• Proceedings of the IEEK Conference
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• 2000.06d
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• pp.114-117
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• 2000

In this paper, we proposed robust digital image watermarking based on modulation transfer function (MTF) of human visual system (HVS). Using the proposed method, robust watermarking is possible both in common image processing operations such as cropping and lossy compression and in geometrical transforms such as rotation, scaling, and translation, because it can embed watermark and template signal maximally using MTF of HVS. Experimental results show that the proposed watermarking method is more robust to several common image processing operations and geometrical transforms.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.6
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• pp.390-394
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• 2016

This paper presents a new comparison method for haze-removal algorithms in next-generation automotive systems. Compared to previous peak signal-to-noise ratio-based comparisons, which measure similarity, the proposed modulation transfer function-based method checks sharpness to select a more suitable haze-removal algorithm for lane detection. Among the practical filtering schemes used for a haze-removal algorithm, experimental results show that Gaussian filtering effectively preserves the sharpness of road images, enhancing lane detection accuracy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.629-634
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• 2000

This System is developed for the estimation of the Camera Lens Resolution. Signal data proportional to light intensity is obtained and sampled from the 2D CCD. Based on the measured signal. the MTF charateristcs of a camera lens are measured. We could measure the sagittal and tangential MTF in the on and off-axis at the same time. The automatic measurig methods for optimal image plane, magnification, and best marginal direction of test lens are presented.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.77-78
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• 2006

We introduced a new method for lens design that eyepiece is combined with the Navarro eye. Following Optimization of lens system-Navarro eye combination, final design has the modulation transfer function(MTF) of 0.9 at 50 cycle/mm.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.6
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• pp.937-943
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• 1990

In this paper, a subband coding scheme using the human visual system(HVS) model for encoding monochrome images is proposed to produce perceptually higher quality images compared with the regular subband coding scheme. The proposed approach first transforms the intensity image to the density image by a point nonlinear transformation. A frequency band dexomposition of the density image is carried out by means of 2-D seaprable quadrature mirror filters, which split the density image spectrum into 16 equall rate subbands. Bits are allocated among the subbands to minimize the weighted mean squar error (WMSE) for differential pulse code modulation(DPCM) coding of the subbands. The weight for each subband is calculated from the modulation transfer function (MTF) of the HVS model at corresponding frequencies. The performances of the proposed approach are evaluated for 256 * 256 monochrome images at the bit rates of 0.5, 0.75 and 1.0 bita per pixel. Computer simulation results indicate that using the HVS model yields more pleasing reconstructed images than regular subband coding approach which does not use HVS model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.10
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• pp.1821-1827
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• 2007

In this paper, an analytic transfer channel modeling function by impulse signal propagation effects in indoor power-line network are analysed. The modeled channel parameters of power line channel including background noise is applied to the OFDM system and we analysis BER for QPSK and 16-QAM modulation signals with simulation. By the representation of gain for OFDM modulation, we can estimate the characteristic parameters of OFDM in Broadband power line communication.

• Korean Journal of Optics and Photonics
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• v.25 no.1
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• pp.8-13
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• 2014

By using finite ray-tracing and curve fitting, a numerical method to determine the non-paraxial pupil function of a high-NA objective is presented. MTF degradations caused by the non-paraxial diffraction effect are analyzed for on-axial imaging of a far-infrared objective and aberration-free ellipsoidal mirror system. The ellipsoidal mirror system has the same paraxial specifications as the far-infrared objective.

• Progress in Medical Physics
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• v.3 no.2
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• pp.67-81
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• 1992

Lots of physical phenomena which deteriorate the faithfulness of radiological images exist. The most common types of degradation are a loss of resolution and an increase in noise. This article deals with resolution. factors that influence it. and its characterisation. The problem of resolution failure due to a generic blurring phenomenum is described diagramatically and mathematically. for both one dimensional and two dimensional signals. The definition of the point spread function. the line spread function. the convolution integral and the modulation transfer function are made. The concept of frequency domain operations using the Fourier Transform is also discussed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.5
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• pp.43-49
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• 2000

In this paper, a new control method is presented to reduce acoustic resonance phenomena of metal halide lamps with electronic ballasts. A behavior of frequency controlled resonant inverter is analyzed and the transfer function is obtained. An integrator as a current controller for ballast is employed. By using both a disturbance of the lamp power and spread spectrum effects for reducing acoustic resonance, an amplitude modulation is done by using the current controller with 200[Hz] sinusoidal wave. Arc stabilities of MH 250[W] lamps are studied with changing the modulation index. Experiments with two MH 250[W] lamps, made by different manufacturers, showed the validity of the proposed method.

• Progress in Medical Physics
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• v.19 no.4
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• pp.219-226
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• 2008

In this study, we have conducted characterization of imaging performance for a flat panel digital X-ray detector using amorphous Selenium and a-Si TFT which was developed by the authors. The procedures for characterization were in concordance with internationally recommended standards such as IEC (international electrotechnical commission). The measures used for imaging performance characterization include response characteristic, modulation transfer function (MTF), detective quantum efficiency (DQE), noise power spectrum (NPS), and quantum limited performance. The measured DQEs at lowest and highest spatial frequencies were 40% and 25% respectively, which was superior to that of commercial products by overseas vendor. The MTF values were significantly superior to that of CR and indirect type DRs. The quantum limited performance showed the detector was limited by quantum noise at the entrance exposure level below 0.023 mR, which is sufficiently low for general X-ray examination.