USB microscope

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 for use at home or in commerce. Their cost varies in the range of tens to thousands of dollars. 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. However, the camera is usually 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 usually offer modest magnifications (about 1× to 200×) without the need to use eyepieces at very low cost, at least compared to conventional stereomicroscopes for example. 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.

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 advantage of being much less bulky than a conventional stereo microscope, so they 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.

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Wikipedia