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Robust and accurate visual echo cancellation in a full-duplex projector-camera system

IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 2008年第10期30卷 1831-1840页

作者： Liao, Miao Yang, Ruigang Zhang, Zhengyou Univ Kentucky Dept Comp Sci Lexington KY 40507 USA Microsoft Corp Microsoft Res Redmond WA 98052 USA

In this paper, we study the problem of "visual echo" in a full-duplex projector-camera system for telecollaboration applications. Visual echo is defined as the appearance of projected contents observed by the camera. It can potentially saturate the projected contents, similar to audio echo in telephone conversation. Our approach to visual echo cancellation includes an offline calibration procedure that records the geometric and photometric transfer between the projector and the camera in a lookup table. During runtime, projected contents in the captured video are identified using the calibration information and suppressed, therefore achieving the goal of canceling visual echo. Our approach can accurately handle full-color images under the arbitrary reflectance of display surfaces and the photometric response of the projector or camera. It is robust to geometric registration errors and quantization effects and is therefore particularly effective for high-frequency contents such as texts and hand drawings. We demonstrate the effectiveness of our approach with a variety of real images in a full-duplex projector-camera system.

关键词： visual echo cancellation projector-camera system geometric calibration photometric calibration whiteboard-camera system teleconferencing collaboration

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Bare-fingers Touch Detection by the Button's Distortion in a projector-camera system

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IEEE TRANSACTIONS ON CIRCUITS AND systemS FOR VIDEO TECHNOLOGY 2014年第4期24卷 566-575页

作者： Hu, Jun Li, Guolin Xie, Xiang Lv, Zhong Wang, Zhihua Tsinghua Univ Dept Elect Engn Beijing 100084 Peoples R China Tsinghua Univ Inst Microelect Beijing 100084 Peoples R China

In this paper, we propose a novel interactive projection system (IPS), which enables bare-finger touch interaction on regular planar surfaces (e.g., walls, tables), with only one standard camera and one projector. The challenge of bare-finger touch detection is recovering the touching information just from the 2-D image captured by the camera. In our method, the graphical user interface (GUI) button is projected on the surface and is distorted by the finger when clicking it, and there is a significant positive correlation between the button's distortion and the finger's height to the surface. Therefore, we propose a novel, fast, and robust algorithm, which takes advantage of the button's distortion to detect the touch action. The proposed touch detection algorithm is performed in three stages: 1) region of interest extraction through a homography mapping, by which the computational complexity of the following processing is reduced;2) the button's distortion detection using a special edge detection algorithm, which greatly reduces the errors due to the influence of the finger's shadows and edges;and 3) touch action judgment by the button's distortion. Several applications (e. g., virtual keyboard, power point viewing), which use the proposed touch detection method based on the buttons, are shown in this paper. An evaluation is performed on the virtual keyboard and the results demonstrate that the proposed approach can detect bare-finger touch in real time with the missed detection rate of 1.00%, false detection rate of 2.08%, and touch detection rate of 96.92% at the typical projected distance.

关键词： Edge detection human-computer interaction projector-camera system touch detection triangulation

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Pro-Cam SSfM: projector-camera system for structure and spectral reflectance from motion

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VISUAL COMPUTER 2023年第4期39卷 1651-1666页

作者： Li, Chunyu Monno, Yusuke Okutomi, Masatoshi Tokyo Inst Technol Sch Engn Dept Syst & Control Engn Tokyo Japan

Image-based reconstruction of an object's 3D shape having the wavelength-by-wavelength spectral reflectance property enables higher-fidelity object 3D modeling compared with typical RGB-based modeling. In this paper, we propose a novel projector-camera system for practical and low-cost acquisition of a dense object 3D model with the spectral reflectance property. Different from existing spectral 3D data acquisition systems that use a dedicated multispectral camera or light, we use a standard RGB camera and an off-the-shelf projector as active illumination for both the 3D reconstruction and the spectral reflectance estimation. We first propose a calibration-free multi-view structured-light method to reconstruct the 3D points while estimating the intrinsic parameters and the poses of both the camera and the projector, which are alternately moved around the object during our image acquisition procedure. We then exploit the projector for multispectral imaging and estimate the spectral reflectance of each 3D point based on a novel spectral reflectance estimation method considering the geometric relationship between the reconstructed 3D points and the estimated projector positions. Experimental results on both synthetic and real data demonstrate that our system can precisely acquire a dense spectral 3D model using off-the-shelf devices.

关键词： projector-camera system Structured light Structure from motion Spectral reflectance estimation

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Color refinement using deep neural networks for enhancing color recognition in a projector-camera system

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JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY 2019年第12期27卷 795-805页

作者： Kang, Changgu Kim, Meekyoung Lee, Sung-Hee Gyeongnam Natl Univ Sci & Technol Jinju South Korea Daegu Univ Gyongsan South Korea Korea Adv Inst Sci & Technol Daejeon South Korea

In projector-camera systems, object recognition is essential to enable users to interact with physical objects. Among several input features used by the object classifier, color information is widely used as it is easily obtainable. However, the color of an object seen by the camera changes due to the projected light from the projector, which degrades the recognition performance. To solve this problem, we propose a method to restore the original color of an object from the observed color through camera. The color refinement method has been developed based on the deep neural network. The inputs to the neural network are the color of the projector light as well as the observed color of the object in multiple color spaces, including RGB, HSV, HIS, and HSL. The neural network is trained in a supervised manner. Through a number of experiments, we show that our refinement method reduces the difference from the original color and improves the object recognition rate implemented with a number of classification methods.

关键词： color refinement deep neural networks projector-camera system

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Clipping Error Rate-Adaptive Color Compensation Based on Gamut Extension for a Low-Performance camera in a projector-camera system

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IEEE TRANSACTIONS ON CONSUMER ELECTRONICS 2011年第3期57卷 1010-1017页

作者： Kim, Kyoungjae Cho, Jinsoo Samsung Elect Co Ltd Suwon Gyeonggi Do South Korea Kyungwon Univ Coll Informat Technol Dept Comp Engn Songnam 461701 Gyeonggi Do South Korea

As projectors become smaller and less expensive, the use of mobile (or portable) projectors is significantly increasing in environments where an ideal white screen is not readily available. Images from mobile projectors in this environment are often reproduced with visually distracting color distortion due to the use of arbitrary colored projection surfaces. In this paper, we propose an adaptive color compensation method that compensates for color distortion occurring in images projected onto an arbitrary colored projection surface without requiring use of a high-performance camera in a projector-camera system. The proposed method is based on gamut extension of a low-performance camera for device characterization and uses an adaptive clipping error reduction algorithm. Experimental results show that the proposed method effectively compensates for color distortion with an affordable low-performance camera, making the projector-camera system far more practical and marketable.

关键词： Color compensation projector-camera system gamut extension clipping error reduction

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Development of an Information Projection Interface Using a projector-camera system

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ELECTRONICS AND COMMUNICATIONS IN JAPAN 2013年第11期96卷 70-81页

作者： Goto, Hiroki Takemura, Daisuke Kawasaki, Yuzo Nakamura, Akio Tokyo Denki Univ Tokyo Japan Tokyo Denki Univ Dept Mech & Informat Engn Tokyo Japan

This paper proposes an interface system that enables a user to input and obtain information independent of position within a certain area in an environment with a projector-camera system. Hand gestures detected in the image are used as a cue to start the system, to distinguish gestures based on the user's intention to operate the system from other daily-life motions, and to specify the position of the user's hand. Hand gesture detection is implemented based on a combination of the background subtraction method and skin color extraction. The user can designate the projection area freely on a flat surface in the environment with his/her hand. The projector is mounted on a pan-tilt unit that projects information according to the user's indications. Then, the user's fingertip is detected using simple template matching and he/she interacts with the projected information to input commands without any equipment. As one application, we developed an interface system to operate electrical appliances such as a television intuitively in an everyday environment. (c) 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(11): 70-81, 2013;Published online in Wiley Online Library (***). DOI 10.1002/ecj.11477

关键词： gesture recognition human interface information projection projector-camera system

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Autocalibration of a projector-camera system

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 2005年第12期27卷 1845-1855页

作者： Okatani, T Deguchi, K Tohoku Univ Grad Sch Informat Sci Aoba Ku Sendai Miyagi 9808579 Japan

This paper presents a method for calibrating a projector-camera system that consists of multiple projectors (or multiple poses of a single projector), a camera, and a planar screen. We consider the problem of estimating the homography between the screen and the image plane of the camera or the screen-camera homography, in the case where there is no prior knowledge regarding the screen surface that enables the direct computation of the homography. It is assumed that the pose of each projector is unknown while its internal geometry is known. Subsequently, it is shown that the screen-camera homography can be determined from only the images projected by the projectors and then obtained by the camera, up to a transformation with four degrees of freedom. This transformation corresponds to arbitrariness in choosing a two-dimensional coordinate system on the screen surface and when this coordinate system is chosen in some manner, the screen-camera homography as well as the unknown poses of the projectors can be uniquely determined. A noniterative algorithm is presented, which computes the homography from three or more images. Several experimental results on synthetic as well as real images are shown to demonstrate the effectiveness of the method.

关键词： camera calibration imaging geometry projector-camera system autocalibration homography

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Attention retargeting using saliency map and projector-camera system in real space

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IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING 2019年第6期14卷 853-861页

作者： Takimoto, Hironori Yamamoto, Katsumi Kanagawa, Akihiro Kishihara, Mitsuyoshi Okubo, Kensuke Okayama Prefectural Univ Fac Comp Sci & Syst Engn 111 Kuboki Soja Okayama 7191197 Japan

Many attention-retargeting methods based on the visual saliency model of bottom-up attention for guiding human attention to target regions have recently been proposed. However, existing attention-retargeting methods focus on only modulating an image or a video presented to a display. It is difficult for the existing methods to guide humans' attention to objects in the real space. In this paper, we propose an appearance control method using a projector-camera system to realize attention retargeting in real space. The ideal appearance for attention retargeting is estimated on the basis of reverse engineering of the visual saliency map theory. Our system then projects an optimum light pattern calculated from the difference between the ideal appearance and current appearance in real space. Attention retargeting to the plane of real space is addressed as an initial step of our research. As a result, our attention-retargeting method can effectively control an appearance in real space for attention retargeting compared with spot light projection. (c) 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

关键词： attention retargeting visual attention saliency map projector-camera system

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A Monocular projector-camera system Using Modular Architecture

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2023年第12期29卷 5586-5592页

作者： Yamamoto, Kenta Iwai, Daisuke Tani, Ikuho Sato, Kosuke Osaka Univ Grad Sch Engn Sci Osaka 5650871 Japan

This paper presents a monocular projector-camera (procam) system using modular architecture based on relay optics. Conventional coaxial procam systems cannot support (1) online changes to lens settings (zoom and focus) and (2) wide-angle projection mapping. We develop design guidelines for a proposed procam system that would solve these restrictions and address the proposed system's unique technical issue of crosstalk between the camera and projector pixels. We conducted experiments using prototypes to validate the feasibility of the proposed framework. First, we confirmed that the proposed crosstalk reduction technique worked well. Second, we found our technique could achieve correct alignment of a projected image onto a moving surface while changing the zoom and focus of the objective lens. The monocular procam system also achieved radiometric compensation where a surface texture was visually concealed by pixel-wise control of a projection color based on the captured results of offline color pattern projections. Finally, we demonstrated the high expandability of our modular architecture, through the creation of a high dynamic range projection.

关键词： Lenses cameras Relays Optics Mirrors Optical imaging Optical sensors Augmented reality projection mapping projector-camera system

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Spatial Calibration of Airborne Ultrasound Tactile Display and projector-camera system Using Fur Material 17

Spatial Calibration of Airborne Ultrasound Tactile Display a...

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11th International Conference on Tangible, Embedded, and Embodied Interaction (TEI)

作者： Ko, Shigo Itoh, Yuta Sugiura, Yuta Hoshi, Takayuki Sugimoto, Maki Keio Univ Hiyoshi 3-14-1 Yokohama Kanagawa Japan Univ Tokyo Hongo 7-3-1 Tokyo Japan

ISBN: (纸本)9781450346764

Airborne Ultrasound Tactile Displays (AUTD) are tactile displays that can generate vibrotactile sensation on human skin. Combining an AUTD with a projector camera system, it is possible to present synchronous visual and haptic stimuli that is physically aligned in the 3D space. To maintain the synchronous sensation as realistic as possible, an accurate crucial to spatial calibration between the AUTD and the projector-camera system is required. This paper thereby proposes a calibration method for the AUTD system by utilizing fur material to recognize the output focal points of an AUTD in the camera coordinate system. Our method simplifies the calibration procedure with calibration error of 2.63 mm.

关键词： Device Calibration Airborne Ultrasound Tactile Display projector-camera system

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