Dissertations / Theses on the topic 'Multiple light sources'

A crescente capacidade do poder computacional e a proliferação de dispositivos ao nosso redor vem permitindo o desenvolvimento de novas e sofisticadas interfaces para interação humano-computador que reagem à presença e ao estado de seus usuários. Como o olhar tem a capacidade de transmitir muitas informações sobre o usuário, rastreadores de olhar, dispositivos que estimam a direção para onde uma pessoa olha, tem papel importante no desenvolvimento de tais interfaces. Entre suas aplicações temos o auxílio a pessoas com dificuldades motoras, que podem utilizar um rastreador de olhar como substituto ao mouse, aplicações de diagnóstico, que estudam evidências do comportamento humano, ou ainda o desenvolvimento de interfaces que utilizem a informação sobre o olhar como um canal a mais de comunicação com o usuário para perceber suas intenções. Muitas técnicas para atingir tal objetivo foram desenvolvidas mas as tradicionais ainda oferecem certas dificuldades de uso para seus usuários como a intolerância a movimentos de cabeça e a necessidade de calibração por sessão de uso. Neste trabalho fizemos um levantamento de uma série de técnicas de rastreamento de olhar, indo das mais tradicionais até algumas mais recentes que visam melhorar a facilidade de uso destes sistemas. Uma das técnicas mais promissoras utiliza múltiplas fontes de luz fixadas nos cantos do monitor do computador. Através da análise da posição dos reflexos gerados por essas fontes de luz sobre a córnea, juntamente com a informação da posição da pupila, presentes em imagens capturadas do olho, é possível estimar o ponto observado no monitor. Devido às suas vantagens ela foi escolhida para estudo mais detalhado e implementação. Extensos testes utilizando simulações foram realizados para avaliar seu desempenho. Foi também desenvolvida uma extensão dessa técnica, utilizando um modelo mais preciso do olho, visando melhorar sua precisão. Ao final apresentamos nossa implementação, baseada nessa extensão da técnica original, que é tolerante a movimentação da face e mostramos os resultados obtidos em testes realizados com um grupo de usuários.<br>Recent advances in computing power and the proliferation of computing devices around us allowed the development of new computer interfaces which can react to the presence and state of its users. Since gaze can transmit a lot of information about the user, gaze trackers, devices that can estimate the direction which a person is looking at, have an important role in the development of such interfaces. Among gaze tracking applications, we have aid for people with limited motor skills, human behavior studies, and the development of interfaces that can take gaze information as an additional communication channel with the user. Lots of techniques have been developed to reach this goal, but they have some problems that make them hard to be widely used. These problems are the need of calibration for each use session and the need to keep the user\'s head still. In this work we studied some of the existing gaze tracking techniques, from the more traditional ones to more recent ones. One of the most interesting techniques makes use of multiple light sources fixed at the monitor\'s corners. By analyzing the positions of corneal reflections and the pupil present in captured images of the eye, it is possible to estimate the gaze point on the monitor screen. Due to its advantages this technique was chosen for a deeper study and implementation. Lots of experiments using simulated data have been carried out to validate the technique. Using a more accurate model of the eye, an extension for this technique was also developed to increase its precision. Finally, we present our implementation, that allows for large head movement, as well as test results obtained from real users.

碩士<br>國立交通大學<br>顯示科技研究所<br>102<br>Nowadays light-emitting diode (LED) is widely used for both indoor and outdoor illumination. Owing to the higher modulation bandwidth than the fluorescent lamp, LED is also promising light source for visible light communication (VLC). For achieving uniform illumination environment, delicate LED setup strategies are typically required for controlling the resulting indoor spatial field distribution. For the VLC application, different LEDs are driven by different data signals; hence each receiver may receive optical signals irradiated from different LEDs, and suffers from serious signal interference. To achieve high data rate VLC, it is crucial to solve the signal interference. Additionally, for indoor VLC application using multiple LEDs, it is possible to identify users’ location. Our researches focus on the applications of indoor VLC using multiple LED light sources. The thesis is mainly divided into three sections. In the first section, a model for our indoor VLC system is built. The interference induced signal performance degradation is analyzed by simulations and experiments. In the second section, multiple input multiple output (MIMO) technology is used in our indoor VLC system in order to increase the transmission capacity. Moreover, we evaluate the channel matrix of MIMO by calculating the condition number (CN), and propose improving the CN of channel matrix by rotating the receiver. Finally, we combine the MIMO system with the position identification scheme to achieve illumination, positioning and communication simultaneously. High positioning accuracy is achieved in experiment.

碩士<br>大葉大學<br>資訊管理學系碩士班<br>95<br>Economy has grown rapidly nowadays; therefore, protection of entrepreneurs and houses has been more and more essential. It makes perfect sense that a smart security monitoring system has become the focus of development and research in the field of information technology during the past few years. At present, most of the monitoring systems are handled by manpower, which is inefficient. It is highly likely that operators overlook some certain thing. As a result, it is highly needed to have an automatic video monitoring system. On the other hand, crime rate is far higher at nighttimes than daytimes. It is certainly a difficult but crucial to monitor at nights. In this study, inexpensive webcams are used as equipment of video capture. Also, they are utilized to detect and track mobile light sources the light source intruders bring in the dark. By doing so, we can estimate the track of the light source holder. In the process of tracking multiple light sources, this research takes many factors into account, including multiple-light interference, effect of reflection of background objects, holders or shades of furniture. However, it mainly focuses on tracking multiple-mobile lights in the dark and on estimation of the track of the holder. By harnessing 3225 images among 30 shots of all kinds of stimulations, we detect the location of light sources (the accurate rate is 94.36%) and judge the type of light source (the accurate rate is 93.39%), the distance and features of the light source the accurate rate 93.62%). The results and analysis of errors prove that methodology in this study works.

碩士<br>逢甲大學<br>通訊工程所<br>100<br>Most color constancy algorithms assume a single light source with uniform illumination across the scene. However, this assumption seldom holds in reality. The purpose of this thesis is to develop a color constancy scheme for multiple light sources. Firstly, the luminance of an input image is adjusted automatically and adaptively to eliminate strong variation of illuminating intensity. Then, a near white-balanced image is obtained by appropriately shifting the levels of red, green, and blue channels of the luminance adjusted image. A pixel-wise illumination chromaticity map is estimated from this near white-balance image. Finally, the illumination color of the multiple light sources is obtained by applying the k-means clustering algorithm to the illumination chromaticity map. A true white-balance could be achieved by considering the influence of each light source on every pixel. In addition, the illumination color estimation method developed by the proposed scheme could be applied to evaluate the white-balance performance of the state-of-the-art color image enhancement methods.

碩士<br>國立交通大學<br>資訊科學與工程研究所<br>101<br>Multiple light sources X-ray imaging can solve issues like instantaneous doses, low- luminance light source, Phase contrast imaging and so on. Nevertheless, the problem with the blurred images produced by multiple light source has to be overcome. We introduce a non-iterative restoration method to produce a satisfactory result using a reasonable amount of computing time.

碩士<br>國立中興大學<br>資訊科學與工程學系所<br>101<br>Generally, white balancing algorithm is based on a simplified hypothesis which supposes that the light in a scene comes from one single source and is evenly distributed in space. However, this theory is often against reality because there are different light sources existed in the real world. In this paper, we focus on a practical condition that white balancing for multiple light sources. Firstly, we divide an image into individual patches and assume that the light in each patch comes from one source and is evenly distributed in space. The hypothesis fits the settings of traditional white balancing algorithm for single light source, so it is applicable for each patch to calculate its light source. Secondly, the estimated light source in each patch will be grouped so we can get the major light source and the group average. To define accurately the major light source that affects the image, we combine patches in terms of their similarity to the group average and the estimated light source in each patch. Finally we use the white balancing algorithm for the image with multiple light sources. Both of the artificial and authentic images are used to verify the proposed method. Experimental results show that the effectiveness of the proposed method.

碩士<br>國立中央大學<br>光機電工程研究所<br>98<br>The main objective of this thesis is to discuss the optical system for the interior lighting with different light sources. By using the designed light guide element and other optical elements turn the point light source like LED or the linear light source like CCFL into uniformity surface light source. Also we can adjust the color or the color temperature of the lamp by using the red, green, blue or yellow LEDs. In order to establish the whole system model, we use optical simulation software. The system model includes light guide element, light source and reflector. In order to promote the efficiency of the lamp, we could use the reflection film or the reflection coating to turn the light which leak out from the light guide element back. Light which emitting from the light source transmit in the light guide element by total internal reflection. Until light touch the micro-structure which is created on the top of light guide element, it could change the moving direction and emit from the light guide element. The first step is designing the size and the density of the micro-structure which is created on the light guide element to control the uniformity. We first use the CCFLs to design the whole model, and then add LEDs into the model. Finally the uniformity of the system could reach 85%. And we could adjust the color rendering property of the system by changing the position of LEDs or the different types of LED. After the adjustment, the average color rendering index of the system could reach 93. Adjusting color and color temperature of the whole system by changing the ratio of each light source and the range of color temperature could be adjusted form 6500K to 2700K, and then we could discuss the color uniformity and the color rendering property of the system. Finally, we design a lighting lamp with multiple light sources. We could use single light source as lighting. Also we could use both two light sources to change the color temperature of the lamp or adjust the color rendering property of the lamp. According to using different light sources with different colors or different arrangement of light sources, the color temperature which could be adjusted and the color rendering property would be different.

Multiple light source optical flow is a method to compute a dense, local representation of optical flow. The basic idea is to overcome the aperture problem using multiple images of a moving object acquired simultaneously under different conditions of illumination. Each image provides one linear constraint equation. When the optical flow and the 2D motion field coincide these equations are in the same unknowns. Two equations are enough to calculate both velocity componentss. Three or more images over-determine the system, allowing the calculation of confidence measures and making the computation more robust. This thesis presents a parallel, near-real-time implementation of multiple light source optical flow. Three light sources, one red, one green, and one blue, with negligible overlap in the visible spectrum illuminate the work place from different directions. Three separate black and white images corresponding to the three light sources are acquired simultaneously through a 3 CCD 24 bit RGB camera. The processing is done using a network of six independent processors. The encoded optical flow is displayed on a video monitor. For an image of size 240x240 pixels the processing rate is 4 frames/sec. The range of linear behaviour of the system was studied. A comparison with other methods on a synthetic and a real image sequence is presented.

碩士<br>國立成功大學<br>機械工程學系碩博士班<br>101<br>The research of developing the microassembly system is realized by utilizing the industrial computer with LabVIEW software for the control and man-machine interface. This thesis improves the illumination and imaging function by allocating multiple light sources in different directions so that the edge features of object in microassembly process can be clearly imaged. In addition, enhance features of the object edges can be obtained by switching of different illumination direction of light source. By utilizing the relationship between the object and its shadow in an image to locate the object position, precise positioning of the object is obtained to achieve automated assembly operation. This research uses software to simulate the CCD images for the changes of scattering light field and evaluate different light source configurations related to the image of assembling peg and hole. In the automation of micropeg and hole assembly test, consecutive assembly of two micro pegs of 80μm diameter with holes of 100μm diameter, with clearance ratio 0.2, are undertaken and analyzed.

碩士<br>大葉大學<br>資訊管理學系碩士班<br>97<br>Generally, the living environment is dimmer at night; therefore, it is possible for thieves invade our house at this time and increase the crime rate. Accordingly, light is necessary in the living environment but moving object will cause a wrong judgment when wisdom supervisory system detect the moving object. The main reason is moving object will be affected by multi-light environment and project several shadow. For this purpose, this research is about eliminating objective shadows in order to make wisdom supervisory system can precisely detect the moving object. The light sources mainly come from the white and yellow lights which we usually see in general living environment. Before the research, the procedure is to adjust different color of light, create different shadow modes of impenetrable object, and automatically judge the characteristics of environmental light by shadow projection of corrector.

The classic optical flow constraint equation is accurate under conditions of translation and distant light sources, but becomes inaccurate under conditions where the object may rotate or deform. The inaccuracies are generally a result of the changing intensities at points under rotation or deformation. The changing intensities of these points are associated with the changing surface gradients. We investigate a novel approach to multiple light source optical flow under known reflectance properties. This novel approach is specialized for translation and for rotation around axes which are parallel to the optical axis. The assumption that the object is moving under translation, rotation, or a combination of translation androtation in the image plane allows us to introduce a physical surface area constraint. Even with this additional constraint, however, the problem still remains locally underdetermined. At each time frame, our multiple light source optical flow approach assumes that three images are acquired from the same viewpoint, but under three different illumination conditions. Photometric stereo determines many of the coefficients in our underdetermined system, which has six equations in seven unknowns at each pixel in the image. Two of the unknowns are the optical flow components. Another three of the unknowns are the total derivatives of the three intensities with respect to time. The last two are the total derivatives of the surface gradients with respect to time. A variety of local regularization methods were investigated to select optical flow estimates which best matched the known motion fields. All the experimental results for this approach were obtained from synthetic data, in which the motion fields were known.

碩士<br>國立臺灣師範大學<br>光電科技研究所<br>92<br>In this thesis, we design a multi-channel multi-wavelength fiber ring spectrum sliced light source with a 8×8 array waveguide grating, semiconductor optical amplifier and 2×2 optical fiber coupler. The light source structure would be integrated into the novel 32×32 fiber optical wavelength switching network. In this spectrum sliced structure, we used the current source to excite the electron-hole pair that produce the broadband amplified spontaneous emission (ASE) light source. And then, we used the characteristic that multichannel and wavelength-division of 8×8 array waveguide grating to complete the multi-channel multi-wavelength fiber ring spectrum sliced light source to construct the transmitted test source for wavelength division multiplexed switching network systems. In the 32×32 optical wavelength routing switching network, we put the 2×2 optical wavelength switch into various traditional optical switching networks. First, we study the characteristic of blocking for the various traditional optical switching networks based on 2×2 optical wavelength switch and then choose the Dilated Benes and Modified Dilated Benes optical switching networks. We demonstrate the signal-to-noise ratio formulate for the 4×4, 8×8, 16×16 and 32×32 optical wavelength switching network based on 2×2 optical wavelength switch . Final, we integrated the multi-channel multi-wavelength fiber ring spectrum sliced light source and 32×32 optical wavelength routing switching network to analyze the performance for various data rate.