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A USB microscope is a low-powered digital microscope which connects to a computer, normally via a USB port. They are widely available at low cost commercially. In essence USB microscopes are a webcam with a high-powered macro lens and generally do not use transmitted light, but rely on incident light from in-built LEDs lights situated next to the lens. The light reflected from the sample then enters the camera lens. Often however, the camera is sensitive enough not to need additional lighting. As the camera attaches directly to the USB port of a computer, eyepieces are not required and the images are shown directly on the monitor. They offer modest magnifications (up to about 200×) without the need to use eyepieces at very low cost, compared with conventional stereomicroscopes for example.〔("Introduction to Stereomicroscopy" ) by Paul E. Nothnagle, William Chambers, and Michael W. Davidson, ''Nikon MicroscopyU''.〕 The quality of the final image depends on the camera capacity or megapixels available with the system, varying from 1.3 MP, 2 MP, 5 MP and upwards, as well as operator skill and illumination quality. Both still images and videos can be recorded on most systems. The capacity of most USB microscopes is similar to that of most camera phones of about 2 megapixels. ==Usage== Images can be recorded and stored similar to a webcam on the computer. The camera is usually fitted with a light source, although extra sources (such as a fiber-optic light) can be used to highlight features of interest in the object. They generally offer a large depth of field and a range of magnification when examining the image file on the computer. The camera is so sensitive that it will generally work without the need for any extra light source. USB microscopes are most useful when examining flat objects such as coins, printed circuit boards, or documents such as banknotes, but can be used on surfaces of irregular shape such as fibres owing to the high depth of field. Their use is generally similar to that of a reflection optical microscope or a stereo microscope. USB microscopes offer the great advantage of being much less bulky than a conventional stereo microscope so can be used in the field, attached to a laptop computer. They are also useful in examining large items ''in situ'' where use of a conventional microscope would be difficult if not impossible. Such devices are useful in Forensic engineering where large fracture surfaces need direct examination, an application where conventional light microscopes are restricted in use. They are normally hand held for this application, but can also be mounted in a small clamp (usually provided). Separate clamps with better control are also available separately. Larger versions have their own dedicated stand. Simple ways in which the microscope can be used is a comparison of salt crystals, such as sea salt and table salt. A common millimeter scale at the tops of the micrographs show the smaller size of the cubic table salt crystals. The good depth of field available is shown by USB micrographs of a Salvia officinalis or Sage leaf. USB microscopes are also being used in crime scene investigation units. Many USB microscopes can view objects from a short distance, allowing sensitive crime scene evidence to be investigated without actually contaminating the evidence in any way. They also find use in medical application such as ENT examinations.〔(ENT application ).〕 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「USB microscope」の詳細全文を読む スポンサード リンク
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