• Title/Summary/Keyword: Lambertian Source

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3D Shape Reconstruction of Non-Lambertian Surface (Non-Lambertian면의 형상복원)

  • 김태은;이말례
    • Journal of Korea Multimedia Society
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    • v.1 no.1
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    • pp.26-36
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    • 1998
  • It is very important study field in computer vision 'How we obtain 3D information from 2D image'. For this purpose, we must know position of camera, direction of light source, and surface reflectance property before we take the image, which are intrinsic information of the object in the scene. Among them, surface reflectance property presents very important clues. Most previous researches assume that objects have only Lambertian reflectance, but many real world objects have Non-Lambertian reflectance property. In this paper the new method for analyzing the properties of surface reflectance and reconstructing the shape of object through estimation of reflectance parameters is proposed. We have interest in Non-Lambertian reflectance surface that has specular reflection and diffuse reflection which can be explained by Torrance-Sparrow model. Photometric matching method proposed in this paper is robust method because it match reference image and object image considering the neighbor brightness distribution. Also in this thesis, the neural network based shaped reconstruction method is proposed, which can be performed in the absence of reflectance information. When brightness obtained by each light is inputted, neural network is trained by surface normal and can determine the surface shape of object.

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A Study on Lambertian Color Segmentation and Canny Edge Detection Algorithms for Automatic Display Detection in CamCom (저속 카메라 통신용 자동 디스플레이 검출을 위한 Lambertian 색상 분할 및 Canny Edge Detection 알고리즘 연구)

  • Han, Jungdo;Said, Ngumanov;Vadim, Li;Cha, Jaesang
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.11 no.5
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    • pp.615-622
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    • 2018
  • Recent advancements in camera communication (CamCom) technology using visible light exploited to use display as an luminance source to modulate the data for visible light data communication. The existing display-CamCom techniques uses the selected region of interest based camera capturing approach to detect and decode the 2D color coded data on display screen. This is not effective way to do communicate when the user on mobility. This paper propose the automatic display detection using Lambertian color segmentation combined with canny edge detection algorithms for CamCom in order to avoid manual region of interest selection to establish communication link between display and camera. The automatic display detection methods fails using conventional edge detection algorithms when content changes dynamically in displays. In order to solve this problem lambertian color segmentation combined with canny edge detection algorithms are proposed to detect display automatically. This research analysed different algorithms on display edge recognition and measured the performance on rendering dynamically changing content with color code on display. The display detection rate is achieved around 96% using this proposed solutions.

Design of an Ultrasmall Flexible-endoscope Illumination Optical System with Bat-wing Light Distribution

  • Ju-Yeop Yim;Chul-Woo Park;Mee-Suk Jung
    • Current Optics and Photonics
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    • v.7 no.6
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    • pp.755-760
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    • 2023
  • In this paper, an illumination optical system that can mitigate the saturation phenomenon in the center of an image (caused by the typical flexible-endoscope illumination system using LEDs with Lambertian light distribution) is designed. When an LED with Lambertian light distribution is used as a light source, the amount of light in the center of the endoscopic illumination system is relatively high, compared to the periphery, causing saturation in the image. Since this phenomenon causes difficulty in detecting the patient's lesion, it is necessary to find a lighting-system design that can alleviate the saturation phenomenon. Therefore, in this paper a lighting system with bat-wing light distribution, which can lower the intensity at the center and secure the maximum amount of light at the maximum light distribution angle, is designed. In addition, to check the performance of the designed lighting system, a simulation of illumination and luminance is conducted for a system using a common aspherical lens with otherwise the same components. As a result, it is confirmed that the lighting system designed in this paper effectively reduces the luminance value at the center and secures more luminance values at the periphery than the familiar lighting system.

Modeling and Analysis of Optical Property for High Power LED (고출력 LED 모델링 및 광학적 특성 분석)

  • Han, Jeong-A;Kim, Jong-Tae
    • Korean Journal of Optics and Photonics
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    • v.18 no.2
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    • pp.111-116
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    • 2007
  • A high power LED which is being used in many illumination applications as a new light source was simulated for its physical structure and then its optical properties were analyzed. To obtain accurate results from the designed LED model, properties of the die chip and reflector cup were varied. As a result, a high power LED model which has a radiation pattern of a Lambertian with its viewing angle of approximately $140^{\circ}$ and total included angle of $160^{\circ}$ was designed.

Design and Fabrication of Light Guiding Plate for Photobioreactor (광생물 반응기를 위한 도광판 설계 및 제작)

  • Park, Gi Chan;Kim, Hun;Shin, Seong Seon;Shin, Hyun Keel;Kim, Jongtye;Jeong, Sanghwa;Park, Jong Rak
    • Korean Journal of Optics and Photonics
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    • v.23 no.2
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    • pp.55-63
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    • 2012
  • We present results of optical design and fabrication of a light guiding plate (LGP) to be used as an illumination system for photobioreactors. Modeling of a light-emitting diode (LED) light source, a reflection film, and LGP patterns was performed. Especially, the LGP patterns were modeled as Lambertian scatterers. The modeling parameters (reflectance, scatterer width) were determined through matching simulations with the experimentally measured illuminance distribution for a test LGP. An LGP for an LED light source was designed with the extracted model parameters, and fabricated using a computerized numerical control machine. Optical characteristics including average illuminance and uniformity of illuminance distribution were measured for the fabricated LGP.

Optical Simulation Study on the Effect of Reflecting Properties of Reflection Films on the Performances of Collimating Films for the LCD Backlight Applications

  • Lee, Jeong-Ho;Ju, Young-Hyun;Park, Ji-Hee;Lee, Ji-Young;Nahm, Kie-Bong;Ko, Jae-Hyeon;Kim, Joong-Hyun
    • Journal of Information Display
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    • v.9 no.1
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    • pp.26-32
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    • 2008
  • The dependence of optical performances of collimating films such as prism films and pyramid films on the reflecting properties of reflection films were investigated by using a ray tracing technique. The angular distribution of the luminance and the on-axis luminance gain were obtained by using a simple backlight model composed of a reflection film, a virtual flat light source, and a collimating film. Three kinds of reflecting properties were used, which were a perfect Lambertian reflector, a perfect mirror reflector, and a reflector having both diffuse and specular properties. It was found that the on-axis luminance gain was the highest in the simulation where a mirror reflector was used, while the viewing angle was the widest where the Lambertian reflector was used. This result indicates that it is necessary to optimize the simulation condition such as the reflecting properties in order to predict the optical performances of collimating films accurately. Quantitative correlation between the optical characteristics of collimating films and the reflecting properties of reflection films can be used to improve simulation technique for the development and the optimization of collimating films for LCD backlight applications.

Self-developed Efficiency Measurement System of Organic Light-Emitting Diodes (자체 개발한 유기 발광 소자의 효율 측정 시스템)

  • Han, Wone-Keun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.07a
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    • pp.537-538
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    • 2005
  • A way of measuring an efficiency of organic light-emitting diodes are studied. The efficiency is obtained from the current-voltage-luminance characteristics of the devices. Basically, number of charge carriers are obtained from the current-voltage characteristics, and the number of photons are obtained from the current of Si-photodetector. The organic light-emitting diodes are assumed as a lambertian light source and a program is made for calculating the efficiency. A device structure of ITO/TPD/$Alq_3$/Al is manufactured using thermal-vapor evaporation. This device is set into a measuring system and measured the efficiency. The efficiencies are measured using the lab-made program and commercially available equipments. The obtained values are similar to each other within 10% uncertainty.

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Development of Surface-mount-type Crown-shaped Lens for Reducing Glare Effect of Light-emitting Diode Light Source (LED 광원의 눈부심 현상을 감소시키기 위한 표면 실장형 CR 렌즈 개발)

  • Park, Yong Min;Bang, Hyun Chul;Seo, Young Ho;Kim, Byeong Hee
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.23 no.1
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    • pp.64-68
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    • 2014
  • This paper introduces the use of a crown-shaped (CR) lens to effectively diffuse the light from a light-emitting diode (LED) without any loss in the light intensity, in contrast to polymer-bulb-type diffusers. The diffusion lens was designed based on the Snell's law, which describes the physical path of a ray passing through the boundary between different media. CR lenses were fabricated by polydimethylsiloxane (PDMS) casting and UV-embossing processes, which used a pre-designed metal mold and UV-curable resin, respectively. Through experiments and optical evaluations, it was verified that the newly proposed CR lens not only decreased the vertical light strength and glare effect from an LED light source but also improved the diffusion characteristics while maintaining the quality of the LED's light intensity.

Optical Design of an Omnidirectional Illumination System Using an Ultra Wide Converter (초광각 변환기를 이용한 전방위 조명 광학계의 설계)

  • Juho Lee;Jae Myung Ryu
    • Korean Journal of Optics and Photonics
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    • v.35 no.1
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    • pp.18-23
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    • 2024
  • In exhibition spaces such as art museums, lighting should primarily illuminate the walls where exhibits are displayed rather than the floor. Commonly used LED lighting consists of an LED and a diffusion plate that closely resembles a Lambertian light source with uniform light distribution at every angle. This type of illumination focuses on the floor surface where normal incidence occurs. Consequently, this general illumination method is not well-suited for effectively lighting the wall surface. Specifically, to illuminate a wall, it is necessary to increase the light intensity in areas with a large incident angle in the light distribution. In response to this issue, our study proposes an illumination system that uses an ultra wide converter to adjust the divergence angle from the light source to 180 degrees.

Development of Optical Pickup for ElectroAcoustic Guitar (일렉트로어쿠스틱 기타용 광 픽업의 개발)

  • Shin, Bong-Hi;Park, Young-Woo
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.5
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    • pp.417-422
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    • 2014
  • A guitar pickup is a transducer that converts string vibration to an electrical signal. The magnetic and piezo pickups are the most commonly used for the respective electric and electroacoustic guitars. The magnetic pickups are prone to magnetic interference between the steel strings and permanent magnets, while the piezo ones are not free from signal inference between the strings. Thus, this paper presents the development of an optical pickup for the electroacoustic guitar. The proposed optical pickup has the top-to-bottom structure. It uses two of Infrared (IR) Light Emitting Diode (LED) and one photodetector. The developed optical pickup is subjected to the evaluation with commonly used piezoelectric pickup. It becomes obvious that SNR with the optical pickup is increased by 45 percent in average, compared with the piezoelectric pickup. It can be concluded that the developed optical pickup has a potential to be applied to the acoustic guitar.