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Document cameras, also known as visual presenters, visualisers (in the United Kingdom), digital overheads, or docucams, are real-time image capture devices for displaying an object to a large audience. Like an opaque projector, a document camera is able to magnify and project the images of actual, three-dimensional objects, as well as transparencies.〔.〕 They are, in essence, high resolution web cams, mounted on arms so as to facilitate their placement over a page. This allows a teacher, lecturer or presenter to write on a sheet of paper or to display a two or three-dimensional object while the audience watches. Theoretically, all objects can be displayed by a document camera. Most objects are simply placed under the camera. The camera takes the picture which in turn produces a live picture using a projector. Different types of document camera/visualizer allow great flexibility in terms of placement of objects. Larger objects, for example, can simply be placed in front of the camera and the camera rotated as necessary,or a ceiling mounted document camera can also be used to allow a larger working area to be used. Typical applications for a document camera include: * Lecture hall or classroom use * Presentation of material in conferences, meetings and training sessions * Videoconferencing and telepresence * Presentation of evidence in courtrooms * Various medical applications (telemedicine, telepathology, display of x-rays) Document cameras replaced epidiascopes and overhead projectors, which were formerly used for this purpose. By means of the zoom feature a document camera can enlarge the small print in books and project a printed page as if it were a traditional transparency. Also the room lighting does not have to be darkened to operate a document camera; in a classroom setting this is an asset.〔.〕 Most document cameras can also send a video signal to a computer via USB cable. Sometimes document cameras are connected to an interactive whiteboard instead of a standard screen. Some document cameras can be supplied with an accessory so that they can be used with a microscope. According to recent research by Futuresource Consulting over 11k visualisers were sold in UK in 2008 and Futuresource forecasts that over 17,000 will be sold in 2009. The market is valued at £12 million in 2009 increasing 53% in 2010 to £18 million. One in 30 UK school classrooms now have a visualiser. That is expected to increase to 1 in 10 by 2010. , the most economical document cameras capture XGA resolution images of 1024×768 pixels. Document cameras that capture SXGA images capture a resolution of 1280×1024 which equates to 66% more pixels than XGA images. Higher-resolution images contain more (smaller) pixels and provide sharper detail. UXGA is considered high-definition and equates to 1920×1080 pixels. == History == Document cameras were developed to meet an increased demand for the ability to project and present original documents, plans, drawings and objects directly, rather than necessitating the prior preparation, that would be required for their use as part of an overhead projector based presentation. The first Visualizer/document camera were developed by the companies WolfVision and Elmo and were launched at the photokina Trade Fair in 1988.〔http://www.wolfvision.com/visualizer/index.php/en/company-1/history〕 The widespread use of computers, projectors, and popular presentation programs such as Microsoft Powerpoint in meeting rooms, meant that overhead projectors became less frequently used. Document cameras continue to provide a convenient and flexible way of allowing documents, books or slides to be spontaneously displayed during presentations as required. The first attempts and prototypes were mostly simple video cameras on a copy stand. During the mid-1970s these were assembled and equipped with additional lighting to ensure that they were able to operate in darkened rooms, and also to provide a consistent quality of projected image. The technology of video cameras during this time, was a key factor in the development of document camera systems. Document cameras have also frequently benefited from developments in other industries, which also facilitated significant advances in the field of document camera technology. A good example of this is the technology used in photographic equipment, which has contributed much to the development of the document camera as a high quality presentation tool. At the end of the 1990s progressive scan cameras were introduced. Many visualizers available on the market today are capable of at least 30 frames per second output, which ensures high quality imaging and smoothness of motion in all resolutions and aspect ratios. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「document camera」の詳細全文を読む スポンサード リンク
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