Light source

In order to see within closed objects devoid of ambient light, light is provided to the VE by a cold (low-heat-producing) light source. A fiber-optic light guide connects the light source with the VE. Light can then travel through the fiber optics of the VE insertion tube and illuminate the field of view at the distal tip. Light sources vary in their configuration and should be matched to the application at hand (Figure 4.15). For example, in field applications, compactness, portability, and battery operational capabilities are the major considerations. Light sources are available that weigh approximately

Figure 4.13 (See color insert following page 12.) A comparison of two views of the same internal thorax. On the left is a video-endoscopic image of thoracic contents using a forward view near-focus lens, while on the right the same thorax is imaged using a forward view far-focus lens.
Figure 4.14 Proximal end of videoendoscope showing the tip directional controls at the top with locking mechanisms and the imaging controls, including freeze frame, brightness, digital zoom, and store to disc controls. Additional settings are adjustable in the menu function.

4 lb, about the size of a hair dryer, and can be operated by battery. Other portable light sources are handheld, like a flashlight. These basic light sources are simple in their operational aspects as well with an on/off control and a brightness control. The light is typically derived from a halogen bulb. Portable light sources may also use LED lights for illumination. If the endoscopic application is to be conducted in a laboratory setting, additional light source options become available. Higher-wattage light is available as well as additional controls such as filters, exposure indexing, and air pumps.

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