• Journal of the Korean Society of Radiology
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• v.15 no.4
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• pp.525-531
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• 2021

The detector of the positron emission tomography (PET) is composed using a plurality of scintillation pixels and photo sensors. The use of multiple photo sensors increases cost and complicates signal processing. In this study, a detector with reduced cost and simple signal processing was designed using a small number of photo sensors. A scintillation pixel and a small number of photo sensors were used, and a optical guide was used to deliver light to all the photo sensors. A reflector is applied to the scintillation pixel and the optical guide to transmit the maximum amount of light to the photo sensor. A diffuse reflector and a specular reflector were used for the reflector, and a flood image was obtained by applying different thicknesses of the optical guide. An optimal combination was selected through comparative analysis of the acquired flood images. As a result, when specular reflectors were used for both the scintillation pixel and the optical guide, excellent flood images were obtained from optical guides of all thicknesses. For the optical guide, the optimal image was obtained when using a 3 mm thickness in consideration of the size of the image and the analysis of the point where the image of the scintillation pixel was formed.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.2 s.308
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• pp.19-29
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• 2006

As the security of personal information is becoming more important in mobile phones, we are starting to apply iris recognition technology to these devices. In conventional iris recognition, magnified iris images are required. For that, it has been necessary to use large magnified zoom & focus lens camera to capture images, but due to the requirement about low size and cost of mobile phones, the zoom & focus lens are difficult to be used. However, with rapid developments and multimedia convergence trends in mobile phones, more and more companies have built mega-pixel cameras into their mobile phones. These devices make it possible to capture a magnified iris image without zoom & focus lens. Although facial images are captured far away from the user using a mega-pixel camera, the captured iris region possesses sufficient pixel information for iris recognition. However, in this case, the eye region should be detected for accurate iris recognition in facial images. So, we propose a new fast iris detection method, which is appropriate for mobile phones based on corneal specular reflection. To detect specular reflection robustly, we propose the theoretical background of estimating the size and brightness of specular reflection based on eye, camera and illuminator models. In addition, we use the successive On/Off scheme of the illuminator to detect the optical/motion blurring and sunlight effect on input image. Experimental results show that total processing time(detecting iris region) is on average 65ms on a Samsung SCH-S2300 (with 150MHz ARM 9 CPU) mobile phone. The rate of correct iris detection is 99% (about indoor images) and 98.5% (about outdoor images).

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.154-160
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• 2006

전반사 성분은 직접 투사형 증강현실 시스템들이 가지는 대표적인 문제점으로서, 사용자의 시점에 따라 유동적으로 변하면서 프로젝션된 정보의 가시도(visibility)을 심각하게 저해한다. 이러한 전반사 성분의 발생을 해결하기 위해 여러 대의 중첩된(overlapping) 프로젝터를 이용하는 방법이 최근 제안되었다. 그러나, 전반사 성분은 사용자의 시점 뿐만 아니라, 스크린의 재질의 반사 특성에도 크게 좌우되는데, 이에 대한 고려가 없었다. 본 논문에서는 스크린의 재질에 따른 반사 특성을 고려함으로써, 보다 정확하게 전반사 성분을 검출, 회피하는 방법을 제안한다. 제안된 방법을 기존의 방법과 비교함으로써, 제안된 방법의 성능을 검증한다. 또한, 프로젝터 간의 기하 보정의 오차나 광학적 특성의 차이를 보완하기 위한 알고리즘을 개발, 이용함으로써 양질의 합성 결과를 제공해 준다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.267-270
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• 2000

강제가진을 받는 진동장은 직접장과 반사장으로 이루어진다. 직접장은 무한구조요소가 점입력을 받을 때의 해와 같으며, 반사장은 직접장에 의해 발생되는 1차 반사파 및 추가로 발생하는 무수한 반사파들의 합으로 나타낼 수 있다. 본 논문에서는 점가진을 받는 유한한 평판의 단일 주파수 해석을 수행하기 위한 레이추적기법을 연구하였다. 이를 위해, 직접장은 고주파수 가정을 이용하여 원형전달파로 근사화하고. 이 원헝전달파를 다수의 파동관 (wave tube)으로 이산화하였다. 균일한 경계조건과 무시할 만큼의 미약한 굴절효과를 가정하고 경계에서의 정반사 (specular reflection)만을 고려하여, 경계에서의 입사파동관. 전달 및 반사파동관의 기하학적 관계를 제안하였다. 이들 파동관이 평판 내부를 진행하면서 관측점에 미치는 영향들을 합성하여 비교적 정확한 강제진동응답을 얻을 수 있음을 단일 평판의 예제를 통하여 확인할 수 있었다 그러나, 연성된 평판의 경우에는 다소 부정확한 결과를 얻었다.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.64-75
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• 2010

This study introduces a complete feature map building method of sonar sensors for mobile robots. This method enhances the reality of feature maps by extracting even circle features as well as line and point features from sonar data. Edge features are, moreover, generated by combining line features close to circle features extracted around comer sites. The uncertainties of the specular reflection phenomenon and wide beam width of sonar data can be, therefore, reduced through this map building method. The experimental results demonstrate a practical validity of the proposed method in those environments.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.411-414
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• 2000

우리가 일반적으로 모니터에서 작업을 하는 경우 주로 백열등이나 형광등의 조명을 켠 상태에서 하게된다 이런 경우 모니터 상의 동일한 색도는 주위 조명이 바뀜에 따라 다르게 느껴지며 특히 주위 조명의 색도와 모니터의 색도가 틀린 경우는 더욱더 다르게 느껴진다[1]～[3]. 이 논문에서는 우리가 생활하는 일반 환경인 백열등이나 형광등 아래의 모니터 상에 영상을 재현 시 주위 조명의 영향을 고려한 색 재현 알고리즘을 제안한다. 임의의 환경에서 사람의 색 인식에 영향을 미치는 요소는 장면에 존재하는 조명의 색 특성과 물체의 색 특성에 의존한다. 단순한 물체의 표면 반사가 아닌 모니터 등의 조명 역할을 하는 표면이 존재하는 경우는 두 개 이상의 조명이 있는 형태이다. 두개 이상의 조명이 존재하는 경우, 사람들이 느끼는 백색점(white point)은 각 조명의 색도 벡터(chromaticity vector)의 조합으로 표현된다. 본 논문에서는 임의 환경에서 사람이 인식하는 백색점을 모델링하기 위하여 주위 환경이 백색점의 인식에 미치는 영향을 분석하였으며 모니터 상의 색 재현시 주위 조명의 영향을 주위 조명에 의해 생성되는 모니터 표면의 경면 반사(specular reflection)에 의한 영향과 인간 시각의 색 순응(color adaptation) 백색점의 변화 두 가지로 나누어 분석하였다.

• Proceedings of the Korea Multimedia Society Conference
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• 1998.04a
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• pp.385-388
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• 1998

The main interest of previous researches for shape from shading was only on Lambertian surface which consists of diffuse reflectance surface. In practice, natural objects have hybrid reflectance, which limits the recovery of shape from intensity distribution[1][2]. In this paper, we propose the method of determining shape using neural network and diffuse illumination. The segmented region of sphere surface is used for training set, which can be determined by shadow line and edge of surface. Diffuse illumination is used to avoid specular spike and highlight which usually cause many problems such as intensity disparities. Diffuse illumination method using flat paper allows us to reduce these phenomena with simple scheme. Neural network and Diffuse illumination method are useful for shape from shading, because it can be applied to objects of unknown reflectance properties, but it is applied only to Torrance-Sparrow style reflectance.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.579-581
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• 2006

Flat panel image display devices such as TFT LCD and PDP have required more large area and high quality control components. To control the qualities of the components, measurements of the flatness of a plate glass has been required. In order to measure the shape of the specular objects, Non-Contact Optical Sensor using Hologram laser unit was proposed. The sensor has a optical system that is composed of a Hologram laser and objective lens. The temperature of the sensor body is controlled by TEC(Thermoelectric Cooler) to maintain the same wavelength of the diode laser. In this research, we proposed the calibration scheme to make sensor real time measuring sensor. From the experimental results we see that the proposed sensor unit can measure the position of the glass surface in rial time.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.131-135
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• 1989

Hot electron simulation of silicon using Monte Carlo method was carried out to investigate impact ionization characteristics near the drain of MOSFET's at 77 and 300K. We successfully characterized drift velocity and impact ionization at 77 and 300K employing a simplified energy band structure and phonon scattering mechanisms. Woods' soft energy threshold model was introduced to the Monte Carlo simulation of impact ionization, and good agreement with reported experimental results was resulted by employing threshold energy of 1.7 eV. It is suggested that the choice of the critical angle between specular reflection and diffusive scattering of surface roughness scattering may be important in determining the impact ionization charateristics of Monte Carlo simulation near the drain of MOSFET's.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.600-602
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• 2005

Recently image display devices have become large and high quality. To control the qualities of the component, measurements of the shape and thickness of a plate glass has been required. In order to measure the shape of the specular objects, Non-Contact Optical Sensor using Hologram laser unit was proposed. The sensor has a optical system that is composed of a Hologram laser and objective lens used for CD Player, and the sensor showed high performance for measuring the shape and thickness of transparent plates. In the sensor, the temperature of the sensor body is controlled by TEC(Thermoelectric Cooler). In this paper, we proposed the measuring method to make better performance of sensor using focus error signal of a hologram laser unit. It can measure the shape and the thickness of transparent objects with the s-type focus error signal which is generated by the sensor while it goes to the object.