• Journal of Biomedical Engineering Research
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• v.16 no.4
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• pp.525-532
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• 1995

In this paper, a new try to measure nonlinear propagation characteristics of the pulse along blood vessel by using bispectral analysis is introduced, and the possibility of its application to the medical diagnosis is shown. In this method, the waveforms of pulse motion of blood vessel at two separated measuring points on the wall were detected from Doppler frequency modulation of transmitted probing ultrasonic waves. Then the auto- and crossbispectrum of detected waveforms are calculated to estimate the quadratic NTF (nonlinear transfer function) between the two measuring positions. In order to show relationships between the NTF and the nonlinear propagation characteristics, computer simulations have been performed. As the propagation distance increases, harmonic frequency components in NTF increases broadly due to the nonlinear effect in the propagation of blood pulse. In order to represent this phenomena quantitatively, we propose a new parameter, dispersion ratio of WTF. Basic experimental system was constructed by using 3.5MHz probing ultrasonic waves and the preliminary experiments were carried out on ague phantom and human body. Experimental results showed the validity of the measurement system enoughly.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.28-32
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• 2009

In order to obtain high quality images of thin objects, we performed an experiment of proton radiography by using low energy protons generated from the interaction of an ultrashort ultraintense laser with solid targets. The protons were produced from a thin polyimide target irradiated by the laser pulse, and their maximum energy was estimated at up to 1.8 MeV. A CR-39 nuclear track detector was used as a proton radiography screen. The proton images were obtained by using an optical microscope and the spatial resolution was evaluated by a Modulation Transfer Function (MTF). We have achieved about $10\;{\mu}m$ spatial resolution of images. The obtained spatial resolution shows about $4{\sim}5$ times better value than the conventional X-ray radiography for inspection or non-destructive test (NDT) purpose.

• Korean Journal of Optics and Photonics
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• v.16 no.1
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• pp.50-55
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• 2005

A method for measuring the wavefront error and the modulation transfer function(MTF) of large aperture optics using an unequal path interferometer is presented. A bidirectional shearing interferometer is used for collimation testing of the measurement system. A large aperture Fizeau interferometer with long optical path difference measures the wavefront error of the optics under test by using a $\Phi$ 400 mm off-axis parabolic mirror. The MTF is also measured at the wavelength of the interferometer by changing the laser light into partially incoherent light. Test results of a $\Phi$ 300 mm Cassegrain type satellite telescope made in Korea are presented.

• Korean Journal of Optics and Photonics
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• v.16 no.1
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• pp.56-62
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• 2005

Because of the wide plane and the curved field of CRT rear projection high definition television, its MTF(modulation transfer function) can't be easily measured by the usual forward testing method. Then we propose a backward testing method for the MTF so that the object plane and the image analyzer of forward testing are located at positions opposite each other. We prefer to use the backward testing method because the forward testing method has poor accuracy caused by very small numerical aperture, low spatial resolutions, and long depth of focus. We found that the backward testing method was very easy to align and had high repeatability. We confirmed the confidence of results obtained by the backward testing method in comparison with designed results.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.149-158
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• 2006

We have analyzed various tolerances of the multi-configurative microscopic system for inspecting the wire-bonding of a reed frame by using the Gaussian bracket method and the equivalent lens method. The tolerances for the curvature and the thickness, which are axial symmetric tolerances, are given by varying the back focal length within a fecal depth under diffraction-limited conditions. Moreover, by using the trial and error method, the axial non-symmetric tolerances for decenter and tilt are established by assigning the 5% variation of MTF(modulation transfer function) at the spatial frequency of 50 lp/mm and at the field angle of 0.7 field. As the tolerances with the most probable distribution are distributed within the range of the decay rate of less than 5% independent of the probability distribution of tolerances, we can achieve completely the desired design performances of the multi-configurative microscopic system by using the various ranges of these tolerances.

• Journal of radiological science and technology
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• v.43 no.4
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• pp.251-257
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• 2020

This study was purpose to quantitative evaluation of edge method of modulation transfer function(MTF) and physical image characteristics of by obtain the optimal edge image by using magnetic resonance imaging(MRI). The MRI equipment was used (MAGNETOM Vida 3.0T MRI, Siemense healthcare system, Germany) and the head/neck matrix shim MR coil were 20 channels(elements) receive coil. The MTF results of showed the best value of 0.294 based on the T2 Nyquist frequency of 1.0 mm^-1. The MTF results of showed that the T1 image is 0.160, the T1 CE image is 0.250, T1 Conca2 image is 0.043, and the T1 CE (Concatenation) Conca2 image is 0.190. The T2 image highest quantitatively value for MTF. The physical image characteristics of this study were to that can be used efficiently of the MRI and to present the quantitative evaluation method and physical image characteristics of 3.0T MRI.

• Korean Journal of Optics and Photonics
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• v.32 no.4
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• pp.153-162
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• 2021

In this article, the design of a variable F-number and triple magnification infrared optical system is described. That is a two-in-one optical system that combines an infrared search and track (IRST) system and an electro-optical tracking system (EOTS), where an afocal optical system is added to the IRST optical system designed already. The performance target is determined by analyzing system performance, and then the specification in the optical system design is calculated. This optical system contains a warm stop making it possible that one optics has two different F/# by cutting the size of aperture, and that is designed to suit this optics. The system satisfies the requirement such as a modulation transfer function (MTF). For operational assessment, the movement of the focusing lens group is analyzed over the change of temperature and target distance. By using this optical system, it is possible to develop equipment having two functions, infrared searching and electro-optical tracking.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.314-321
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• 2019

The Self-Adaptive Vision Correction Algorithm (SAVCA) developed in this study was suggested for improving usability by modifying four parameters (Modulation Transfer Function Rate, Astigmatic Rate, Astigmatic Factor and Compression Factor) except for Division Rate 1 and Division Rate 2 among six parameters in Vision Correction Algorithm (VCA). For verification, SAVCA was applied to two-dimensional mathematical benchmark functions (Six hump camel back / Easton and fenton) and 30-dimensional mathematical benchmark functions (Schwefel / Hyper sphere). It showed superior performance to other algorithms (Harmony Search, Water Cycle Algorithm, VCA, Genetic Algorithms with Floating-point representation, Shuffled Complex Evolution algorithm and Modified Shuffled Complex Evolution). Finally, SAVCA showed the best results in the engineering problem (speed reducer design). SAVCA, which has not been subjected to complicated parameter adjustment procedures, will be applicable in various fields.

• Journal of radiological science and technology
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• v.42 no.5
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• pp.329-334
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• 2019

This study was purpose to quantitative evaluation of noise power spectrum(NPS) and studied the quantitative evaluation and characteristics of modulation transfer function(MTF) by obtain the optimal edge image by using Coil in magnetic resonance imaging(MRI) equipment through Fujita theory using edge method. The MRI equipment was used (Tim AVANTO 1.5T, Siemense healthcare system, Germany) and the head matrix coil were 12channels(elements) receive coil. The NPS results of showed the best value of 0.004 based on the T2 Nyquist frequency of $1.0mm^{-1}$, and the MTF results of showed that the T1 and T2 values were generally better than the T1 CE and T1 CE FC values. The characteristics of this study were to explain the characteristic method of image quality evaluation in general. To present the quantitative evaluation process and results in the evaluation of MRI image characteristics in radiology.

• Journal of radiological science and technology
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• v.45 no.1
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• pp.11-17
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• 2022

This study was purpose to quantitative assessment of the resolution characteristics by using American college of radiology(ACR) phantom for magnetic resonance imaging (MRI). The MRI equipment was used (Achiva 3.0T MRI, Philips system, Netherlands) and the head/neck matrix shim SENSE head coil were 32 channels(elements) receive MR coil. And the MRI equipment was used (Discovery MR 750, 3.0T MRI, GE medical system, America) and the head/neck matrix shim MC 3003G-32R 32-CH head coil were receive MR coil. As for the modulation transfer function(MTF) comparison result by using ACR magnetic resonance imaging phantom, the MTF value of the ACR standard T2 image in GE equipment is 0.199 when the frequency is 1.0 mm^-1 and the MTF value of the hospital T2 image in Philips equipment is 0.528. It was used efficiently by using a general sequence more than the standard sequence method using the ACR phantom. In addition it is significant that the quantitative quality assurance evaluation method for resolution characteristics was applied mutatis mutandis, and the result values of the physical image characteristics of the 3.0T MRI device were presented.