3m between laser and image sensor. And it can be applied to 3D printer and any other areas.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.26-31
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• 2008

A precision four-degree-of-freedom measurement system has been developed for simultaneous measurement of four motion errors of a linear stage, which include straightness and angular errors, The system employs a retro-reflector to detect the straightness errors and a plane mirror to detect the angular errors. A common-path compensation method for laser beam drift is put forward, and the experimental results show that the influences of beam drift on four motion errors can be reduced simultaneously. In comparison with the API 5D laser measuring system, the accuracy for straightness measurement is about ${\pm}1.5{\mu}m$ within the measuring range of ${\pm}650{\mu}m$, and the accuracy for pitch and yaw measurements is about ${\pm}1.5$ arc-seconds within the range of ${\pm}600$ arc-seconds.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.173-176
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• 2006

The purpose of this study is to investigate the cause of an error of prefounded column straightness and to measure the error during Top-Down construction. There are several causes of an error of prefounded column : (1) The columns are connected by welding or other methods. (2) concrete and aggregates are put in columns. (3) The columns are constructed during the construction. The error of column straightness is different for each column, and the tilting of columns is shown in one or two directions between floors. The additional loads caused by the error of straightness may give damage to buildings.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.203-206
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• 2001

This paper presents a straightness measurement system for flat and long workpieces. The measurement system consists of a laser optical unit, a CCD camera and processing system, and a carrier system with a stylus. The carrier system accompanies the stylus, which displaces a retroreflector along the surface profile. The optical unit is used to optically amplify the displacement of retroreflector. The CCD camera and processing system finally identifies the vertical displacement of the stylus unit. The developed system is applied to two surfaces: ground surface and LM guide surface. The experimental results show that the developed system can measure the straightness of flat surfaces within sub-micron error.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.107-113
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• 2002

This paper presents a straightness measurement system for flat and long workpieces. The measurement system consists of a laser, a CCD camera and processing system, a carrier system with a stylus, and some optical units. The carrier system accompanies the stylus, which displaces and retroreflector along the surface profile. The optical unit is used to optically amplify displacement of the stylus unit. The developed system is applied to a ground surface and a LM guide unit. The experimental results show that the developed system can measure the straightness of flat surface and moving systems.