• Title/Summary/Keyword: Ghost image

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Optical Design considering Efficiency Improvement of Aspheric Plastic Lens for LED Lighting (LED조명용 비구면 Plastic Lens의 성능향상을 위한 광학설계)

  • Lee, Hak-Suk;Park, Jong-Rak;Kim, Min-Jae;Kim, Hye-Jung;Kim, Jung-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.289-289
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    • 2009
  • Light emitting diode(LED) has many advantages including lower energy consumption and longer lifetime and eco-friendly in comparison with traditional light sources. Spheric plastic lens generally used in LED lighting occurs aberration and ghost image which give displeasure and deteriorate vision quality in human eyes. Using the optical program (LightTools$^{TM}$, CodeV$^{TM}$), we were confirm the aberration and ghost image in optical simulation and employed aspheric lens form in the lens design to improve these problems. From the comparison of the simulation results between the aspheric lens and the spheric lens, we were ascertain to be improved both aberration and Ghost image.

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Simple Denoising Method for Novel Speckle-shifting Ghost Imaging with Connected-region Labeling

  • Yuan, Sheng;Liu, Xuemei;Bing, Pibin
    • Current Optics and Photonics
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    • v.3 no.3
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    • pp.220-226
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    • 2019
  • A novel speckle-shifting ghost imaging (SSGI) technique is proposed in this paper. This method can effectively extract the edge of an unknown object without achieving its clear ghost image beforehand. However, owing to the imaging mechanism of SSGI, the imaging result generally contains serious noise. To solve the problem, we further propose a simple and effective method to remove noise from the speckle-shifting ghost image with a connected-region labeling (CRL) algorithm. In this method, two ghost images of an object are first generated according to SSGI. A threshold and the CRL are then used to remove noise from the imaging results in turn. This method can retrieve a high-quality image of an object with fewer measurements. Numerical simulations are carried out to verify the feasibility and effectiveness.

Evaluation of Unexposed Images after Erasure of Image Plate from CR System (CR 시스템에서 IP 잠상의 소거 후 Unexposed Image의 평가)

  • Lim, Bo-Yeon;Park, Hye-Suk;Kim, Ju-Hye;Park, Kwang-Hyun;Kim, Hee-Joung
    • Progress in Medical Physics
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    • v.20 no.4
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    • pp.199-207
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    • 2009
  • It is important to initialize Image Plate (IP) completely for removing residual latent image by sodium lamp for reliability and repeatability of computed radiography (CR) system. The purpose of this study was to evaluate latent images of computed radiography (CR) images respect to delay time after erasure of foregone latent image and its effect, and erasure level. Erasure thoroughness for CR acceptance test from American Association of Physicist in Medicine (AAPM) Report 93 (2006) was also evaluated. Measurements were made on a CR (Agfa CR 25; Agfa, BELGIUM) system. Chest postero-anterior (PA), Hand PA, L-spine lateral radiographs were chosen for evaluation. Chest phantom (3D-torso; CIRS, USA) was used for Chest PA and L-spine lateral radiography. For Hand PA radiography, projections was done without phantom. Except Hand PA radiographs, noise was increased with delay time, and ghost image was appeared on overexposed area. Effect of delay after erasure on latent image was not seen on naked eye, but standard deviation (SD) of pixel value on overexposed area was relatively higher than that of other areas. On Hand PA and Chest PA radiographs, noise were not occurred by adjustment of erasure level. On L-spine lateral images at lower erasure level than standard level, noise including ghost image were occurred because of high tube current. Erasure thoroughness of CR system in our department was to be proved by these evaluation. The results of this study could be used as a baseline for IP initialization and reliability of CR images.

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Fast Noise Reduction Approach in Multifocal Multiphoton Microscopy Based on Monte-Carlo Simulation

  • Kim, Dongmok;Shin, Younghoon;Kwon, Hyuk-Sang
    • Current Optics and Photonics
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    • v.5 no.4
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    • pp.421-430
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    • 2021
  • The multifocal multiphoton microscopy (MMM) enables high-speed imaging by the concurrent scanning and detection of multiple foci generated by lenslet array or diffractive optical element. The MMM system mainly suffers from crosstalk generated by scattered emission photons that form ghost images among adjacent channels. The ghost image which is a duplicate of the image acquired in sub-images significantly degrades overall image quality. To eliminate the ghost image, the photon reassignment method was established using maximum likelihood estimation. However, this post-processing method generally takes a longer time than image acquisition. In this regard, we propose a novel strategy for rapid noise reduction in the MMM system based upon Monte-Carlo (MC) simulation. Ballistic signal, scattering signal, and scattering noise of each channel are quantified in terms of photon distribution launched in tissue model based on MC simulation. From the analysis of photon distribution, we successfully eliminated the ghost images in the MMM sub-images. If the priori MC simulation under a certain optical condition is established at once, our simple, but robust post-processing technique will continuously provide the noise-reduced images, while significantly reducing the computational cost.

A Study for Renaming of Paekje's Designed Tiles -Centering Around the Ghost Image Design Excavated at Oe-ri Kyuam-myun, Buyeo- (백제 문양전의 개명(改名)을 위한 연구 -부여 규암면 외리 출토 '귀형문(鬼形文)'을 중심으로-)

  • Hong, Jae-Dong
    • Journal of architectural history
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    • v.10 no.3 s.27
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    • pp.7-23
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    • 2001
  • We Koreans are very proud of this nation's cultural history over some five millenniums. But most of the relics found in the nation date back up to two thousand years. Under this circumstance, we are wondering the gap and missing of three thousand years. In our traditional literature of history, [Chiwoo] was a military god of supreme dignity and virtue. He was a symbol of brave and strong warriors and since the antiquity, he has been kept alive deeply in the mind of the Korean race. Considering findings through this study, the researcher could provide a conclusion as described below. 1) The name of Paekje's designed tiles was initially made by a Japanese scholar who had first found the antique relic. According to studies by a few of Korean researchers, the name is usually called despite its relation with a historical background of the excavated objects has not been fully studied. 2) After the patterned objects of the Korean antique Kingdom, Japanese researchers reported that [Chiwoo] was a military god as exorcist and probably represented something in the form of a ghost, although there were arguments that the military god was the very being to influence the image of the ghost. This report suggests that the Japanese community didn't downgrade the military god onto the level of a ghost. 3) One of our antique nations, Paekje at that time sought to determine the origin and culture of the Koreans by making multiple exchange relations with China, and probably accepting cultures of the Chinese Han nation and those of the Chinese South and North Dynasty period. Based on findings from a relevant literature, [Sulyigi], people of Paekje attempted to show express the image of Chiwoo in their own unique ways and then deliver the strong bravery of [Chiwoo] to us, or their descendents. This can explain that those findings as above mentioned are consistent with the designed tiles of Paekje, and that the tiles should not be named as the design of ghost. 4) The designed tiles involved elements of Taoism and Buddhism and substantially considered the spirit of four gods which was mobilized for the tomb construction and selection at that time. But this should never be a reason why all of the horned figures seen in tomb wall paintings are collectively treated as ghosts. 5) From the view of historic literature, we can no doubt say that the Heavenly Emperor [Chiwoo] was our ancestor. It is not better to say that the relic stuffs as excavated should be referred to the design of ghost image only in that they have yet to be associated historically with other relics. This claim would be newly changed as it becomes clear with historical remains that our antique ancestors kept doing positive activities along the coast of the antique kingdom, Balhae.

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Development of OCB mode with impulsive driving scheme for improving moving picture quality

  • Kim, J.L.;Lee, C.H.;Park, S.Y.;Yoo, S.W.;Oh, J.H.;Lee, S.H.;Chai, C.C.;Park, C.W.;Ban, B.S.;Ahn, S.H.;Hong, M.P.;Chung, K.H.;Lim, S.K.;Kim, K.H.;Souk, J.H.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.1049-1052
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    • 2004
  • In general, contrary to the CRTs with impulsive emission, liquid crystal displays have motion artifacts such as blurring. ghost image, decrease of dynamic CR(contrast ratio), and stroboscopic motion due to hold type driving method. In this paper, to improve motion picture quality of LCDs. impulsive driving method of black data insertion was applied to the OCB mode which is well known for its fast LC response time and wide viewing angle properties. Subject evaluation was carried out with CRT, TN, SIPS(Super IPS). and impulsive driving OCB. Moving picture image quality near CRT was obtained in impulsive OCB driving mode

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Ghost Imaging With Classically Correlated Beams (고전 상관관계를 갖는 두 빛을 이용한 고스트 이미징)

  • Bae, Sam-Yong;Youn, Sun-Hyun
    • Korean Journal of Optics and Photonics
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    • v.16 no.6
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    • pp.481-484
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    • 2005
  • Quantum ghost imaging uses quantum mechanically entangled photons to form an image of an object. The quantum ghost image is also obtained by means of classical coincidence measurements with a classically correlated light source[1,2]. In this work we performed classical coincidence imaging experiments with classically correlated beams in their direction of propagation. We observed the ghost interference patterns which were usually made by quantum mechanically entangled states and we also analyze in detail the mechanism of the ghost imaging with classically correlated lights. We made? the classically correlated source with an Ar laser and controlled the direction of the light by a mirror? mounted on a small speaker.

A Study on Locational Control of Motion Ghost in Magnetic Imaging System (자기공명영상장치(磁氣共鳴映像裝置)에서 움직임허상(虛像)의 위치제어(位置制御)에 관(關)한 연구(硏究))

  • Lee, Who-Min
    • Journal of radiological science and technology
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    • v.16 no.2
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    • pp.19-26
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    • 1993
  • Magnetic Resonance Image represents three-dimensional diagnostic imaging technique using both nuclear magnetic resonance phenomenon and computer. Compared with computed tomography (CT), MRI have advantages harmless to patient's body, three-dimensional image with high resolution and disadvantages long data acquisition time because of long T1 relaxation time, relatively low signal to noise ratio, high cost of setting, also. As physiologic motion of tissue results in motion ghost in MRI, high 2.0Tesla make improve low signal to noise ratio. This study have aim to improve image quality with controling motion ghost of tissue. Supposing a moving pixel in constant frequency, one pixel make two ghosts which are same size and different anti-phase. So, this study will show adjust parameter on locational control of motion ghost. Author made moving phantom replaced by respiratory movement of human, researched change of motion frequency, FOV by location shift, and them decided optimal FOV (field of view). The results are as follows: 1. The frequency content of the motion determines how far the image always appear in phase-encoding direction, the morphology of the ghost image is characteristic of the direction of the motion and its amplitude. 2. Double FOV of fixed signal object for locational control of motion ghost is recommended. Decreasement of spatial resolution by increasing FOV can compensate on increasing of matrix in spite of scan time increasement.

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Terminal Guidance for Aerial Vehicles through Nadir-Looking Image Formation Using an Imaging Radar with a Rotating Antenna (회전하는 안테나를 가진 레이다를 이용하여 비행체 종말 유도를 위한 직하 방향 레이다 영상형성)

  • Lee, Hyukjung;Song, Sungchan;Chun, Joohwan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.4
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    • pp.328-331
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    • 2019
  • A linear frequency modulated pulse train waveform can be cost-effective in achieving high range resolution, and thus the synthetic aperture radar may be benefited by using the mixer output of the received signal. However, the image formation process from a mixer output is vulnerable to errors caused by stop-and-go approximation. In this paper, a nadir-looking imaging radar based on time domain correlation is proposed. Furthermore, to prevent the occurrence of ghosting effect in images, antenna placement on a rotating disk is proposed. Simulation results indicate that ghosting effect can be eliminated by employing the proposed antenna placement structure.

Range Design of Pulse Repetition Frequency for Removal of SAR Residual Image (영상레이더 잔상 제거를 위한 펄스 반복 주파수의 범위 설계)

  • Kim, Kyeong-Rok;Heo, Min-Wook;Kim, Tu-Hwan;Ryu, Sang-Burm;Lee, Sang-Gyu;Lee, Hyeon-Cheol;Kim, Jae-Hyun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.41 no.11
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    • pp.1653-1660
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    • 2016
  • The synthetic aperture rardar (SAR) is an active sensor using microwaves. It transmits a microwave signal, called a chirp pulse, and receives the reflected signal in a moving platform such as satellite and unmanned aerial vehicle. Since this sensor uses microwaves that can penetrate the atmosphere, SAR generates the images regardless of light and weather conditions. However SAR operates on the moving platform, the Doppler shift and the side-looking observation method should be considered. In addtion, a residual image or ghost image can be occurred according to selection of the pulse repetition frequency (PRF). In this paper, a range design of the PRF for the L-band spaceborne SAR system is studied for prevention of SAR image distortion. And the system is studied for prevention of SAR image distortion. And the system parameter and the PRF are calibrated iteratively according to the proposed system design procedure and design constraints. The MATLAB based on SAR system simulator has been developed to verify the validity of calculated PRF. The developed simulator assumes that SAR sensor is operated by the PRF calculated from the design. The results of the simulator show that the targets in image has a valid peak to side-lobe ratio (PSLR) so that the PRF can be used for the spaceborne SAR sensor.