• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.04a
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• pp.176-194
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• 1991

A study on the Manufactiring of High-Precision Linear Scale by the Use of He-Ne Laser Interference Of late, along with the advancement of procision machining technology, the reauirement of super-precision measurement increases as time goes on, and the precision and accuracy of standard scale which is a basis of procision measurement has been cognized as a oriterion of industrial development in a nation. Up to now, mechanical and chemical methods have been widely employed to carve scale lines on linear scale, and it is impossible for the linear scale manufactured by means of those methods to guarantee the measurement with sub-micron level owing to errors attended with various problems. And the measuring length also bears errors subjected to the influence of surroundings condition, and shows inefficient circumstances in measurement on the ground of the complexity of measuring procedure as well as massive measuring apparatus. Hence in this paper, we described on technology by which we can carve scale lines thru optical method under the condition of laboratory by using rhcoherence of He-Ne two-mode stabilized laser and in turn, put it to practical use as linear scale for the measurment of lengrh. In this researchin the case of setting scale interval to 20 .mu. m, we employed super-precision scale-carving device associated by Ar larser and acoustic optical modulator in lieu of flsahing lamp scale-carving device, and we consequently obtained superior linear scales carved with precision and accuracy of .+-. 0.3 .mu. m.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.3
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• pp.86-92
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• 2001

Position controls are very important in semiconductor manufacturing devices, machine tools, precision measuring instruments, etc. to measure the distance of movement of moving objects in minute units and the accuracy of measurement for the moving distance in these devices affect the performance of the whole devices. Therefore, in those precision instruments, a sensing device that can measure the distance of movement with high-precision resolution is required. Thus an optical encoder that has such advantages as easy digital interface, economical price, and a resolution similar to that of laser interferometers can be used. In this paper, a interferometer-type linear scale with easy digital interface and high-resolution has been set up and measured the distance of movement based on the diffraction principle. Interference signals produced in this optical setup of the linear scale have beers digitalized through fabricated photodetectors and designed signal processing circuits. A resolution of 0.5${\mu}{\textrm}{m}$ is acquired from the experimental interferometer-type linear scale without for the movement of scales any additional dividing circuits. It is shown that from this experiment a high-resolution distance measurement device can be designed by a simple optical setup.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.170-174
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• 1999

The main scale of linear scale greatly affects on the precision of displacement measurement. Especially when needing the long range measurement, the length of main scale should be increased accordingly. In this paper, we propose a linear scale that uses laser interference pattern as main scale for long range measurement. The linear scale is similar to Michelson interferometer excepting that the reference mirror is tilted so as to obtain interference fringe pattern and a grating panel is attached on a quadratic photo diodes. Four kinds of grating having phase differences of 0, $\pi$ /4, $\pi$ /2, 3 $\pi$ /4 are arranged on the panel. The experimental results show that signals of - quadratic photo diode, A, B,$\overline{A}$ and $\overline{B}$ are cosine wavelike and successive signals have phase difference of $\pi$/4 each other. So the proposed method can achieve improved measurement resolution.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.130-135
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• 1999

The main scale of linear encoder greatly effects on the precision of displacement measurement. Especially when needing the long range measurement the length of main scale should be increased accordingly. In this paper we propose a linear encoder that uses laser interference pattern as main scale for long range measurement. The linear encoder is similar to Michelson interferometer excepting that the reference mirror is tilted so as to obtain interference fringe pattern and a grating panel is attached on a quadratic photo diodes. Four kinds of grating having phase difference of 0. $\pi$/4, $\pi$/2, 3$\pi$/4 are arranged on the panel. The experimental results show that signals of quadratic photo diode A, B, {{{{ {-}atop {A } }}}} and {{{{ {- } atop {B } }}}} are cosine wavelike and successive signals have phase difference of $\pi$/4 each other. So the proposed method can achieve improved measurement resolution.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.3
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• pp.82-92
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• 1991

A study on the manufacturing of High Precision Linear Scalr using He-Ne Laser interference Of late, along with the advancement of precision machining technology, the requirement of super precision measurement increases as time goes on, and the accuracy of standard scale which is a basis of precision measurement has been cognized as a criterion of industrial development in a nationl. In this paper, we described on technology by which we could carve scale lines thru optical method under the condition of laboratory by using the coherence of He-Ne two-mode stabilized laser and in turn, put it to practical use as linear scale for the measurement of length. Hence in this research in the case of setting scale interval to 20 ${\mu}m$, we employed super precision scale-carving device associated with Ar laser and acousto optic modulator in lieu of flashing lamp scale-carving device, and we obtained as experimental result superior linear scales carved within the accuracy of ${\pm}$0.3${\mu}m$.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.10
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• pp.147-154
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• 2000

A new hardware compensation method reducing displacement measurement errors, caused by tilt of index scale in moire linear encoders, has been developed. In conventional moire linear encoders, the detectors are aligned perpendicular to the line of moire fringes this structure is very sensitive to an unwanted tilt of the gratings. In this paper, a newly designed grating, called a phase-modulated grating, is developed to compensate for non-orthogonal errors. By using the phase-modulated grating instead of a conventional index, it is possible to reduce non-orthogonal errors of moire linear encoders.

• Radiation Oncology Journal
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• v.18 no.4
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• pp.345-354
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• 2000

Purpose : Conventional radiation therapy Portal images gives low contrast images. The purpose of this study was to enhance image contrast of a linacgram by developing a low-cost image processing method. Materials and Methods : Chest linacgram was obtained by irradiating humanoid Phantom and scanned using Diagnostic-Pro scanner for image processing. Several types of scan method were used in scanning. These include optical density scan, histogram equalized scan, linear histogram based scan, linear histogram independent scan, linear optical density scan, logarithmic scan, and power square root scan. The histogram distribution of the scanned images were plotted and the ranges of the gray scale were compared among various scan types. The scanned images were then transformed to the gray window by pallette fitting method and the contrast of the reprocessed portal images were evaluated for image improvement. Portal images of patients were also taken at various anatomic sites and the images were processed by Gray Scale Expansion (GSE) method. The patient images were analyzed to examine the feasibility of using the GSE technique in clinic. Results :The histogram distribution showed that minimum and maximum gray scale ranges of 3192 and 21940 were obtained when the image was scanned using logarithmic method and square root method, respectively. Out of 256 gray scale, only 7 to 30$\%$ of the steps were used. After expanding the gray scale to full range, contrast of the portal images were improved. Experiment peformed with patient image showed that improved identification of organs were achieved by GSE in portal images of knee joint, head and neck, lung, and pelvis. Conclusion :Phantom study demonstrated that the GSE technique improved image contrast of a linacgram. This indicates that the decrease in image quality resulting from the dual exposure, could be improved by expanding the gray scale. As a result, the improved technique will make it possible to compare the digitally reconstructed radiographs (DRR) and simulation image for evaluating the patient positioning error.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.12a
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• pp.145-148
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• 2000

Position-determining capacity is a very important condition in equipments for manufacturing semi-conductor or various instruments to measure physical displacement quantities of a moving object in submicron such as a distance of movement, direction, etc. and the accuracy of total system is influenced by detecting accuracy of these equipments. Therefore in this paper we have optically made up laser linear encoder based on optical diffraction principle to measure these displacement quantities and have processed optical signal using hardware-setup. In consequence we had acquired displacement for movement of scale using a diffraction grating by the accuracy of 0.5${\mu}{\textrm}{m}$ and had digitalized moving quantities of scale.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.16-16
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• 2002

Granular metal-insulator alloys, consisting of nano-scale magnetic particles in an insulating matrix are of unique consideration for the technological application and fundamental physics. They display a wide variety of unusual both linear and nonlinear electric-transport, optical and magnetooptical properties, especially for compositions close to the percolation threshold. (omitted)

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.5
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• pp.1-6
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• 2004

Measurements of circular motion accuracy of NC lathe have achieved with ball bar systems proposed by Bryan, but the ball bar systems have ifluenced on the measuring data by way of the accuracy of the balls and the contacts of balls and bar seats. Therefore in this study, error data during of circular motion of ATC(Automatic Tool Changer) of NC lathe will be acquired by reading zx plane coordinates using two optical linear scales. Two optical linear scales of measuring unit are fixed on z-x plane of NC lathe, and the moving part is fixed to ATC and then is made to receive data of coordinates of the ATC at constant time intervals using tick pulses comming out from computer. And then, error data files of radial direction of circular motion are calculated with the data read, and the aspect of circular motion are modeled to plots, and are analysed by means of statistical treatments of circularity, means, standard deviations etc.