• Journal of IKEEE
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• v.22 no.3
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• pp.605-612
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• 2018

In this paper, a new method for linear sweeping of wavelength swept laser has proposed, and the linear sweeping of 1kHz speed and 80nm range has realized by using this method. The proposed requires only one-shot calibration in the early stage on a wave pattern applied to FFP-TF. This makes the problem with nonlinear swept lasers like a cumbersome and time-consuming signal processing brought on by every recalibration to be resolved.

• Journal of Sensor Science and Technology
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• v.12 no.2
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• pp.79-87
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• 2003

In this paper, we propose a method to obtain a linear characteristic using soft computing for systems which have array sensors of nonlinear characteristics. Also a procedure utilizing the pattern information of array sensors without additional sensors is proposed to reduce disturbance effects. For a typical example, even a single CdS cell for CdS array has nonlinear characteristics. Overall linear characteristic for CdS array is obtained using fuzzy logic for each cell and overlapped portion. In addition, further improvement for linearization is obtained applying genetic algorithms for the parameters of membership functions. Also the effect of disturbing external light changes to the CdS array can be reduced without using any additional sensors for calibration. The proposed method based on fuzzy logic shows improvements for position measurements and disturbance reduction to external light changes due to the fuzziness of the shadow boundary as well as the inherent nonlinearity of the CdS array. This improvement is shown by applying the proposed method to the ball position measurements of a magnetic levitation system.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.9
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• pp.60-67
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• 2007

A signal conditioning circuit for capacitive displacement sensors was developed using a high frequency modulation/demodulation method, and its performance was evaluated. Since capacitive displacement sensors can achieve high resolution and linearity, they have been widely used as precision sensors within the range of several hundred micrometers. However, they inherently have a limitation in low frequency range and some nonlinearity characteristics and so a specially designed signal conditioning circuit is needed to handle these properties. The developed signal processing circuit consists of three parts: linearization, modulation/demodulation, and nonlinearity compensation. Each part was constructed discretely using several IC chips and passive elements. An evaluation system for precision displacement sensors was developed using a laser interferometer, a precision stage, and a PID position controller. The signal processing circuit was tested using the evaluation system in the respect of resolution, repeatability, linearity, and so on. From the experimental results, we know that a highly linear voltage output can be obtained successfully, which is proportional to displacement and the nonlinearity of output is less than 0.02% of full range. However, in the future, further investigation is required to reduce noise level and phase delay due to a low-pass filter. The evaluation system also can be applied effectively to calibration and evaluation of precision sensors and stages.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.372-379
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• 1998

A new 6 degrees-of-freedom micro stage, based on parallel mechanisms and actuated by using piezoelectric elements, has been developed for the application of micro positioning such as semiconductor manufacturing devices, high precision optical measurement systems, and high accurate machining. The micro stage structure consists of a base platform and an upper platform(stage). The base platform can effectively generates planar motion with yaw motion, while the stage can do vertical motion with roll and pitch motions with respect to the base platform. This separated structure has an advantage of less interference among actuators. The forward and inverse kinematics of the micro stage are discussed. Also, through linearization of kinematic equations about an operating point on the assumption that the configuration of the micro stage remains essentially constant throughout a workspace is performed. To maximize the workspace of the stage relative to fixed frame, an optimal design procedure of geometric parameter is shown. Hardware description and a prototype are presented. The prototype is about 150mm in height and its base platform is approximately 94mm in diameter. The workspace of the prototype is obtained by computer simulation. Kinematic calibration procedure of the micro stage and its results are presented.

• The Korean Journal of Applied Statistics
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• v.20 no.2
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• pp.281-290
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• 2007

Linear estimator, a weighted sum of the sample observation, is commonly adopted to estimate the finite population parameters such as population totals in survey sampling. The weight for a sampled unit is often constructed by multiplying the base weight, which is the inverse of the first-order inclusion probability, by an adjustment term that takes into account of the auxiliary information obtained throughout the population. The linear estimator using the weight adjustment is often more efficient than the one using only the bare weight, but its valiance estimation is more complicated. We discuss variance estimation for a general class of weight-adjusted estimator. By identifying that the weight-adjusted estimator can be viewed as a function of estimated nuisance parameters, where the nuisance parameters were used to incorporate the auxiliary information, we derive a linearization of the weight-adjusted estimator using a Taylor expansion. The method proposed here is quite general and can be applied to wide class of the weight-adjusted estimators. Some examples and results from a simulation study are presented.

• Journal of the Korean Graphic Arts Communication Society
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• v.23 no.1
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• pp.65-75
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• 2005

An accurate characterization of the display device is essential for better color matching. The calibration and characterization process in display device is needed to transform the device dependent color to the device independent color. The process of characterization performs a linearization and transforms the linearized values into the CIE XYZ tristimulus values. The purposes of this paper is to propose optimal color transformation method for accurate reproduction of original copy in display device and to explain the propriety of transformation method using specific variable for the power of gradation expression.